Neuro Flashcards
What are the 3 types of ataxia?
Vestibular = inner ear, CNVIII periheral (often CN 7 and horners), vestibular nuclei rostral medullar oblongata - central (often CP def, islat CN5&7 def)
proprioceptive (lesion at or caudal to midbrain, usually spinal)
cerebellar = hypermetria
What is decerbrate rigidity?
opisthotonus + rigidity extension 4 limbs =midbrain/rostarl cerebellar lesion
What is decebellate ridgitiy?
opisthotonus + rigidity extension 4 limbs with hip flexed = cerebellum
What is pleurothotonus?
head and neck deviated to one side - mid rostral brainstem, cerebral lesions
What spinal tracts are associated with the general proprioceptive pathway and UMN pathway?
General: spinocerebellar tracts (unconcisous proprioception), fasciculatus gracillus and cuneatus (CP HL and FL)
UMN pathway: reticulospinal and rubrospinal
What is the modified Frankel score?
What spinal segments are associated with the femoral n?
L4-L6
How do you grade the patellar reflex?
0 = absent
1= hypo
2= normal
3= hyper
4= clonic
What nerves to the biceps and triceps reflex test?
Biceps = musculocutaneous (C6-C8)
Triceps = radial = (C7-T2)
What nerves are responisble for withdrawal in the forelimb and hind limb?
Forelimb = dorsal thoracic, axillary, musculocutaneous, median, ulnar and radial (C6-T2)
HL = sciatic (L6-S1)
Where is the cutaneious trunci reflex relayed to?
C8-T1
What does the cross extensor test indicate?
UMN lesion on the opposite side tested
Opposite side extends during withdