Neuro Flashcards
A “golf tee sign” observed on a myelogram is consistent with…
Intradural (subarachnoid) but extramedullary lesion
Best diagnostic to identify extradural lesions - CT, CT+ contrast or MRI?
MRI
Intramedullary spinal lesions - causes, differential diagnoses
An intramedullary pattern is typically associated with spinal cord edema, expansile parenchymal masses, or intraparenchymal hemorrhage. Differential diagnoses include fibrocartilaginous emboli, neoplasia (e.g., astrocytoma, lymphosarcoma), inflammatory disorders (e.g., granulomatous meningoencephalitis in dogs, feline infectious peritonitis [FIP] in cats), and trauma (e.g., hemorrhage, edema)
Intradural/extramedullary spinal lesions are often caused by…
Intradural/extramedullary patterns are most often associated with neoplasia, primarily meningiomas and nerve sheath tumors
Extradural-pattern spinal lesions are often caused by…
Intervertebral disk extrusion/protrusion is the most common cause of an extradural myelographic pattern. Other causes of extradural patterns include vertebral fracture/luxation, congenital vertebral anomalies, hypertrophied soft tissue structures (e.g., interarcuate ligament, synovial membranes), extradural hemorrhage, vertebral neoplasia, and soft tissue neoplasia (e.g., feline lymphosarcoma)
Most common site for CSF tap; advantage/disadvantage
cerebellomedullary cistern (cisternal tap).
Easy to obtain CSF
If needle penetrates the cord parenchyma and reached the ventral aspect it can lacerate the basilar artery (very serious)
Lumbar CSF tap location for large dogs vs small dogs/cats
Advantages
Large dogs: L4-5
Small dogs/cats: L5-6
Safer than cisternal tap; needle intentionally penetrates the spinal cord but usually does not cause adverse effects
CSF cellular abnormalities associated with Granulomatous Meningoencephalitis
Mononuclear cell pleocytosis refers to a predominance of lymphocytes or macrophages in the CSF.
7 components of the neurologic exam
1) Mentation
2) Gait
3) Posture
4) Cranial Nerves
5) Postural Reactions (proprioception)
6) Spinal Reflexes
7) Nociception
Define Obtunded Vs Stuporous Vs Comatose
Obtunded animals tend to appear depressed, listless, and disinterested in spontaneous activity. Although these patients often appear drowsy, they are easily aroused with a minor stimulus (vocal cues, other noises). Unlike other forms of depression (e.g., those due to metabolic disease), obtunded patients are often described as appearing “out of it.”
Stupor describes a dog or cat that is not conscious but can be aroused with a strong stimulus (e.g., toe pinch).
Coma refers to a state of unconsciousness that persists even after the application of a strong stimulus
Mental statuses most commonly associated with brain stem disease
Stupor or coma
Mental status most commonly associated with forebrain disease (cerebellum and diencephalon)
Obtunded
Trigeminal nerve functions
•Somatic motor to muscles of mastication
•Somatic motor to tensor tympani muscle
•Sensory to most of face
Trochlear nerve function (CN IV)
Somatic motor to dorsal oblique muscle of the eye
Functions of Oculomotor nerve (CN III)
•Somatic motor to most of the extraocular muscles (dorsal, medial, ventral rectus; ventral oblique; levator palpebrae superioris)
•Parasympathetic innervation to pupil (pupillary light response)
Functions of Abducent nerve (CN VI)
Somatic motor to lateral rectus and retractor bulbi muscles (extraocular)
Facial nerve functions (CN VII)
•Somatic motor to muscles of facial expression
•Somatic motor to stapedius muscle
•Parasympathetic innervation to salivary glands (mandibular, sublingual)a and lacrimal, palatine, and nasal glandsb
•Sensory to inner pinna
•Sensory (mechanoreception, thermal) and taste to rostral two-thirds of tongue (chorda tympani nerve)c
Functions of glossopharyngeal, Vagus and Accessory nerves (CN IX, X and XI)
•Somatic motor for laryngeal and pharyngeal function (nucleus ambiguus)
•Parasympathetic innervation to salivary glands (parotid and zygomatic—CN IX)d
•Parasympathetic innervation of viscera (CN X)
•Sensory innervation of pharynx (CN IX and X)
•Sensory and taste to caudal one-third of tongue (CN IX)
Explain Schiff-Sherington posture
This posture is characterized by rigid extension of the thoracic limbs (with preservation of thoracic limb function) accompanied by pelvic limb paresis or plegia. Increased extensor tone to the thoracic limbs is due to the interruption of a group of cells in the lumbar gray matter called border cells, or of those cells’ cranially directed axonal processes (Fig. 38.18). These cells project their axons cranially to tonically inhibit the lower motor neurons (LMNs) of thoracic limb extensor muscles. When the border cells or their axons are disrupted as the result of a spinal cord lesion caudal to the cervical intumescence region, the thoracic limb extensors are “released” from this tonic inhibition. The thoracic limbs have excessive extensor tone (especially when the patient is in lateral recumbency), but there are no associated thoracic limb neurologic deficits. Most patients with Schiff-Sherrington posture have T3-L3 myelopathies, probably because this is a very common neuroanatomic presentation, and most are nonambulatory in the pelvic limbs. This posture is an anatomic phenomenon without prognostic significance. Dogs and cats with lower lumbar spinal cord lesions can also display this posture as the result of interruption of the border cells directly (they are located in the dorsolateral ventral gray matter from L1–L7 spinal cord segments). As there is no brain involvement with this phenomenon, it should not be confused with other postures that display thoracic limb hyperextension (i.e., decerebrate and decerebellate rigidity).
3 types of ataxia
Sensory, vestibular and cerebellar
Wide, side-to-side head excursions during ambulation. Type of ataxia
Vestibular (peripheral or central), bilateral
•Due to interference with ascending spinal cord proprioceptive pathways
•Manifested as a swaying gait
•Toe dragging may be evident
•Clumsy gait
•May fall when turning
Type of ataxia ?
Sensory
Dorsal column (spinal cord) responsible for conscious proprioception. Name the three fascicles and where they are represented in the brain
Fasciculus gracilis, cuneatus and spinomedulary tract. Represented in the contra lateral cerebral cortex
Spinal fascicles conveying unconscious proprioception; where are they represented in the brain
Spinocerebellar tract; cerebellum (no cortex involvement, so no consciousness)
Clonus elicited during tendon reflex tenting is indicative of
Chronic UMN disease
The biceps tendon reflex assesses which nerve? From which cervical vertebral segments does this nerve originate?
Musculoutaneous N; C6-8
The triceps tendon reflex tests which nerves? On which spinal segments does this nerve originate?
Radial nerve, C7 - T1
The patellar tendon reflex assesses the integrity of which nerve? On which spinal segments does this nerve originate?
Femoral nerve, L4-L6
The gastrocnemius tendon reflex assesses the integrity which nerve? On which spinal segments does this nerve originate?
Sciatic nerve, L6-S2
The panniculus reflex assesses the integrity of which nerve? On which spinal segments does this nerve originate?
Lateral thoracic nerve, C8-T1
The perineal reflex assesses the integrity of which nerves? On which spinal segments do these nerves originate?
Sacral spinal cord S1-S3 and various branches of the pudendal nerve
Define spinal shock and it’s typical presentation in dogs
Spinal shock refers to a transient lack of reflex activity caudal to a severe spinal cord lesion; this phenomenon of hypotonia and hyporeflexia with lesions that should cause UMN signs is uncommon and short-lived in dogs and cats compared with humans. A form of this phenomenon may frequently be observed in dogs with spinal cord infarction (fibrocartilaginous embolic myelopathy) in the T3–L3 spinal cord region. These patients typically exhibit UMN signs with the exception of poor withdrawal reflexes; the withdrawal reflex returns to normal within 72 hours
Most important spinal pain pathway and dogs and cats
Spinothalamic tract
IV fluid of choice during cerebral surgery; why
Normal Saline. The blood-brain barrier prevents colloidosmotic pressure from working in the brain, so osmotic pressure becomes more important (sodium).
Three most common types of craniotomy
Transfrontal, rostrotentorial and suboccipital
Important vascular structures to avoid during brain surgery
Dorsal sagittal sinus and transverse sinuses
Most common reason to perform a transfrontal craniotomy in the dog
To remove meningiomas in the olfactory bulb
Surgical approach to relieve Chiari-like malformation
Suboccipital craniotomy
Most common immediate postoperative complications after a craniotomy
Swelling, hemorrhage and cardiovascular dysfunction (brainstem surgery)
Most common and second most common brain tumor in dogs
Meningiomas, followed by gliomas
Most common and severe complication of brain tumor removal in dogs / percentage; mortality rate
Pneumonia, 20%; 50% mortality
Is the reparation of a feline intracranial meningioma advisable?
Yes, the success rate is high and the same as for the initial surgery
Prognosis for secondary brain tumors in dogs and cats
Poor
A “two engine” gait is typically associated with …
Caudal cervical myelopathy. Ambulatory patients with caudal cervical myelopathy tend to have obvious pelvic limb weakness and ataxia, with less severe, sometimes even subtle, thoracic limb dysfunction. In many such cases, the thoracic limbs move with short, stilted steps, whereas the pelvic limbs display obvious ataxia
Serious thoracic limb neurological deficits are more typically associated with Cranial or caudal myelopathy?
Cranial
Define central cord syndrome - affected region, expected neuro deficits, most common causes
A phenomenon called central cord syndrome is sometimes appreciated in dogs and cats with caudal cervical spinal cord lesions that are confined to the central region of the cord. In this syndrome, the thoracic limbs display severe lower motor neuron (LMN) weakness, but the pelvic limbs are minimally affected or neurologically normal. This occurs because the centrally located lesion interferes with LMNs innervating the thoracic limbs, but it spares the more peripherally located white matter upper motor tracts that innervate the pelvic limb LMNs. Central cord syndrome is most commonly associated with intraaxial lesions like syringomyelia and neoplasia
Phrenic nerve - UMN or LMN? Originates on what spinal segments?
LMN, C5-7
Explain the phenomenon or abdominal breathing in the context of cervical spinal lesion
Descending tracts from the medullary respiratory centers traverse the cervical spinal cord to innervate the phrenic nerve LMNs (C5–C7) and the LMNs of intercostal muscles in the thoracic spinal cord. Damage to these tracts can lead to respiratory compromise. Caudal cervical spinal cord lesions that spare innervation to the phrenic nerve LMNs (e.g., lesions caudal to the C5–C7 segments) but disrupt normal activation of intercostal LMNs can lead to the phenomenon of abdominal breathing. In this scenario, the diaphragm bears the sole burden of moving air through the lungs because of the denervated chest wall, and this motion causes the abdomen to visibly move back and forth during respiration.
Explain severe hypotension in the context of cervical myelopathies
Tonic input to the sympathetic LMNs in the thoracolumbar spinal cord that maintain normal blood pressure is provided by neurons in the medulla (rostroventrolateral medulla). Because these medullary neurons send their processes through the cervical spinal cord, cervical myelopathies may be associated with severe hypotension.
Advantages and disadvantages of a dorsal versus ventral approach the cervical spinal cord
Ventral approach - technically less demanding, more bone available for implant placement, limited exposure of the spinal cord, higher likelihood of severe venous sinus hemorrhage.
Dorsal approach - allows wide decompression / access to the dorsal and lateral aspect of the spinal cord, technically more difficult, slower patient recovery, minimal stock for implant placement (articular facets)
What joint in the vertebral column lacks an intravertebral disc?
C1-C2
Name the three ligaments connecting the dens of the Axis to the Atlas
Apical ligament, Alar ligaments and transverse ligament
muscles that must be divided during a ventral approach to the cervical vertebral column
Sternocephalicus and sternohyoideus and longus colli muscles
Two paired muscles to be split and one to elevate during the dorsal approach to the cranial cervical vertebral column
rectus capitis dorsalis muscle cranially and the spinalis cervicis muscle caudally ; elevate the multifidus muscle (C4-C7)
What are the typical differences in the clinical presentation of Type 1 IVDD and HNPE ?
HNPE cases are characteristically peracute to acute and tend to cause fairly severe neurologic dysfunction (nonambulatory tetraparesis or tetraplegia), often without obvious evidence of cervical hyperesthesia; this contrasts with typical calcified type I extrusions, which commonly lead to substantial cervical hyperesthesia that is less frequently associated with severe neurologic dysfunction
Normal and abnormal appearance of the nucleus pulposus on T2-weighed MRI
Normal - hyperintense (The annulus is hypointense)
Degenerative – hypointense
What is the expected clinical presentation in a dog with a cervical type I disk extrusion with a predominant lateral displacement of disk material?
Unilateral cervical pain with or without lameness (Root signature) without proprioceptive or motor deficits
What is the preferred diagnostic modality for the diagnosis of syringomyelia?
MRI
A hyperintense “seagull” appearance of extruded disk material on T2-weighed MRI is consistent with…
HNPE
Inflammatory/infectious conditions that mimic cervical disc extrusion/protrusion
Other diseases that can cause similar or identical signs of cervical disc extrusion/protrusion include inflammatory/infectious conditions (e.g., corticosteroid-responsive meningitis, discospondylitis, granulomatous meningoencephalomyelitis), syringomyelia, traumatic fracture/luxation, neoplasia, and congenital abnormalities (e.g., Chiari-like malformation [CLM], AA instability, atlanto-occipital overlapping [AOO]).
Percentage of dogs likely to experience a positive response to conservative management of type I IVDD characterized by cervical pain with mild to no neuro deficits. Percentage of recurrences
50 to 70% Strict cage restriction, NSAIDs (no steroids) and possibly adjunct analgesics such as tramadol or pregabalin; 30% recurrence
Can HNPE be managed medically?
Yes (Limited number of reported cases). The biochemical nature of the extruded material allows for a more rapid resorption compared with calcified disk material.
Clinical criteria for surgical treatment of type 1IVDD
Repeated episodes of pain, pain that is not responding to medical therapy or severe neurologic deficits (tetraparesis, tetraplegia)
Surgical procedure of choice for a cervical disc extrusion
Ventral slot
Most common complications associated with surgery for cervical disc extrusion/protrusions
Transient neurologic worsening and venous sinus hemorrhage
Overall success rate of surgically managed type 1 cervical disc extrusions in small and large breed Nonambulatory tetra paretic or tetraplegic dogs. Time until return to ambulation
99%; 1 week
What are the two distinct clinical entities associated with the term cervical spondylomyelopathy (CSM), also known as “wobbler syndrome”
Disc associated CSM (DA-CSM) and Osseous-associated CSM (OA-CSM)
Typical signalment of dogs affected by DA-CSM; most commonly affected intervertebral segments
Middle-age to older, large and giant breed dogs (Doberman pinchers). Typically affecting the caudal cervical vertebrae, particularly C5-C6, C6-C7
Pathoanatomy of DA-CSM
Combination of vertebral malformation and malarticulation typically affecting the caudal cervical vertebrae and associated soft tissue structures (disc, articular process joint capsules, dorsal longitudinal ligament and ligamentum flavum). Soft tissue structures become hypertrophied, leading to impingement of the spinal cord
Pathoanatomy of OA – CSM
Congenital bony stenosis of cervical vertebrae most commonly occurring in young large or giant breed dogs (usually 1–3 years, great Dane, mastiff, Bernese mountain dog, Doberman pincher, basset hound). Typically called “ wobbler syndrome” ; has several distinguishing characteristics from DA-CSM. Primarily bony proliferation associated with the articular processes and associated joint capsule, as well as the dorsal lamina and pedicles, usually without substantial disc protrusion. Cystic enlargement of the articular process joint capsule (extradural synovial cyst) may also be observed.
Vertebral segments most commonly associated with OA-CSM
C2-C3 through T1-T2
Breeds commonly affected by DA – CSM
Doberman pincher, Rottweiler
Typical signalment of patients affected by OA-CSM
Young adult giant breeds (great Dane, mastiff) with progressive signs of cervical myelopathy
Typical clinical signs associated with cases of DA-CSM and OA-CSM
Signs of caudal cervical myelopathy with pelvic limbs usually more obviously affected than thoracic limbs. If ambulatory, the patient typically exhibits a stiff, choppy, shuffling thoracic limb gait and an ataxic, wide-based pelvic limb gate (two engine gait). Thoracic limb posture characterized by elbow abduction and internal rotation of the digits. Signs of proprioceptive deficits maybe exacerbated by making the patient walk with a slightly extended head/neck. Patient may be reluctant to walk in this position.
Preferred diagnostic modality and positioning for the diagnosis of CSM
MRI with linear traction views
Possible sources of compression in a patient with DA-CSM (disk associated cervical spondylomyelopathy)
Ventral compression from a malaligned vertebral body, Protruded dorsal annulus, hypertrophied dorsal longitudinal ligament, dorsal compression from hypertrophied ligamentum flavum, lateral compression from hypertrophied articular facets and associated joint capsule tissue.
Can medical therapy be attempted for the treatment of a CSM? If so, what are the recommendations, success rate and the chance of recurrence?
Yes, medical treatment consisting of cage confinement for 3 to 4 weeks, anti-inflammatory medication (prednisone) and potentially the use of a neck brace Is effective in approximately 53% of the cases. Median survival for medical management 3.6 years compared with 5 years for surgical management. Patient treated medically and more likely to be euthanized due to worsening neurologic condition than those surgically treated.
What is the currently favored surgical procedure for the treatment of DA-CSM?
Distraction-stabilization procedures (Not ventral slot) using pin or screw placement into vertebral bodies with a PMMA bridge, and PMMA “plug” insertion into the distracted ventral slot.
What is the surgical procedure of choice for the treatment of OA – CSM?
Dorsal laminectomy
Success rate of the distraction-stabilization techniques for the treatment of DA-CSM
70 to 90%
Four more common Craniocervical junction anomalies (CJA’s)
Chiari-like malformation (CLM)
AA instability
Atlanto-occipital overlapping (AOO)
Dorsal compression at C1–C2
Most common cause of atlantoaxial instability
Hypoplasia or aplasia of the dens
Typical signalment of a dog affected by AA instability
Miniature toy breed dog, younger than two years of age. Yorkshire terrier, Pomeranian, toy poodle, Chihuahua, Pekinese. May occur in cats.
Typical clinical presentation for a dog affected by AA instability, AOO or C-1-C2 dorsal compression
neck pain and varying degrees of ataxia of all four limbs. Nonambulatory tetraparesis and tetraplegia occur in severe cases.
Recommended diagnostic approach to craniocervical junction anomalies CJA’s; Advantages/disadvantages of diagnostics
Radiographs typically diagnose AA instability but require stress views which can be dangerous. MRI is much safer but does not offer a good bone detail. CT offers good detail saw MRI followed by CT is a current recommendation.
Potential complications of AA instability surgery; rationale
Respiratory and cardiac arrest due to damage to brainstem centers
Upper respiratory function disorder such as gagging, coughing and laryngeal paralysis
Aspiration pneumonia, likely due to pharyngeal disorder
Success rate of AA instability surgical treatment; poor prognostic indicators
Above 80%
Length of clinical disease prior to surgery and severity of clinical dysfunction
Most common sites for spinal Arachnoid diverticula
Craniocervical (most commonly over C2 C3) and caudal thoracic regions. Typically located on the dorsal or dorsal lateral aspect of the spinal cord
Breed commonly affected by spinal arachnoid diverticula
Rottweiler, typically in the cranial cervical region. Also pugs and French bulldogs
Typical clinical presentation for dogs with spinal arachnoid diverticulum
Slowly Progressive ataxia and tetraparesis
Typical cerebrospinal fluid analysis results for a patient with spinal subarachnoid diverticula
Mild mononuclear pleocytosis with elevated protein concentration
Most common extradural tumors in dogs
Osteosarcoma, chondrosarcoma, myeloma, fibrosarcoma and hemangiosarcoma
Most common spinal tumor of cats
Lymphosarcoma (primary or metastatic)
Most common intradural/extra medullary neoplasm in dogs
Meningiomas and MNST‘s
Most common site for spinal meningiomas and MNST
Cervical intumescence
Most common clinical feature of extradural and intradural/extra medullary spinal neoplasia
Spinal hyperesthesia
Most common cervical spinal disorders associated with a progressive neurologic decline
Type II disc protrusion, Syringomyelia, CCSM, CJA’s, infectious/inflammatory disorders and neoplasia
Spinal tumors amenable to chemotherapy
Liposarcoma, myeloma, meningioma & glioma
Prognosis for dogs with Spinal MNST’s
Poor, with median postoperative survival of approximately 5 to 6 months. Disease-free interval of approximately one month.
Most common site for cervical fracture’s
C1-C2
Most likely diagnosis for sudden onset of neurological deficits without history of trauma and without spinal hyperesthesia
Fibrocartilagenous embolism
Current thoughts regarding the use of corticosteroids and polyethylene glycol in patients with spinal cord trauma
Corticosteroids have not been shown to be beneficial and significantly increase the risk of gastrointestinal ulcers. PEG has not been shown to be a benefit either.
What are the two primary objectives in the surgical treatment of spinal fractures? Which one should have priority?
Stabilization and decompression. The most pressing goal is stabilization
Bone reduction forcep helpful during stabilization of spinal fractures
ASIF small fragment reduction forcep
Define hemilaminectomy and dorsal laminectomy
Hemi laminectomy is the unilateral removal of the lamina, articular processes and part of the pedicle. Dorsal laminectomy is removal of the dorsal lamina bilaterally, including removal of the dorsal spinous process
Thoracolumbar myelopathies are more commonly associated with upper or lower motor neuron bladder?
UMN
UMN Bladder dysfunction is more common with cervical or thoracolumbar myelopathy?
Thoracolumbar
Thoracic segments in which the articular processes are oriented dorso-eventually
T1-T10
From which intravertebral joint segment caudally are the articular processes located in a sagittal plane, with the cranial articular process joint surface facing medially in the caudal articular process joint surface facing laterally
T10-T11
Anticlinal vertebra
T11
Important surgical landmark for implant placement on the lumbar vertebrae
The “elbow” of the transverse process, oriented cranially and slightly ventral lateral
The order muscles are encountered on a dorsal approach to the thoracic vertebral column
Trapezius, rhomboideus, serratus dorsalis, spinallis and semispinalis
What structures must a surgeon be careful to preserve while performing the tenotomy of the longissimus lumborum muscles during a thoracolumbar approach to the vertebral column
Spinal nerves
The low incidence of intravertebral disc disease cranial to T10 – 11 maybe attributed to which anatomical structure?
Intercapital ligament
Most common site for type one disc extrusion in small breed dogs
T12-T13; T13-L1
Most common site for type I intravertebral disc extrusion in large dogs
L1-L2; L2-L3
Does the degree of spinal cord compression or the presence of multiple disc extrusion‘s affect prognosis For return to normal function in dogs with type one IVDD?
No
Typical indication for a lateral corpectomy
Tape 2 IVDD
Define the Cobb angle it how it applies to clinical practice
The Cobb angle is derived from the intersection of two lines: one of the cranial aspect of the kyphotic vertebral segment and the other on the caudal aspect of the segment. Angles above 35° are associated with a higher chance of neurologic dysfunction in dogs with vertebral Kyphoscoliosis formation
Most common methods employed in the stabilization of kyphoscoliotic vertebral segments
Modified segmental spinal fixation (spinal stapling) and vertebral body pins with PMMA
Spinal Nephroblastoma - Typical location, predisposed breed and age range
Thoracolumbar region, typically between 10th thoracic and third lumbar vertebrae, typically extra medullary intradural, six months to three years of age, German shepherds
Extradural spinal mass in a young cat. Most likely diagnosis
Lymphoma
Define “pseudohypereflexia”
The patellar reflex may appear hyperreflexive when the inhibitory action of the stifle flexion muscle group is removed by disruption of the nerve supply to these muscles. This is frequently the case with cauda equina syndrome, when contributing roots to the sciatic nerves are affected.
Nerve injury classification - explain
Class I: neurapraxia
Class II: axonotmesis
Class III: neurotmesis
Are dogs with transitional lumbosacral vertebrae more predisposed to DLSS?
Dogs with transitional lumbosacral vertebrae are eight times as likely to develop DLSS
Breed most commonly affected by degenerative lumbosacral stenosis (DLSS); typical clinical presentation
German Shepherd, presumably due to the high incidence of transitional lumbosacral vertebrae and articular facet joint tropism (asymmetry between left and right processes)
Chronic history of pain and unilateral or bilateral lameness with or without pelvic limb weakness. Difficulty rising, inability or unwillingness to climb stairs, scuffing of the toenails in the back limbs, muscle atrophy of the caudal thighs, urinary or fecal incontinence, abnormal tail carriage, biting/chewing at the base of the tail or paws
Typical physical examination findings in patients with DLSS
Lumbosacral pain on palpation (Most common finding), progressive loss of pelvic limb proprioception, followed by loss of motor function (weakness) typically associated with the area of the sciatic nerve. Deficient pelvic limb withdrawal reflex at the level of the hock[(Flexion of the hip and stifle remain normal)
Preferred diagnostic procedures for the diagnosis of DLSS
MRI, followed by Discography and epidurography
Typical age of dogs affected by solitary or multiple cartilaginous exostosis or spinal lymphosarcoma
Less than 1 year
Most likely cause for lysis of an intervertebral foramen
Nerve root tumor (neurofibroma, meningioma)
Are steroids indicated prior to spinal surgery?
No, steroids have not been shown to protect spinal tissue/nerve roots.
MRI features associated with canine cognitive dysfunction syndrome
Decreased interthalamic adhesion thickness; enlarged ventricles, brain atrophy
Protein that accumulates in the brains humans and dogs with cognitive dysfunction syndrome
Neurotoxic Beta amyloid (neurotoxic A-beta)
The main proposed biochemical imbalance observed in the brains of dogs and humans with cognitive dysfunction syndrome
Catecholamine disfunction
drug to improve cognitive function and decrease hyperexcitability in animal models of cognitive disfunction.
Levetiracetam; potential mechanisms of action include improved central nervous system mitochondrial function and associated improved synaptic transmission come out inhibition of beta amyloid-induced astrocyte glutamate release.
Area of the spinal cord typically affected by degenerative myelopathy
T3-L3
Only definitive diagnostic test for degenerative myelopathy
Necropsy
Major differential diagnosis for degenerative myelopathy
Type II IVDD
Most common causes of strokes in dogs
Hypothyroidism, followed by chronic renal disease and hyperadrenocorticism
Breed most commonly affected by cerebellar ischemic/vascular events. Why…
Cavalier King Charles spaniel
Presumably due to this breeds propensity to develop heart disease, inherited platelet abnormalities, or to local aberrations in regional arterial blood flow resulting in Chiari like malformations (CLMs)
Most common cause of myelopathy in schnauzer
FCE
Typical clinical presentation of FCE
Set an onset of acute discomfort during exercise, followed by non-progressive paraparesis or paralysis without discomfort. Focal discomfort can typically be elicited at the site of infarct in the first 12 hours.
Most common Nuro anatomic localization of FCE
T3-L3, followed by L4-S1
Typical T2-weighed appearance of FCE on MRI
Hyperintense
Contrast enhancement varies depending on timing Since onset
Acute onset of T3-L3 Myelopathy with spinal hyperesthesia. Most likely diagnosis in Staffordshire terrier versus border collie
Staffordshire terrier – FCE
Border collie - HNPE
C1-C5 spinal compressive lesion - FCE or HNPE more likely?
HNPE
Histological character of GME
Perivascular infiltrates of primarily mononuclear cells (lymphocytes, macrophages and plasma cells)
Presumed etiology of GME
Autoimmune, specifically delayed type hypersensitivity reaction ( T cell mediated)
Brain tissue most commonly affected by GME, three clinical forms
White matter. Focal, multifocal and ocular
Necrotizing encephalitis (NE) – two distinct disorders, hystopathological features
Necrotizing Meningoencephalitis (NME) and necrotizing Leukoencephalitis (NLE). Both similar and characterized by multiple cavitary necrotic nonsuppurative inflammatory brain lesions that involve both gray and white matter.
Breeds most commonly affected by necrotizing encephalitis
Pug, Maltese
Most common clinical signs associated with GME
Seizures, cerebellovestibular disfunction, Cervical hyperesthesia
The most common type of meningitis encountered in veterinary practice
Steroid responsive meningitis (SRMA)
Typical signalment in the presentation of dogs with steroid responsive meningitis (SRMA)
Young (less than two years old) , medium to large breed (boxers, Bernese mountain dogs). Acute onset of cervical hyperesthesia accompanied by lethargy and a stiff gait.
CSF fluid results expected in a patient with SRMA
Marked polymorphonuclear pleocytosis (predominantly or exclusively non-degenerative neutrophils), elevated protein concentration
Most common causative agents of discospondylitis
Staphylococcus spp. ( S. aureus; S. pseudointermedius); Streptococcus, Brucella, Aspergillus
Typical signalment of dogs affected by discospondylitis
Medium to giant breed (especially great Danes), any age but more commonly after 10 years of age
Discospondylitis - Typical clinical presentation, common location
Gradual onset of lethargy (Occasionally acute), spinal hyperesthesia, stilted pelvic limb gait if lumbosacral, fever and anorexia
Lumbosacral junction
Proposed site of origin for bacteria causing discospondylitis
Urinary bladder
Most common peripheral nervous system disorders encountered in dogs and cats
Myasthenia gravis, autoimmune polymyositis, polyradiculoneuritis, tick paralysis
Nerve typically biopsied when trying to diagnose peripheral pelvic limb neuropathies
Common peroneal nerve and cranialis tibialis nerve
Pathophysiology of myasthenia gravis
Autoimmune disorder characterized by the production of antibodies against nicotinic acetylcholine receptors of skeletal muscle. The typical presentation includes antibody attack in skeletal muscle and weakness which tends to worsen with exercise.
Megaesophagus is also common in dogs and rare and cats (large amount of striated muscle in dog’s esophagus.)
Common feline tumor associated with myasthenia gravis
Mediastinal tumor (thymoma)
Typical medical therapy of myasthenia gravis
Anticholinesterase drugs (pyridostigmine or neostigmine), possible with immunosuppressive doses of prednisone
Factors associated with the development of auto immune polymyositis
Systemic lupus erythematosus, the use of trimethoprim sulfa drugs in Doberman pinschers and thymomas
Breeds most commonly affected by autoimmune polymyositis
Newfoundland and boxers. Newfoundland usually develop the condition early in life. Boxers typically develop the condition as a paraneoplastic syndrome
Common idiopathic inflammatory disorder of dogs similar to Guillian-Barre syndrome in people
Acute idiopathic polyradiculoneuritis
Pathophysiology and typical presentation of acute idiopathic polyradiculoneuritis
Idiopathic inflammatory disorder involving both axons and myelin of ventral nerve roots. Typical presentation includes acute development of lower motor neuron paresis/plegia, usually beginning in the pelvic limbs and eventually involving thoracic limbs. Spinal reflexes are typically absent. Proprioceptive placing reactions will be normal for as long as motor ability is still present.
Tick species responsible for tick paralysis
Dermacentor (North América) and Ixodes (Australia)
Six parts of the neurological exam
1) sensorium and behavioral
2) posture and gait
3) postural reactions
4) spinal reflexes, muscle tone, muscle mass
5) cranial nerves
6) cutaneous sensation
Anatomy and function of the reticular activating system
A collection of nuclei in the brainstem which extends from the thalamus to the medulla. Its function is to arouse the cerebellum, and includes the projection pathways for a conscious sensory perception.
An alteration in sensorium may be a result of lesions affecting both cerebral hemispheres or a focal lesion affecting the reticular activating system
Define ataxia based on neuroanatomic regions (Where can it originate)
Uncoordinated gait resulting from lesions in the vestibular system, cerebellum or proprioceptive system
Neuroanatomically speaking, why are Trigeminal and facial nerve deficits (Horner’s syndrome) frequently associated with central vestibular disease?
Because of the close association between these nerves and the vestibular nucleus on the rostral medulla
Unilateral prosencephalic lesions Will result in what kind of postural reactions and gait?
Contralateral postural reaction abnormalities with normal gait, possibly accompanied by contralateral menace and sensory deficits
Neuroanatomic localization to a patient displaying a deficiency in the thoracic limb withdrawal flexor reflex
C6-T2 (most likely), but also possibly C1-C5 if segmental reflexes are exaggerated.
Neuroanatomic Localization for a patient with pelvic limb withdrawal flexor reflex deficits
L6-S1 (Sciatic nerve)
What nerve is most likely affected in a patient with a plantigrade stance
Tibial nerve
What nerve is most likely affected in a patient placing the rear foot on its dorsal surface
Common peroneal nerve (Fibular)
Explain the Crossed extension phenomenon and what it might indicate
“In a normal animal that is standing, if one limb is flexed off the ground, the contralateral limb develops increased muscular tone of the extensors to bear more of the patient’s weight and avoid falling. This reaction occurs without volition and is part of a local reflex arc between the left and right limbs. However, in a patient in lateral recumbency, flexion of a limb should not “result in extension of the contralateral limb because the patient is not bearing weight. In lateral recumbency, this reflex extension is inhibited by descending upper motor neuron input. In patients with lesions cranial to the spinal cord segments containing the lower motor neuron units of the limbs, a crossed extensor reflex may be elicited when the withdrawal-flexor reflex is evaluated. Reflex extension may occur in the limb opposite to that being tested, implicating an upper motor neuron lesion on the side where the limb extends. Although this typically is an abnormal reflex indicative of upper motor neuron disease, normal dogs occasionally have crossed extensor reflexes. To avoid voluntary extension of the contralateral limb as a response to the noxious stimulus, the withdrawal-flexor reflex should be elicited with a very mild pinch, and the opposite limb should be observed for extension”
Explain the neuroatomic pathway of the cutaneous trunci reflex
“Regional segmental spinal nerves carry sensory impulses into the spinal cord, where they are relayed cranially to spinal cord segments C8 and T1. At this level, a synapse occurs on the lower motor neurons of both lateral thoracic nerves that innervate the cutaneous trunci muscle. ”
The reflex remains positive1 to 2 vertebral segments caudal to the site of lesion
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
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Explain the “clasp knife effect” and when it is most likely to be encountered
“This reflex is named after the experience of closing the blade of a pocket knife. As the knife blade is folded closed, resistance to closure is appreciated until a point after which the knife blade folds easily. Analogous to closing a pocket knife, in patients with a lesion affecting the upper motor neuron tracts and consequent extensor tone, there is the presence of increased tone that prevents forced flexion of the limb by the examiner until it suddenly gives way to complete flexion without resistance. This reflex is aimed at protecting from overstretch of the muscle. It is mediated through Golgi tendon organs embedded in tendons; when stimulated, there is a reflex inhibition of the muscle.”
More likely to be encountered with upper motor neuron disease
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Three functions of the facial nerve
Motor to the muscles of expression, parasympathetic to the lachrymal glands, sensory to the tongue (taste)
Function of the abducens nerve; signs of dysfunction
Motor to the lateral rectus and retractor bulbi muscles;  medial strabismus
Function of the glossopharyngeal nerve; Typical test and sign of dysfunction
Motor and sensory to the pharynx; gagging reflex; dysphasia
Functions of the vagus nerve, assessment tests (three), signs of dysfunction (four)
Functions: Sensory and motor to the tongue, larynx and viscera
Tests: Gag reflex, oculocardiac reflex, observation of inspiratory stridor
Dysfunction: diminished gag reflects, dysphasia, laryngeal paralysis, megaesophagus
What are the two branches of the accessory nerve and what do they innervate?
External branch is Motor to the trapezius muscle
The internal range joints with cranial nerve X to innervate the larynx
Function of the hypoglossus nerve; Signs of dysfunction
Motor to the tongue. Tongue atrophy, inability to retract to either side
Describe the anatomic pathway of Manace response
“The menace response requires a functional retina, optic nerve, optic tract, lateral geniculate nucleus of the thalamus (diencephalon), and optic radiation and occipital lobe of the cerebrum, as well as the efferent pathway, which includes the facial neurons, nerves, and the muscles for facial expression—specifically the orbicularis muscle for closure of the palpebral fissure.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain the indirect pupillary light reflex
“The indirect pupillary light reflex occurs because most of the optic nerve fibers cross at the optic chiasm, and then most fibers cross back at the level of the pre-tectal nucleus, stimulating the parasympathetic oculomotor nuclei of CN III bilaterally.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Ptosis and mydriasis - Most likely affected nerve, why
Cranial nerve III (Oculomotor); Controls the Levator Palpebral superioris muscle and is parasympathetic to the pupil.
Describe the anatomy of the sympathetic trunk and how it relates to the development of Horner’s syndrome
“For the sympathetic innervation, the preganglionic neurons are distributed in the thoracolumbar spinal cord. Axons from preganglionic neurons synapse in the ganglia of the sympathetic trunk adjacent to the vertebral column. Preganglionic sympathetic neurons destined to innervate the eye are located in the T1 through T3 spinal cord segments. After leaving the vertebral column, axons course through the cranial thoracic cavity, pass through the brachial plexus to join descending fibers “of the vagus, and form the vagosympathetic trunk, which courses in the carotid sheath. These sympathetic fibers course in the carotid sheath to the cranial cervical ganglia. Preganglionic axons synapse in the cranial cervical ganglia located ventromedial to the tympanic bullae. Postganglionic axons enter the cranial cavity; join with axons of the ophthalmic branch of the trigeminal nerve, which exits the cranial cavity via the orbital fissure; and ultimately innervate the dilator muscle of the pupil in the iris. In addition, an upper motor neuron system facilitates the function of the preganglionic sympathetics. This upper motor neuron system begins in the hypothalamus and descends in the lateral funiculus of the spinal cord”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Describe the pathway of the palpebral reflex
“Sensory branches (ophthalmic nerve medially, maxillary nerve laterally) of the trigeminal nerve mediate the afferent arm of the palpebral reflex, and the palpebral branch of the facial nerve mediates the efferent motor arm”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
What is the expected presentation for a patient with unilateral mandibular nerve dysfunction
“With unilateral mandibular nerve dysfunction (e.g., trigeminal nerve sheath neoplasia), no loss of jaw function will be appreciable, but profound muscle atrophy may be present. ”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
What is the expected presentation for a patient with bilateral mandibular nerve dysfunction?
“With bilateral mandibular nerve dysfunction (e.g., idiopathic trigeminal neuritis), the patient may have a “dropped jaw” due to an inability to close the mouth and may drool excessively. ”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
What neurologic presentation can be expected from a patient with a severely contused sciatic nerve? What kind of response can be expected of local stimulation tests and why?
“A patient with a severely contused sciatic nerve typically maintains sensation to the medial aspect of the paw. If the medial surface of the paw is stimulated in a patient with injury only involving the sciatic nerve, the animal will be able to flex the hip joint because of intact innervation of the iliopsoas muscle (innervated by spinal nerve L1 through L4) and the rectus femoris muscle (innervated by the femoral nerve), but the stifle, tarsus, and digits will not flex. Therefore, the medial, dorsal, and plantar surfaces of the pelvic limb paw should be tested for the withdrawal-flexor reflex and for nociception.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
What are the five possible regions of neuroanatomic diagnosis?
Prosencephalon, mid to caudal brainstem (midbrain, pons and medulla oblongata), cerebellum, spinal cord and lower motor neurons
Explain the “two engine gait”
“ambulatory patients with C6-T2 spinal cord lesion typically have a disconnected, “two-engine,” gait, in which the thoracic limbs are “short and choppy” (lower motor neuron quality gait) and pelvic “limbs are long-strided and hypermetric (general proprioceptive ataxia and upper motor neuron paresis).2 If a spinal cord lesion is in the lumbar intumescence, lower motor neuron signs will be present in the pelvic limbs.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Nerve responsible for arytenoid muscle muscle function
Recurrent laryngeal nerve
Minimum specific database for neuromuscular disease (6)
Serum creatinine kinase
Serum electrolytes
Blood or plasma lactate
Urine testing for myoglobinuria
Thyroid hormone screening
Acetylcholine receptor antibody assay
How many ventricles are contained within the central nervous system and where are they located?
“ventricles, of which there are four: one lateral ventricle within each cerebral hemisphere, the third ventricle within the diencephalon, and the fourth ventricle lying ventral to the cerebellum. ”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
What is the function of the mesencephalic aqueduct?
To conduct CSF between the third and fourth ventricles
What two membranes are known as leptomeninges?
Pia matter and arachnoid
What two membranes are known as pachymeninges?
Arachnoid and dura matter
What happens to the Dura matter inside of the skull?
It becomes fused with the periosteum of the skull it is therefore indistinguishable
Which cell produces myelin in the central nervous system?
Oligodendrocytes
What cell line is responsible for the metabolic auto regulation within the central nervous system?
Astrocytes
What factors determine cerebral blood flow?
Mean arterial blood pressure and intracranial pressure
CPP= MABP-ICP
What is the Cushing’s reflex?
“Marked hypotension or elevation in intracranial pressure may reduce cerebral perfusion enough to cause ischemia of neurons in the medulla. This in turn causes a massive increase in systemic vasomotor tone to increase mean arterial blood pressure and therefore cerebral perfusion pressure. The resultant systemic vasoconstriction can be so intense that it is damaging to other organs such as the kidneys. The ensuing systemic hypertension activates baroreceptors, causing a reflex bradycardia (Cushing’s reflex).”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
The percentage effect decrease in intracranial pressure caused by craniotomy versus durotomy
10% vs 65%
Explain the function of the P glycoprotein in the central nervous system
 “Substances not only are excluded from entry to the central nervous system by the blood-brain barrier, but are actively extruded by energy-dependent efflux pumps such as p-glycoprotein.33 Mutations in the gene encoding this protein (the multi-drug-resistance gene—MDR1, now called ABCB1) are a well-known cause of susceptibility to adverse effects of drugs such as ivermectin in Collie breeds.1”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain the phenomenon of central nervous system induced immune depression and its relationship with the indiscriminate use of corticosteroids during central nervous system injury
“Circulating lymphocyte and monocyte numbers are depressed for several days after acute spinal cord injury,133 and lymphocyte function is depressed for several months after both spinal cord injury and stroke.35 This is accompanied by elevations in serum adrenocorticotropic hormone (ACTH) and catecholamines and increased urine cortisol. Conversely, circulating neutrophil numbers increase,133 and the capacity for oxidative bursting, which can be associated with injury to distant organs, is enhanced.65 The term central nervous system injury–induced immunodepression (CIDS) has been coined to refer to the syndrome of immunodeficiency associated with central nervous system injury.105 From the surgeon’s perspective, these pathologic events are important because they highlight the potentially deleterious effects of indiscriminate use of corticosteroids in the treatment of patients with acute central nervous system trauma.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain the sequence of events that follow traumatic injury to the central nervous system and eventually lead to secondary injury
Trauma leads to direct injury to neuronal, axonal in glial cell membranes as well as blood vessels. The decreased perfusion reduces energy supply to neurons and glia cells, causing ion pumps to fail or reverse, subsequently leading to cell membrane damage and increased permeability. Intracellular sodium, chloride and calcium ions increase, upsetting osmotic balance and causing cellular edema. The increase in intracellular calcium and sodium is perpetuated by an increase in extracellular glutamate which, in excess of concentrations, can cause neuron and oligodendrocyte death. This happens because extracellular glutamate concentrations are typically regulated by astrocytes. Mechanical damage to neurons, energetic deficit and impaired uptake by astrocytes leads to an increase in the concentration of glutamate which activates NMDA receptors, leading to an increase in Intracellular calcium. Increased intracellular calcium leads to activation of intracellular proteases such as Calpains and caspase, which destroy the cytoskeleton and initiate apoptosis. Intracellular calcium also activates phospholipase a which initiates the cyclooxygenase pathway and starts the inflammatory response. Finally, intracellular hypercalcemia binds to phosphate in further depletes the cellular energetic metabolism.
Explain at a cellular level the sequence of events that following traumatic injury to the central nervous system
“Traumatic injury to the central nervous system rapidly initiates an inflammatory response within the damaged tissue (which is more pronounced in the spinal cord than in the cerebrum139) and contributes to the secondary injury that develops after the primary impact.124 Upregulation of peptidase matrix metalloproteinase 9 following injury has been identified as an important early trigger to the inflammatory response.114 Microglial cells release the cytokines interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-α), as well as potentially toxic chemicals such as hydrogen peroxide, nitric oxide, and proteinases, within minutes of injury.57 Two phases of cellular infiltration then occur: first, influx of neutrophils, which peaks within a few hours, then influx of macrophages, which reaches a peak at 5 to 7 days.43 This second phase of cellular infiltration coincides with secondary demyelination and loss of axons.16,17 If circulating macrophages are experimentally depleted, the functional outcome is improved, suggesting that they play an important role in tissue damage and functional loss.18,57,125 However, some products of activated phagocytic cells, through production of appropriate growth factors, may aid recovery of tissue integrity and revascularization after tissue damage.94,107 In addition, evidence suggests that inflammation[…]”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
What is the proposed mechanism by which corticosteroids can dramatically improve the neurological presentation of a patient with an intracranial neoplasm?
Reduction of vasogenic edema
Explain the role of oligodendrocytes and glutamate In the context of chronic spinal cord compression
“With more chronic compression, necrosis and apoptosis of glial cells (oligodendrocytes and astrocytes), neurons, and axons may occur.27,51,69,176 In both clinical27 and experimental51 compression, demyelination is a prominent pathologic feature. Oligodendrocytes have high energy requirements to produce and maintain the myelin sheath, and compression may result in ischemia and therefore oligodendrocyte death. Oligodendrocytes are extremely sensitive to the excitotoxic effects of glutamate101 (acting through both AMPA and NMDA channels),92 the concentration of which increases when active astrocytic uptake fails and the action of white matter glutamate transporters is reversed. The concentration of glutamate in cerebrospinal fluid is elevated in dogs with chronic compressive lesions involving the thoracolumbar spinal cord, suggesting that excitotoxicity may play a pathophysiologic role in chronic compression”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain, at a physiologic level, how rapid decompression (surgical) of the spinal cord can lead to dramatic improvement in a patient’s neurological status
Surgical decompression has been linked to a rapid increase in blood flow as well as with relief of the physical deformation of myelin and axons. The improvement in blood flow will restore the much needed nutrient supply to oligodendrocytes, maintaining or repairing myelin production. It will also allow astrocytes to uptake glutamate and reverse vasogenic edema.
What are the two major pathophysiological consequences of hemorrhage within the central nervous system?
Metabolic energy deficit, leading to demyelination due to oligodendrocyte failure and vasogenic edema due to astrocyte failure (inability to uptake glutamate)
Production of free oxygen radicals (as a result of the oxidation of iron and copper from hemoglobin), which damage neuronal, glial and endothelial cells
Which cell line can cross an intact blood brain barrier?
Lymphocytes
Explain the pathology of the blockage of the mesencephalic aqueduct
Blockage of the mesencephalic aqueduct Is one form of congenital malformation which leads to increased pressure within the third and lateral ventricles and secondary (obstructive) hydrocephalus with subsequent cell death
Briefly explain the physiologic mechanism of hepatic encephalopathy
Imbalance of excitatory and inhibitory neurotransmitters, presence of neurotoxins such as ammonia, urea and phosphates
Briefly explain the physiologic basis to uremic encephalopathy
“the presence of neurotoxins such as ammonia, urea, and phosphates (hepatic and uremic encephalopathy), ionic imbalances (uremic encephalopathy), and changes in blood pressure (uremic encephalopathy).”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Most common neoplasms that metastasized to the central nervous system
Hemangiosarcomas, melanomas & carcinomas
Explain the physiology of cytotoxic edema within the central nervous system
“Cytotoxic edema manifests as intracellular swelling in the presence of a normal blood-brain barrier and arises as the result of failure of ion pumps at the cell membrane, allowing excessive entry of sodium “and water. It is commonly associated with ischemia and hypoxia (both of which can occur with contusion, vascular disease, and other diseases that can affect energy balance, such as repeated seizures), metabolic disorders, and intoxication and usually is most pronounced within astrocytes. ”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain the physiologic basis of vasogenic edema within the central nervous system
“Vasogenic edema results from increased vascular permeability and causes accumulation of extracellular fluid, particularly within white matter tracts. It is commonly associated with contusion, inflammatory disease, vascular disease, and compressive diseases such as neoplasia. ”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain the importance in differentiating cytotoxic from vasogenic edema in as much as it affects therapeutic approach to cerebral edema
“Categorizing edema by type allows prediction of the best means of treatment. For instance, cytotoxic edema is best treated by alleviation of the underlying cause, whereas corticosteroids are effective in reducing perilesional vasogenic edema.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain the pathophysiology of Hensen Type I intravertebral disc disease
“Hansen type I degeneration, the nucleus undergoes progressive decrease in proteoglycan content, with consequent dehydration and accumulation of mineral (also known as chondroid degeneration). This degeneration leads to loss of its ability to withstand pressure equally and causes secondary degeneration and “tearing in the annulus fibrosus. Finally, in an acute episode of mechanical stress, the nucleus is expelled through a tear in the annulus (usually termed intervertebral disc extrusion). Because the nucleus is eccentrically placed within the annulus, the expelled nucleus tends to be projected dorsally and to affect the spinal cord. The resultant injury consists of varying degrees of both contusion and compression.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain the pathophysiology of Hensen type II intravertebral disc disease
“Hansen type II degeneration, the nucleus is progressively dehydrated and replaced by fibrinoid tissue, with a consequent increase in stress transfer to the annulus. The annulus then undergoes a “wear-and-tear” degeneration that leads to rupture of fibers over a period of months to years. This allows the nucleus to cause protrusions of the dorsal aspect of the annulus, which compresses the spinal cord”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Clinical signs typically associated with myelomalacia
“distress, subnormal temperatures, and gastrointestinal disturbances.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain the role of astrocytic proliferation and its effects on the response to central nervous system injury
“astrocytic proliferation and hypertrophy (termed astrocytosis or gliosis) commonly evolve to produce a “scar,” which is easily observed on histologic examination. Although this astrocytosis reconstitutes a central nervous system environment, it can have detrimental consequences, for instance, by forming a barrier to regrowth of axons.46 Astrocytosis found at epileptogenic foci could be considered to have proseizure or antiseizure activity, although the balance of opinion appears to suggest that astrocytosis is primarily a response to abnormal activity in the neurons.5,82”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Name three conditions that commonly result in syringomyelia
“diseases that alter cerebrospinal fluid flow (classically causing turbulence), such as arachnoiditis, Chiari-like malformations, and elevated intracranial pressure due to brain neoplasia, can all result in syringomyelia”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Explain, and a basic level, the phenomenon of synaptic plasticity
In response to distruction of afferent input, cells tend to upregulate their number of receptors to a given neurotransmitter leading to “hypersensitivity“ to this substance. The response to the nearest transmitter may also change via changes in the types of ion channels expressed on the surface of the cell (alteration in sodium channel properties of bladder afferents after chronic spinal injury, for example)
The appropriate interarcuate space for cerebrospinal fluid collection in the lumbar region for dogs and cats
Dogs: L5-L6
Cats: L6-L7
Define xanthochromia and what it indicates
“Yellow or straw-tinged cerebrospinal fluid is referred to as xanthochromic, and it suggests previous subarachnoid hemorrhage (in the absence of hyperbilirubinemia). Xanthochromia is caused by an accumulation of blood pigments such as hemoglobin, and it may occur within several hours of an acute hemorrhagic insult (trauma, bleeding disorders, and occasionally severe central nervous system inflammation).”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Discuss the typical signalment and pathophysiology of canine degenerative myelopathy
“Degenerative myelopathy (syn: degenerative radiculomyelopathy) is a neurodegenerative disorder that primarily affects the spinal cord of middle-aged to older dogs, and, rarely, older cats.4,38,91 The disorder is a diffuse axonopathy associated with necrosis primarily in the lateral and ventral funiculi of the thoracolumbar spinal cord segments (Figure 30.2).38 The axonopathy is accompanied by secondary demyelination and astrogliosis. Degenerative myelopathy is overrepresented in the German Shepherd Dog, the Pembroke Welsh Corgi, the Boxer, and the Rhodesian Ridgeback but also has been reported in the Siberian Husky, the Miniature Poodle, and the Chesapeake Bay Retriever. “Neuroanatomic localization in dogs with degenerative myelopathy commonly is consistent with a lesion involving the third thoracic through third lumbar (T3-L3 myelopathy) spinal cord segments, and the disease is typified by a progressive upper motor neuron paresis and general proprioceptive ataxia in the pelvic limbs.3”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Gene mutation associated with degenerative myelopathy and dogs
SOD1
Most common cause of infectious meningomyelitis in dogs
Canine distemper
Most common non-infectious cause of meningomyelitis in dogs
Steroid responsive meningitis-arthritis
Clinical signs and pathophysiology of steroid responsive meningitis arteritis
“Steroid-responsive meningitis-arteritis is a sporadic disorder characterized by episodes of profound cervical hyperesthesia, depression, and pyrexia.38 Clinical signs result from combined meningitis and arteritis of leptomeningeal vessels (Figure 30.3). Arteritis also may involve the vessels of the heart, mediastinum, and thyroid glands.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Bloodwork and CSF abnormalities typical of steroid responsive meningitis/arteritis
Good test to monitor response to treatment
Bloodwork: polymorphonuclear pleocytosis (predominantly neutrophils, occasionally degenerative), hyperglobulinemia
CSF: elevated protein levels, elevated IgA levels
C-Reactive protein
Basic level describe the etiopathogenesis of the protracted form of canine steroid responsive meningitis/arteritis
“A second, more chronic form of steroid-responsive meningitis-arteritis may occur following relapses of acute disease and/or inadequate treatment.137 In this form of disease, meningeal fibrosis secondary to the inflammatory process may obstruct cerebrospinal fluid flow or occlude the vasculature, rarely causing secondary hydrocephalus or ischemia of the central nervous system parenchyma, respectively.126 Involvement of the motor and proprioceptive systems may lead to variable degrees of paresis and ataxia; other neurologic signs, such as a menace deficit, anisocoria, or vestibular signs, may occur with severe disease.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Signalment and Clinical signs typically associated with granulomatous Meningoencephalitis
Female, toy/terrier breeds, approximately five years old
Rapidly progressing multifocal CNS disease, vestibulocerebelar signs, seizures, cervical spine, visual deficits.
What are the three forms of GME
Disseminated, local and ocular
Describe the etiopathogenesis of GME, including all two forms
“Granulomatous meningoencephalomyelitis is an angiocentric, nonsuppurative, mixed lymphoid inflammatory process affecting predominantly the white matter of the cerebrum, caudal brainstem, cervical spinal cord, and meninges (Figure 30.4).17,35 The focal form of granulomatous meningoencephalomyelitis is a true mass lesion resulting from the coalescence of perivascular cellular infiltrates, involving a large number of blood vessels in one region. “The ocular form of granulomatous meningoencephalomyelitis also consists of perivascular cellular infiltrates primarily localized to the retinal or postretinal aspects of the optic nerve and optic chiasm.99,126
”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Is there a gender predisposition in GME?
Yes, females are more commonly affected
What is the currently proposed etiology of GME ?
“granulomatous meningoencephalomyelitis is a nonspecific inflammatory response to various antigens, of which pathogens may constitute an important subset.”
Neurologic phases of canine distemper virus infection
Initial phase - typically asymptomatic non-supportive leptomeningitis and perivascular encephalitis
Gray matter disease - typically one week - dogs may die within 2 to 3 weeks with seizures or progress into white matter disease
White matter disease (most common form) - three weeks post infection, characterized by demyelination with axonal sparing. Dogs typically die within 4 to 5 weeks or recover with minimal central nervous system injury
Necrotizing Meningoencephalitis (approximately 4 to 5 weeks post infection) nonsuppurative inflammation following the demyelination phase. Thought to occur secondary to exuberant inflammatory response to the white matter lesions. Typically combined with chorioretinitis and UTIs. Some dogs may recover while others may die.
Differential diagnosis for canine distemper virus – suspected cases ( with neurological abnormalities)
Congenital anomalies (decompensating hydrocephalus, Chiari like malformations)
AA subluxation
trauma
neurotoxins (mycotoxins)
Metabolic disease
What are the two most common presentations associated with toxoplasma and neospora infections in dogs?
Meningoencephalitis (Multifocal neurologic signs; Unique cerebellar presentation caused by Neospora reported in dogs)
Myositis-polyradiculoneuritis: juvenile dogs younger than six months of age, myositis, progressive radiculoneuritis, pronounced muscle atrophy
Etiopathogenesis Of canine and feline toxoplasmosis
“Transmission of T. gondii to dogs and cats most commonly occurs secondary to carnivorous ingestion of encysted bradyzoites or tachyzoites, but sporozoites and tachyzoites also may be transmitted orofecally and transplacentally.42 The cat is the definitive host for T. gondii and excretes oocysts in its feces. Oocysts sporulate and may infect other mammals in 1 to 5 days. All mammals, including cats, may become intermediate hosts upon ingestion of sporulated oocysts. Multiple organ infection, including ocular, central nervous system, pulmonary, liver, and skeletal muscle involvement, may occur concurrently in intermediate hosts. Focal and/or diffuse infiltration of lymphocytes, plasma cells, and histiocytes may be present in the meninges and neuroparenchyma of the central nervous system.”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Definitive host and mode of transmission of toxoplasma
Cats, fecal oral transmission. Oocysts become infected in feces within 1 to 5 days. Cats typically become infected through consumption of infected meat. Contact with oocyts in fecal material leads to infection as an intermediate host, which can occur to cats, dogs humans and many other species
Definitive host and presumed mode of transmission of Neospora
Dogs, presumably fecal oral. Vertical transmission is also very likely given the multiple dogs in a litter are frequently affected
Bacterial agents reportedly associated with canine and feline meningitis
“PESANK”
Pasteurella spp., Escherichia coli, Staphylococcus spp., Actinomyces spp., Nocardia spp., Klebsiella spp.”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Most common sources of infection in cases of bacterial meningitis and epidural empyema
Must select antibiotics to cross the blood brain barrier
Hematogenous spread (urinary tract infection)
direct inoculation from traumatic wounds or needles (CSF tap)
direct extension from structures of the head (eyes, ears, nasal cavity via cribriform plate)
Paraspinal absences, migrating foreign bodies, tail fractures or infections in cats
Antibiotic therapy for bacterial meningitis/epidural empyema.
Antibiotic choice should ideally be based on culture and sensitivity. Whether based on culture or empirically, must administer intravenous for the first three days to reach adequate blood levels more rapidly. Followed with three months of oral treatment. Options include metronidazole, fluoroquinolones, chloramphenicol and trimethoprim sulfa
Third generation cephalosporins like ceftiofur (IM) and cefpodoxime (orally)
Typical Signalment for dogs with discospondylitis
Large breed, male, middle-age. Breeds include great Dane, Rottweilers, labrador retriever, German Shepherd and English bulldog.
The percentage of cases according to one study in which the causative agent of discospondylitis was identified on a combination of blood in urine culture
40%
Burkett, BA et al, JAVMA 2005
Zoonotic agent frequently associated with canine discospondylitis
Brucella canis
Dog breed frequently affected by fungal discospondylitis
German Shepherd
Fibrocartilagenous embolism is most commonly a disease of large breed dogs, including German Shepherd, Staffordshire terrier, Labrador retriever And boxers. Which of these small breed dogs is also frequently affected by this condition?
Schnauzer
In 2007, De Risio et al. Describe an association between the initial neurologic score and the presence and extent of MRI abnormalities. Briefly describe the scoring system they proposed for prognostication of patients with FCE
 “Objective measurement of the ischemic lesion included a ratio of the length of the ischemic lesion to the length of the C6 or T2 vertebral body (lesion-to-length ratio). In addition, the maximal cross-sectional area of the hyperintense lesion on T2-weighted images was evaluated as a percentage of total cross-sectional area of the spinal cord. The presence of MRI abnormalities was not significantly associated with the timing of imaging but was associated with ambulatory status on presentation. Severity of signs on presentation was associated with extent of the lesion on MRI. “Affected dogs recover voluntary motor activity, regain unassisted ambulation, and achieve maximal recovery at 6 days (range, 2.5 to 15 days), 11 days (range, 4 to 136 days), and 3.75 months (range, 1 to 12 months), respectively.39 Unsuccessful (euthanized, severe proprioceptive and motor deficits, urinary or fecal incontinence) recoveries occurred when the MRI lesion-to-vertebral length ratio was ≥ 2, and successful (clinically normal or mild general proprioceptive/motor deficits) when the ratio was ≤ 2. With lesion-to-vertebral length ratios ≥ 2 and ≤ 2, 60% had an unsuccessful outcome and 100% had a successful outcome, respectively. MRI therefore may be helpful in predicting outcome in dogs with fibrocartilaginous embolic myelopathy.
”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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A large breed dog is presented for paresis affecting the thoracic limbs (bilaterally symmetrical), but the pelvic limbs appear only mildly affected. Name of the syndrome and localized lesion
Central spinal cord syndrome, affecting the white matter deep in the spinal cord
A patient presents with severe motor dysfunction affecting the thoracic limbs come out though the signs are moderately asymmetrical. The neurologic evaluation of the pelvic limbs is completely normal. Where is the lesion?
Lower motor neuron affecting the brachial plexus or peripheral nerve roots of C6-T2 (non-spinal).
The most clinically useful and objective reflexes in the thoracic limbs
Flexor withdrawal reflexes
Describe the neuroanatomic pathway of the panniculus reflex
The panniculus muscle extends from the lower cervical region approximately the level of the sixth lumbar vertebra it is innervated by the lateral thoracic nerve which originates at C8-T1. Testing is based on pinching or breaking the skin starting at the level of the wings of the ileum in progress in cranially reflects will stop approximately two segments caudal to the site of lesion
What is the neuroanatomic Rationale to explain the fact that dogs typically develop pelvic limp neurologic deficits before thoracic limb deficits in cases of compressive spinal disease?
The motor tracts innervating the pelvic limbs are located more peripherally in the spinal cord, and are thereby more prone to external trauma
Fecal incontinence of a upper motor neuron origin is more commonly associated with what kind of lesion?
Cystic lesions affecting the dorsal aspect of the spinal cord (more commonly caudal to T2) may cause disruption of the sensory pathways for defecation. Reflex defecation/urination remain intact
Describe the modified ventral approach to the cervical vertebral column
“A modified ventral approach to the cervical vertebral column via a paramedian dissection also has been described.31 After identification of the sternocephalicus and sternohyoideus muscles, the right sternocephalicus muscle is separated from the right sternohyoideus muscle (Figure 31.3). The sternohyoideus muscles are then retracted to the left with the trachea, esophagus, and carotid sheath. Further exposure of the vertebrae after this point is as for the standard approach. This approach helps protect the trachea, right recurrent laryngeal nerve, and the contents of the right carotid sheath (the vagosympathetic trunk, carotid artery, and internal jugular vein), while providing increased exposure of the caudal cervical vertebrae after elevation of the longus colli and longus capital muscles and decreasing the likelihood of hemorrhage from the right caudal thyroid artery.31”
During the ventral approach to the cervical vertebra column we will encounter the carotid sheath. What is contained within the structure?
The vagosympathetic trunk, common carotid artery and internal jugular vein
What are the two structures frequently associated with complications during the standard ventral approach to the cranial cervical vertebral column?
The cranial thyroid artery and the recurrent laryngeal nerve
Describe the lateral approach to the cervical vertebral column
Palpate the articular processes of C3 to C6
Perform a curvilinear incision from C2 to the cranial margin of the scapula
Incise the platysma muscle to expose the brachycephalic and the trapezius muscles.
In the cranial cervical region the splenius and the Serratur ventralis are exposed by blindly dividing and retracting the brachycephalicus muscle (grid technique)
Superficial fibers of the Serratus ventralis I bluntly divided and retracted exposing the longissimus system
Describe the basic lateral approach to the brachial plexus
Perform a long curvilinear incision 3 to 4 cm cranially from the midpoint of the cranial border of the scapula to appoint located slightly distal to the greater tubercle of the humerus
Incise the platysma muscle and the fascia cervicalis exposing the cleidocervicalis, omotransversarius and the trapezius muscles.
Ligate the superficial cervical artery and vein as they emerge between the cleidocervicalis and the trapezius muscles. Retract the superficial cervical lymph node, which lies medial to these vessels, caudally.
Incise the omotransversarius muscle near its insertion of the distal end of the spine of the scapula and retract cranially
Continue dissection mediately to the deep fascia along the border of the cleidocervicalis muscle. Place a Gelpi retractor between this muscle and the trapezius.
Retract the scapula caudally with a Farabeuf retractor to expose the nerves of the plexus
What are the three branches of the common carotid artery at the level of the first cervical vertebra?
Internal carotid, external carotid and occipital arteries
Typical Signalment for dogs with atlantoaxial subluxation
Young small breed dogs such as Yorkshire terriers, Chihuahuas, Pomeranians and Pekingese. Less frequently reported in large breed dogs but overrepresented in the standard poodle
Radiographic abnormality typical encountered in patients with atlantoaxial subluxation
Increased distance between the dorsal lamina of the atlas and the spinous process of the axis
Name the four most common dorsal techniques utilized to stabilize atlantoaxial instability
Dorsal atlantoaxial wiring
Nuchal Ligament technique
Dorsal cross pinning
Kishigami Atlantoaxial tension band
What are the 13 nerves that compose the brachial plexus in the dog?
“brachiocephalic, suprascapular, subscapular, axillary, musculocutaneous, radial, median, ulnar, dorsal thoracic, lateral thoracic, long thoracic, pectoral, and muscular branches.146”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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What is the most common anatomic location for brachial plexus injuries and why?
The dorsal root, immediately as it emerges from the spinal cord (intradural). Spinal nerves lack an epi-neuron at this site, making them more vulnerable to traction
What are the five classes of nerve injuries? Briefly explain
Grade 1 - neurapraxia (Interruption of function and conduction without structural change). Recovery is likely
Grade 2 - Axonotmesis (damage to axon is severe enough that Walerian degeneration of the distal portion of the nerve follows. Internal architecture is preserved including in the neuron and Schwann sheath). Recovery as possible but may take a few weeks
Grade 3 - Neurotmesis (disruption of axons and endoneuron but for secular orientation is preserved by an intact perineurium.).
Grade 4 - Neurotmesis (disruption of the Perineurium)
Grade 5 - Neurotmesis (The entire nerve is severed)
Injuries to the brachial plexus are typically divided into cranial (rare) and caudal (common) lesions. What nerves are involved in cranial lesions and what kind of disabilities can be expected?
C6-C7
Musculocutaneous, axillary, subscapular and suprascapular nerves
The extensor muscles of the elbow are not affected, so the animal can bear weight on the affected limb. There is loss of shoulder movement and elbow joint flexion, and atrophy of the supraspinatus and infraspinatus muscles usually develop overtime
Injuries to the caudal portion of the brachial plexus Are more common than cranial injuries. What nerves are typically affected, in what spinal segments do they originate and what clinical signs can be expected?
Radial nerve, median nerve and ulnar nerve
C8-T2
The limb may be carried in a flexed position because the nerves that control elbow And shoulder flexion (musculocutaneous, axillary and suprascapular nerves) remain intact. The patient is unable to bear weight on the limb due to inability to extend of the elbow and the carpus since the necessary muscles are innervated by the radial nerve (Involved in 92% of cases)
A large percentage of patients with brachial plexus injuries also present with ipsilateral Horner’s syndrome. Explain the pathoanatomy of this phenomenon
The preganglionic fibers that innervate the eye originate at T1. Injury to these fibers will lead to sympathetic denervation, leading to myosis/ptosis/exposure of the nictitating membrane
A large percentage of patients with brachioplexus injury also present with loss of the panniculus reflects on the ipsilateral side. Explain this phenomenon
The panniculus muscle is innervated by the lateral thoracic nerve which originates from spinal segments C8-T1 Injury to those segments is common with caudal brachial plexus injuries
What can be expected with an injury involving all of the nerves composed in the brachial plexus (extending from C6 to T2)
The patient will most likely present with complete paralysis of the limb (dragging). The shoulder will be carried lower than the contralateral side. The limb is likely to be completely analgesic distal to the elbow but sensory routes can sometimes be spared
A patient is presented with severe injury to the brachial plexus. You request an MRI and observe a focal area of hypointesity on the spinal cord in the C8 -T1 spinal cord segment region(T2-weighed sagital image). What does this image most likely indicate?
Hemosiderin deposition secondary to hemorrhage
Define the term neurotization
The re-innervation of a denervated motor or sensory end organ
Discuss the most likely prognosis for a dog or cat diagnosed with a complete avulsion of the radial nerve
Patients affected by a complete avulsion of the radial nerve are expected to have a guarded to poor prognosis. all patients must be given a 4–6 weeks before a grave prognosis is pronounced. Options may include carpal arthrodesis (if able to extend the elbow, although quite rare) or more likely amputation.
Typical Signalment and presentation of extradural synovial cyst
Middle-age to older large and giant breed dogs. Most commonly observed in the lumbosacral junction, frequently in combination with degenerative lumbosacral stenosis. The cysts typically arise from the zygapophyseal joints, likely as a response to degeneration. Best diagnosed via MRI (hyperintense on T2-weighed images)
Correct nomenclature for the sinovial joints formed by the articular processes that arise from the pedicles of the vertebrae
zygapophyseal joint.
Explain the difference between a Funkquist A, Funkquist B and a Modified Dorsal Laminectomy
“Funkquist A involves removing the spinous process, laminae, articular processes, and approximately half of the dorsal portion of the pedicles of a vertebra to gain access to the vertebral canal. It provides maximum exposure of the vertebral canal.84 Funkquist B leaves the articular processes and pedicles intact but removes the spinous process and laminae. A modified dorsal laminectomy is midway between Funkquist A and Funkquist B. For the modified dorsal laminectomy, the laminae, spinous process, and caudal articular processes are removed. The medial aspect(s) of the pedicles is undercut to enhance exposure, but the cranial articular processes remain intact ”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Alpha adrenergic antagonists useful as pharmacological intervention targeted at relaxing the internal urethral sphincter in cases of UMN bladder
Phenoxybenzamine and prazosin
Describe the Griffiths Modified 5-point grading scale for neurologic disfunction
Griffiths Modified 5-Point scale
0: normal
1: Pain, not severe enough to result in neurologic disfunction
2: Paresis with or without pain; the degree of paresis or proprioceptive deficits become worse as disease becomes more severe
3: Plegia; total loss of voluntary movement in the affected limbs (and/or tail)
4: Plegia with loss of voluntary urinary function
5: Plegia with loss of voluntary urinary function AND loss of nociception in the affected limb (and /or tail)
Reported diagnostic accuracy of myelogram in cases of IVDE (Type I IVDD) and how/when it compares to CT/MRI
Reported diagnostic accuracy 70 to 99%, but less accurate than CT or MRI for lateralize lesions.
Reported incidence of post-myelographic seizures
20%
How does non-contrast CT compare to myelography in the diagnosis of IVDE in chondrodystrophic breeds?
Non-contrast CT is as diagnostic as myelography for IVDE in chondrodystrophic breeds, but the work-up must be completed with CT-myelogram or MRI if no lesions are found that explain the patient’s neurologic exam findings. More sensitive than conventional myelography for lateralized lesions.
Main advantages and disadvantages of MRI in comparison to radiographs, myelography and CT
- Best soft tissue contrast among available imaging techniques (lowest risk of false-negative results as compared to previous techniques).
- Allows obtention of images in multiple planes without repositioning the patient.
- Myelography is not necessary (in contrast with CT) since tissue contrast can be manipulated with different acquisition sequences.
- Requires general anesthesia;
- Study takes significantly more time that CT;
- MRI devices are more expensive and require more maintenance.
What is the key prognostic determinant in cases of IVDE. Percentages.
Presence of nociception (“deep pain”) at the time of diagnosis. 80 to 95% of dogs with preserved nociception recover motor function within 2 weeks of surgery, as compared to 50% for those without preserved nociception. The previous notion that dogs who lost nociception for longer than 48 hours have a grave prognosis for return of normal function appears to be erroneous according to more recent reports. These dogs appear to have a similar prognosis top those who lost nociception within less than 48 hours. Only presence or absence of nociception has been consistently associated with better or worse prognosis.
MRI appearance of the intervertebral disk in cases of herniation
“Intervertebral disc material is typically hypointense on T1-weighted (T1W) and T2-weighted (T2W) images, although in some instances animals may extrude nondegenerate nucleus pulposus (particularly common in the cervical vertebral column), which appears isointense on T1W images and hyperintense on T2W images.2”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Define Spina Bifida and list the two most common meningeal and meningospinal issues associated with this condition
What breed of cats and what kind of dogs are predisposed?
“Failure of the laminae to fuse dorsally is referred to as spina bifida and is often associated with concomitant neural tube malformation, especially meningocele (meninges herniated through the bony defect) or meningomyelocele (meninges and spinal cord herniated through the bony defect).268”
Minx cats and screw tail dogs are predisposed
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Define pilonidal sinus (dermoid sinus) - embryonic cause, clinical presentation, predisposed breed
“Pilonidal sinus (dermoid sinus) refers to a congenital condition wherein the skin fails to completely separate from the neural tube during embryonic development.12,67 Phenotypically, the defect is a focal tubular structure (sinus) with a cutaneous opening lined by squamous epithelium and occasionally hair follicles.6 The sinus penetrates deeper tissues and in some cases reaches the level of the dura mater. The defect is found on the dorsal midline in dogs, with most cases reported in the cervicothoracic or sacrococcygeal regions.118,182 The presence of a pilonidal or dermoid sinus has been reported in cases of spina bifida as well”
Rhodesian Ridgeback
“Clinical features are dependent on the location of the sinus and the degree of tissue penetration. Infection of the sinus may lead to myelitis or meningitis. Pain and neurologic dysfunction may occur secondary to inflammation or as a result of the tethering effect the sinus has on the spinal cord or nerve roots”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Discuss the embryonic origin of epidermoid cysts, typical clinical presentation and histologic features.
“Incomplete separation of the neuroectoderm from ectodermal tissue can entrap viable ectodermal cells within the central nervous system, leading to a condition termed epidermoid cyst (cholesteatoma). The cyst is lined by keratinizing stratified squamous epithelium.102,178,221,265 Epidermoid cysts most commonly form at or near midline during closure of the neural tube.241 Growth of the cyst occurs via accumulation of keratinocytes, keratinaceous material, and cholesterol. Affected animals are usually normal at birth but develop signs as the cyst enlarges and compresses adjacent neural tissue. Clinical signs reflect the anatomic level involved.39,241 Epidermoid cysts have been reported intracranially (within the caudal cranial fossa) and less commonly within the spinal cord.h The condition is thought to be congenital; however, an acquired cyst may develop secondary to implantation of epithelial cells after repeated cerebrospinal fluid collection in young dogs.154 Histopathologic evaluation of tissue from the cyst is the only way to confirm the diagnosis. Theoretically, complete removal of the tissue can be curative; however, few reports of successful treatment exist in the veterinary literature.37”
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Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Briefly discuss subarachnoid “cysts”, potential presentation, predisposed breeds and therapy
“Subarachnoid diverticula are defined as focal accumulations of cerebrospinal fluid within the arachnoid membrane or subarachnoid space.67,94 This fluid-filled area tends to form over the dorsal or dorsolateral aspect of the spinal cord, with very few reports of ventral diverticula. The structures have no epithelial lining; therefore, technically, they are not a true cyst and instead have been referred to as a “pseudocysts.”93 Pseudonyms for this condition include arachnoid pseudocyst, meningeal or leptomeningeal cyst, and arachnoid cyst.”
“Clinical features include a protracted progressive history of general proprioceptive ataxia and upper motor neuron paresis and also incontinence.11,261 Any breed or age can be affected, but younger adult (<18 months) Pugs and Rottweilers represent the most commonly reported breeds, and males tend to be predisposed”
“The lesion may be approached by dorsal laminectomy or hemilaminectomy, and the laminectomy should be large enough to allow complete access to the diverticulum on the basis of preoperative imaging. The diverticulum may be fenestrated or marsupialized. Although relatively few cases of subarachnoid diverticula are reported in the literature, a trend toward better outcomes is seen if the incised dura is marsupialized by suturing it to the surrounding fascia. Surgical removal of the diverticulum may allow spinal cord decompression; however, re-formation of the lesion is a reported complication.261 Those cases that are younger in age and have had a shorter duration of clinical signs may have a better prognosis.261”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Briefly discuss myelodysplasia. Most commonly affected breed, typical clinical presentation
“Myelodysplasia is a congenital malformation of the spinal cord most commonly reported in Weimaraner dogs.44 Incomplete or abnormal fusion of the neural tube along the sagittal plane leads to neurologic dysfunction. Clinical features that strongly suggest myelodysplasia include early onset (1 to 2 months of age) of a nonpainful T3-L3 myelopathy. One consistent feature of affected dogs is the use of both pelvic limbs simultaneously to propel themselves forward (bunny-hopping). Decreased proprioception of the pelvic limbs is also common. Results of myelography and CT are typically normal because the lesion is microscopic. Magnetic resonance imaging has not been well evaluated. In suspected cases, testing is performed to rule out other diseases that mimic this condition. No treatment is known; however, affected dogs do no not appear to be in pain, and signs are rarely progressive.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Roughly what percentage of paraplegic dogs Who lost nociception recover the ability to walk if the condition was a result of intravertebral disc disease versus spinal trauma
40 to 70% for IVDD
12% for traumatic spinal injury
What is the recommended initial approach to a patient with severe spinal trauma?
 Basic assessment for concomitant thoracic, abdominal and cerebral injury
Very brief neurological assessment to determine the presence or absence of nociception
Immediate stabilization of the entire body using straps or tape against a rigid platform (a board). The head should also be stabilized if cervical trauma suspected. Light sedation/analgesia should be used as needed
What is the most common tumor of the central nervous system observed in young dogs and young cats?
Extrarenal nephroblastoma (dogs)
Lymphoma (cats)
Most common location for spinal cord neoplasm in dogs? Most common location within the vertebral canal
Cervical region; extradural (50%)
List the most common early and late adverse effects observed after radiation therapy utilized to treat CNS neoplasia.
“Adverse effects of radiation are classified as early (acute) or late (chronic).61,106 Early effects occur in proliferating tissues such as epithelium and bone marrow.”
Late adverse effects involve nonproliferating tissues such as nervous tissue, vascular tissue, and bone. These effects occur 6 months to years after radiation therapy63,165 and include white matter necrosis; atrophy, hemorrhage, or infarction of nervous tissues; chronic progressive myelitis due to vascular injury; and fibrosis/gliosis”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Define myokymia, most common cause and treatment
“Myokymia, involuntary muscle contractions resulting in vermiform (rippling) movements of the overlying skin and muscle cramping, may occur as a late side effect to radiation.149 Regular periodic injections of botulinum toxin into the affected muscle can control the clinical signs.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Define the role of Samarium 153 in cancer therapy - most common use, reported response rate
“Samarium-153 EDTMP (Samarium-153 lexidronam, Sm-153) is an injectable radioisotope that concentrates in areas of osteoblastic activity. This drug has been used for palliation of pain due to osteosarcoma and metastatic bone neoplasms in “dogs. Response rates for osteosarcoma were 60% to 80% for 3 months. Side effects primarily involve myelosuppression.
”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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At what locations should rhizotomies performed as part of tumor excision be avoided as much as possible? Why?
Cervical and lumbar intumescence. Major nerves arise from these locations (i.e. radial nerve, owner nerve, femoral nerve, etc.), and the rhizotomy (excision of a nerve route) may result in significant disability.
What are the most common intramedullary spinal tumors in dogs?
“Primary neoplasms include neoplasms arising from ependyma, glia (astrocytoma, oligodendroglioma, undifferentiated glial neoplasms), other neuroectodermal precursors, or stromal origins (primary sarcoma).82,83,130,137,153 In dogs, the two most common intramedullary primary neoplasms are ependymoma and astrocytoma.122,130,171,192,196 However, in one report, primary sarcoma of the spinal cord accounted for approximately 50% ”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Describe the swallowing mechanism including the involved muscles. Explain the pathophysiology of cricopharyngeal achalasia.
“In normal swallowing, food is grasped by the teeth and formed into a bolus by rapid tongue movements. The bolus is pushed up and back by the base of the tongue into the oropharynx. The hypopharyngeal, pterygopharyngeal, and palatopharyngeal muscles contract and force the bolus through the relaxed upper esophageal sphincter (cricopharyngeal, thyropharyngeal muscles) into the cervical portion of the esophagus. The cricopharyngeal muscle contracts after the bolus passes. Cricopharyngeal muscle tone is linked to deglutition and the respiratory cycle. During swallowing, the airways are protected by the soft palate (which closes the nasopharynx) and the epiglottis (which flips back to close the glottis).
“Cricopharyngeal achalasia is characterized by inadequate relaxation of the cricopharyngeal muscle and/or lack of coordination with pharyngeal muscle contractions during swallowing. This disrupts the cricopharyngeal phase of swallowing, causing food to remain in the pharynx and produce gagging, regurgitation, aspiration, and coughing.”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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What is the typical Signalment of a patient affected by cricopharyngeal achalasia? How can it be differentiated from pharyngeal dysphasia?
Rare condition, typically affecting springer or cocker spaniels as well as miniature poodles. Clinical signs are typically noticed at the beginning of eating solid food. Gagging, retching, expulsion of saliva covered food are typical. Regurgitation occurs immediately after swallowing. Most patients have a voracious appetite but eventually become anorexic and lose weight.
Pharyngeal dysphasia is caused by inadequate pharyngeal contraction and typically affects older dogs. May also be associated with esophageal hypomotility and megaesophagus.
What are the medical and surgical treatment options for cricopharyngeal achalasia? What are the risks?
Medical treatment: intralesional injection of botulinum toxin. Improving therapeutic modalities
Surgical treatment: cricopharyngeal myectomy. Typically curative, but potentially disastrous if misdiagnosed (affected by other pharyngeal dysphasias)
Name the two most important spinal cord pain projection pathways
“Of most clinical importance in terms of conscious perception and reaction to noxious stimuli are the spinothalamic and spinocervicothalamic tract.”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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Describe the pathophysiology of neurogenic inflammation, including the name of at least 5 inflammatory mediators.
“Local inflammatory mediators in peripheral tissue are responsible for creating the signal that will ultimately be perceived as pain. Such mediators released by tissue after injury include bradykinin, prostaglandins, leukotrienes, serotonin, arachidonic acid, histamine, nerve growth factor, tumor necrosis factor, substance P, acetylcholine, adenosine triphosphate, and protons. Many of these inflammatory mediators and cytokines are released from epithelial cells, endothelial cells, mast cells, macrophages, and platelets. Prostaglandin E2 (PGE2) is an arachidonic acid metabolite generated by cyclooxygenase (COX) released from damaged cells. Bradykinin is a potent pain-producing peptide; it directly activates Aδ and C fibers and increases the synthesis and release of prostaglandins by nearby cells.2,7–10 If unabated, stimulation of peripheral nociceptors by these mediators can lead to release of additional inflammatory mediators by the nociceptors themselves, leading to amplification of the local inflammation via a process of neurogenic inflammation”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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Describe the pathophysiology of peripheral sensitization
“If unabated, stimulation of peripheral nociceptors by these mediators can lead to release of additional inflammatory mediators by the nociceptors themselves, leading to amplification of the local inflammation via a process of neurogenic inflammation. In addition to cytokines already mentioned, nociceptors may release other chemicals such as substance P and calcitonin gene-related peptide. Both these peptides can cause increased tissue edema by direct actions on venules. They also activate local mast cells, leading to histamine release; histamine accentuates the pain response by decreasing the threshold for nociceptor activation. These processes can ultimately lead to peripheral sensitization, a phenomenon in which nociceptor afferent neurons become hyperexcitable to stimuli, effectively increasing the gain of the response of these peripheral neurons to potentially noxious stimuli”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What is the role of histamine in the pathophysiology of peripheral sensitization?
“histamine accentuates the pain response by decreasing the threshold for nociceptor activation.”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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What is the primary role of Glutamate? What nerve fibers typically release this neurotransmitter?
“Glutamate is the predominant excitatory neurotransmitter released by Aδ and C fibers in the spinal cord gray matter. ”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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Discuss some of the mechanisms that lead to central sensitization
“Wind-up via excessive glutamate activation of neuronal NMDA receptors.• Release of normal inhibition of NMDA receptor overstimulation via co-release of substance P and CGRP from hyperstimulated C-fibers (see earlier). This involves Mg++ channels.• Transcriptional and translational changes in postsynaptic dorsal horn neurons (pain “memory”).• Activation of central nervous system microglial cells (by substance P, glutamate, etc.), which upregulate cyclooxygenase-2, and release other neuroactive substances (which increase excitability of dorsal horn neurons).• Axonal sprouting, altered neuronal connectivity and cell death; all associated with microglial cell activation.”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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Explain the “Gate control theory”
“In addition to mechanisms within the peripheral nervous system (PNS) and CNS that serve to exacerbate painful states, there are a number of segmental (spinal cord) and suprasegmental (brain) modulatory systems within the CNS that act to ameliorate the sensation of pain. At the spinal cord level, some interneurons of the dorsal gray column are inhibitory to projection neurons that provide the majority of axons for the various pain-transmitting spinal cord pathways. These interneurons can be stimulated by fast-conducting, nonnociceptive myelinated Aβ fibers (normally convey touch, pressure, and some proprioceptive sensation) as well as by a subset of nonnociceptive Aδ fibers. When stimulated, these fibers can, via excitation of the inhibitory interneuron, prohibit firing of the slower conducting C fibers. In other words, by the time the nociceptive stimulus carried by the C fiber arrives at the dorsal horn, an inhibitory interneuron that has been excited by a faster conducting myelinated fiber has already been given the signal to prohibit C fiber stimulation of dorsal horn projection neurons. This is the basis of the gate control theory. In essence, the faster conducting nonnociceptive fibers “close the gate” to slower conducting nociceptive fibers. The inhibitory interneurons involved in[…]”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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Nerves and associated spinal segments tested during withdrawal reflex assessment of the pelvic limbs
Sciatic nerve ( L6-S1)
Femoral nerve (L4-L6)
Ventral motor branches to the psoas major muscle group for hip flexion
Nerves and spinal segment “range” tested by the withdrawal reflex on the forelimb
“In the thoracic limb, the dorsal thoracic, axillary, musculocutaneous, median, ulnar, and radial nerves are responsible for flexion of the shoulder, elbow, carpus, and digits. The nerves responsible for this reflex arise from spinal cord segments C6-T2.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
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Describe the Modified Frankel grading system for spinal cord injury
Grade 0: para- or tetraplegia with no deep nociception
Grade 1: para- or tetraplegia with no superficial nociception
Grade 2: para- or tetraplegia with nociception
Grade 3: non ambulatory para- or tetraparesis
Grade 4: ambulatory para- or tetraparesis with GP ataxia
Grade 5: spinal hyperesthesia only
Most common myelopathy to affect Schnauzers
FCE
List some of the features of FCP and HNPE that can be used to differentiate the two conditions
• English Staffordshire bull terriers are prone to FCE, whereas border collies are prone to HNPE.
• HNPE dogs are more likely to vocalize at onset of signs, compared with FCE dogs.
• HNPE dogs are more likely to have C1–C5 lesions than FCE dogs.
• HNPE dogs are more likely to exhibit spinal hyperesthesia on initial examination than FCE dogs
• HNPE dogs are more likely to be ambulatory at time of hospital discharge than FCE dogs.
• FCE dogs are more likely to have L4–S3 lesions (and long-term fecal incontinence) than HNPE dogs.
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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What are the four most common peripheral neuropathies encountered in domestic animals?
myasthenia gravis (MG)
autoimmune polymyositis
polyradiculoneuritis
tick paralysis.”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What is the pathophysiology of acquired myasthenia gravis?
“Acquired MG is an autoimmune disorder of the neuromuscular junction in which autoantibodies are formed against nicotinic acetylcholine (ACh) receptors of skeletal muscle. ”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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Megaesophagus is it common consequence of acquired myasthenia gravis. Why does it happen?
“Megaesophagus is a frequent feature of acquired MG in dogs because of the high proportion of skeletal muscle in the canine esophagus; ”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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At what ages is acquired myasthenia gravis most commonly observed? What are the most commonly affected canine and feline breeds?
“There is a bimodal age distribution for acquired MG in both dogs and cats, with peak incidences at approximately 3 and 10 years of age. Both males and females are affected, although there may be a slight decreased tendency for sexually intact dogs to develop MG. Breeds most commonly afflicted with MG include German shepherds, golden retrievers, and Labrador retrievers. Other breeds with a relatively high risk for MG include Akitas, terriers, and German shorthaired pointers. Somali cats (related to Abyssinians) and Abyssinian cats are at risk for developing acquired MG.”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What is the most common clinical sign associated with acquired by asthenia gravis in dogs and cats? What is the diagnostic implication of this?
“Dogs and cats with MG typically do not have specific neurologic deficits but display varying levels of weakness. It is common for pelvic limb weakness to be the main (sometimes the only) clinical manifestation in dogs with MG; this feature often leads to misdiagnosis of MG as either a myelopathy or pelvic limb musculoskeletal disorder.”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What are the three forms of acquired myasthenia gravis? What are the typical clinical features of each form?
Focal MG: Clinical Signs of Appendicular (Limb) Muscle Weakness. Can present as megaesophagus, pharyngeal weakness, laryngeal weakness, and/or facial muscle weakness: each of these may be the sole presentation or may occur in any combination
Generalized MG: Clinical Signs of Appendicular Weakness. Typically see most (or all) of weakness in pelvic limbs, but thoracic limbs can be involved
Acute Fulminating MG: Rapid Onset and Progression of Severe Weakness. Profound focal and appendicular weakness. Acute onset, rapid progression to nonambulatory tetraparesis and respiratory distress. Usually fatal”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What is the most common cause of acquired myasthenia gravis in cats?
“Mediastinal masses (typically thymoma) are much more common in cats with acquired MG than in myasthenic dogs; in one retrospective study of 235 cats with acquired MG, 52% had evidence of a mediastinal mass (vs. 3.4% in dogs).1”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What are the diagnostic tests that can be used to diagnose myasthenia gravis? How specific is each test?
“The most definitive blood test for the diagnosis of acquired MG is an immunoprecipitation radioimmunoassay that quantitates serum autoantibodies directed against the ACh receptor. Concentrations of ACh receptor antibody above 0.6 nM/L and 0.3 nM/L are diagnostic for MG in dogs and cats, respectively. The edrophonium (Tensilon) challenge test may provide a presumptive diagnosis of MG in patients while awaiting results of an radioimmunoassay if it is clearly positive (i.e., the patient displays a clear improvement in strength shortly after administration of IV edrophonium). However, some dogs with various myopathies will also display increased strength after receiving edrophonium. Although the association between MG and thyroid disease is tenuous, thyroid status should be evaluated in MG patients.”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What are the medical treatment options for canine and feline acquired myasthenia gravis? Include drugs and nursing care
Anticholinesterase Drugs
Pyridostigmine (preferred anticholinesterase drug)
Neostigmine (only if pyridostigmine is not available)
Immunosuppressive Drugs
Azathioprine (dogs)
Cyclosporine
Mycophenolate mofetil (dogs)
Thymectomy
Thymic hyperplasia (not evaluated in dogs and cats)
Thymoma (not until MG signs controlled)
Hormonal Therapy
Thyroxine if dog is hypothyroid
Nutritional Support
Elevated feedings
Gastrostomy tube feedings
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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The treatment of acquired myasthenia gravis typically involves the use of Anticholinesterase drugs and immunosuppressive therapy. What is the preferred Anticholinesterase? What immune suppressant drug should be avoided and why?
“Medical management of acquired MG in dogs and cats is typically either oral pyridostigmine or oral pyridostigmine plus immunosuppressive therapy (see Box 30.14). Treatment options for canine and feline MG are summarized in Box 44.2. Prednisolone often causes an initial worsening of weakness in dogs with MG; this adverse effect is potentially severe enough to justify avoiding prednisolone as an immunosuppressive agent for canine MG. A similar adverse effect of prednisolone treatment has not been documented for cats with acquired MG.”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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When assessing mental status one must describe both quality and content. What are the 4 levels of mentation? Describe clinics features of each and most likely location of lesion
Alert - conscious, responsive (normal)
Obtunded - depressed, listless and disoriented. Easily aroused with minor stimulus (“out of it”). Lesion: Forebrain
Stuporous - unconscious but can be aroused with a strong stimulus. I lesion: usually brainstem or diffuse forebrain.
Comatose - unconscious and not aroused even with strong stimulus. Lesion: brainstem or diffuse forebrain
What 3 cranial nerves are tested by the corneal reflex?
V,VI and VII
Trigeminal nerve (V, ophthalmic branch) - afferent pathway
Abducens (VI) - efferent, motor to retractor bulbi muscle
Facial (VII) - efferent, motor to palpebral muscles (blink reflex)
How is the facial nerve clinically evaluated ?
Blink reflex
Corneal reflex
Trigeminofacial reflex (stimulate maxillary region/medial canthus and observe blink)
Stimulate inner pinna and observe behavioral response
Define Attitude and Posture as they pertain to the neurologic evaluation
Attitude - position of the eyes and head in relation to the body
Posture - position of the body respect to gravity
Patient ambulating with wide, side-to-side head excursions. Type of ataxia? Location?
Bilateral vestibular
Peripheral vestibular apparatus
Describe and explain the phenomenon of abdominal breathing in the context of cervical spinal disease
“Caudal cervical spinal cord lesions that spare innervation to the phrenic nerve LMNs (e.g., lesions caudal to the C5–C7 segments) but disrupt normal activation of intercostal LMNs can lead to the phenomenon of abdominal breathing. In this scenario, the diaphragm bears the sole burden of moving air through the lungs because of the denervated chest wall, and this motion causes the abdomen to visibly move back and forth during respiration”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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Explain why cervical myelopathies may be associated with severe hypotension
“Tonic input to the sympathetic LMNs in the thoracolumbar spinal cord that maintain normal blood pressure is provided by neurons in the medulla (rostroventrolateral medulla). Because these medullary neurons send their processes through the cervical spinal cord, cervical myelopathies may be associated with severe hypotension.”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What are the distinctive anatomic features of C1 which can be used for identification during dorsal or ventral approach to the cervical vertebral column?
“The first cervical vertebra (C1), the atlas, has a shortened body (the ventral arch); wide, shelf-like transverse processes (wings); and modified articular processes. The ventral tubercle of C1 feels like a distinctive “spike” when palpated during a ventral approach (Fig. 40.2), compared with the smooth “bump” of the ventral aspect of the intervertebral disc spaces. ”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What important anatomical consideration must be made when evaluating the possibility of intravertebral disc disease affecting the C1 - C2 location?
“No intervertebral disc is found between the first and second cervical vertebrae.”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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Discuss the important anatomical considerations between second, third and fourth cervical vertebrae during the dorsal surgical approach to the area
“The dorsal spinous process of C2 (the axis) is a distinctive bladelike structure, the caudal aspect of which is very thick and partially overhangs the dorsal aspect of C3. The dorsal spinous process of C3 is extremely small and is sometimes nonapparent, especially in miniature and toy dog breeds. The dorsal lamina of C3 in these small breeds may be very short as well. It is important not to confuse C4 with C3 while performing a dorsal approach in the cranial cervical spine, especially in small dogs and cats.”
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Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
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What are the important anatomical landmarks to be palpated during the ventral approach to the caudal cervical spine? what precaution must be taken when palpating one of these landmarks?
“The transverse processes of C6 are very prominent ventral structures that are easily palpated during the ventral approach. The dorsal aspect of the first rib as it articulates with T1 can also be palpated during the ventral approach; however, the surgeon must be cautious not to rupture the thin cupula pleura during palpation of this structure.”
Excerpt From
Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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What are the two most common immediate complications of a ventral slot or dorsal laminectomy performed in cervical region? What are the approximate complication rates?
“The most common complications are transient neurologic worsening after surgery and venous sinus hemorrhage (which may require transfusion)”
“In a large (546 cases) retrospective study of dogs with cervical disc extrusions treated via ventral slot surgery, acute adverse events were documented in approximately 10% of the patients. These adverse events were considered to be major in 6.4% of cases (deterioration in neurologic status, persistent pain, intraoperative hemorrhage), and roughly half of this group required reoperation. Adverse events in this study were associated with NSAID administration, less experienced surgeons, C7–T1 extrusions, and intraoperative hypotension”
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Small Animal Surgery E-Book
Theresa Welch Fossum DVM, MS, PhD, Dipl ACVS
https://books.apple.com/us/book/small-animal-surgery-e-book/id1367916984
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Brachial Plexus Injury - Difference between Neuropraxia, Axonotmesis and Neurotmesis
○ Neurapraxia: transient conduction block to the nerves without anatomic interruption (avulsion)
○ Axonotmesis: partial avulsion of brachial plexus nerves (disruption of the axon; endoneurium, perineurium, epineurium remain intact)
○ Neurotmesis: complete avulsion of brachial plexus nerves (axon and surrounding connective tissue)
Brachial plexus injury, neuritis or neoplasia may be associated with loss of ipsilateral cutaneous trunci reflex and Horner’s syndrome. Justify the neuroanatomic basis for these concomitant neurologic abnormalities?
○ Loss of ipsilateral cutaneous trunci reflex
■ Lateral thoracic nerve injury (C8-T1 spinal nerve roots)
○ Ipsilateral Horner’s syndrome
■ Sympathetic pathway (T1-T3 spinal nerve roots)
Most common clinical findings compatible with Brachial Plexus Avulsion
Lameness or paresis with hypotonia and hyporeflexia of the thoracic limbs, +/− ipsilateral Horner’s syndrome, +/− loss of ipsilateral cutaneous trunci, and normal pelvic limbs
Name 6 differential diagnosis for a patient with clinical signs of Brachial Plexus Avulsion
- Neoplasia: soft-tissue sarcoma, lymphoma
• Intervertebral disc disease (lateralized)
• Musculoskeletal injury: fracture, joint dislocation, muscle avulsion
• Neuropathy: rabies encephalomyelitis, acute canine polyradiculoneuritis/coonhound paralysis
There are three most common causes of Brachial Plexus disfunction.. What are they and what are their prognosis?
• Trauma (Brachial plexus injury)
○ Preservation of deep pain sensation warrants a fair to good prognosis for return to function over weeks to months.
○ Loss of deep pain sensation suggests an avulsion and warrants a grave prognosis for return to function.
○ Lack of any neurologic improvement over a 4-6 week period suggests permanent injury.
• Brachial plexus neuritis carries a guarded prognosis, but recovery has been reported.
• Overall prognosis is poor for malignant nerve sheath tumors that are not surgically resectable.
What are the three most important points to be observed during the acute treatment of patients with Brachial Plexus Injury?
• Supportive care/monitoring/resuscitation for traumatic injuries
• Prevent self-mutilation or trauma to the affected limbs:
○ Booties to protect the paw
○ Elizabethan collar to prevent licking and chewing
○ Neuropathic analgesia
■ Gabapentin (10 mg/kg PO q 8h): may prevent paresthesia and self-mutilation
• Glucocorticoids: might be of benefit for brachial plexus neuritis, although sufficient scientific information to support their use has not been confirmed.
What are the three most important points to be observed during the chronic treatment of patients with Brachial Plexus Injury?
• Prevent self-mutilation
• Physical rehabilitation: maintain joint mobility and prevent muscle contracture
○ Target all joints of the affected limbs
○ Passive-range-of-motion (PROM) exercises for 10-15 minutes 3-5 times daily
• Limb amputation may be indicated in cases with
○ Permanent unilateral brachial plexus avulsion (no improvement after 6 weeks)
○ Documented or highly suspect malignant nerve sheath neoplasia
• Radiation therapy can be considered for cases of brachial plexus tumors
• Limb-sparing treatments (e.g., nerve root transplantation, transposition, neurotization, muscle transposition) for brachial plexus avulsions are often unrewarding with limited reports of recovery of neurologic function in the affected limb.
What is the minimum amount of time a patient should be conservatively treated for Brachial Plexus injury before amputation can be considered?
6 weeks
The facial nerve provides motor innervation to the muscles of expression, but produces a small sensory branch in dogs and cats. What area does this branch innervate? How can it be easily tested during a CN assessment?
Small sensory branch to the inner concave aspect of the pinna.
D. Cutaneous sensory testing
1. Autonomous zone of facial nerve (dog and cat)
Fold over the pinna. Touch or gently pinch the inner surface of the pinna in the area of the fold. Observe for the ipsilateral eye to blink, ear movement and a conscious response (turning head, growling, etc).
CN VII afferent, CN VII efferent, cerebral cortex
UMN tracts responsible for communication between the Pontine Micturition Center and the Pelvic Nerves
SRT
spinothalamic tract
Reticulothalamic tract
Tectospinal tract
Normal ICP range for dogs and cats
5 to 12 mmHg
Three structures that contrast-enhance in the brain on a T1-weighed contrast-enhanced MRI
Choroid plexus
Pituitary gland
CN-V
What are the three long ligaments that support the vertebral column?
Supraspinous ligament
Dorsal longitudinal ligament
Ventral, longitudinal ligament
What are the three short ligaments that support the vertebral column?
Interspinous ligament.
Intertransverse ligament
Yellow ligaments
The intercapital ligament is present between which spinal segments?
T2-T11
Describe the sequence of tissues encountered during a dorsal approach to the thoracolumbar spinal cord
Skin
Subcutaneous
Thoracolumbar fascia
Multifidus musculature > transect tendons of attachment to the zygapophyseal joints
Longissimus lumborum musculature > transect tendon of attachment to the accessory process > Spinal root and vessels located immediately ventral and cranial to these tendons
Define the Funkquist A technique and how much exposure it affords
“Funkquist A involves removing the spinous process, laminae, articular processes, and approximately half of the dorsal portion of the pedicles of a vertebra to gain access to the vertebral canal. It provides maximum exposure of the vertebral canal”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Define the Funkquist B technique and how much exposure it affords
“Funkquist B leaves the articular processes and pedicles intact but removes the spinous process and laminae”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Describe the Modified Dorsal Laminectomy and how it compares to Funkquist A and B
“A modified dorsal laminectomy is midway between Funkquist A and Funkquist B. For the modified dorsal laminectomy, the laminae, spinous process, and caudal articular processes are removed. The medial aspect(s) of the pedicles is undercut to enhance exposure, but the cranial articular processes remain intact”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Concerning MRI usage for the diagnosis of IVDD, define STIR and its purpose
Short Tau Inversion Recovery (STIR)
Suppresses signal from epidural fat to enhance the contrast of extruded or protruded disc material
Concerning MRI for diagnosis of IVDD, define FLAIR
Fluid-attenuated Inversion Recovery (FLAIR)
Attenuates CSF signal to highlight extruded or protruded disc material
List three reasons why cerebral spinal fluid collection should be performed in a case of suspected intervertebral disc disease based on imaging
1) Imaging abnormalities do not necessarily indicate clinical disease (i.e. L7-S1 disk protrusion common in asymptomatic large breed dogs)
2) Diffuse spinal cord compression can be the result of hemorrhage, neoplasia, or empyema.
3) Subarachnoid administration of iodinated contrast can worsen the clinical status of patients with parenchyma spinal cord disease
Define Cholesteatoma
“Incomplete separation of the neuroectoderm from ectodermal tissue can entrap viable ectodermal cells within the central nervous system, leading to a condition termed epidermoid cyst (cholesteatoma). ”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
Define Pilonidal sinus
“Pilonidal sinus (dermoid sinus) refers to a congenital condition wherein the skin fails to completely separate from the neural tube during embryonic development.”
Excerpt From
Veterinary Surgery: Small Animal Expert Consult
Spencer A. Johnston VMD, DACVS & Karen M. Tobias DVM, MS, DACVS
https://books.apple.com/us/book/veterinary-surgery-small-animal-expert-consult/id1250368401
This material may be protected by copyright.
What is the most common causative agent for discospondylitis?
Coagulase positive staphylococci like staphylococcus aureus or intermedius
What is the typical antibiotic choice for discospondylitis? How long is the condition usually treated?
Cephalexin, six weeks
Why is the patellar reflects increased in lumbosacral disease? What is the name of this phenomenon?
Pseudohyperreflexia: Loss of sciatic nerve tone, leading to exaggerated femoral nerve response (quadriceps)
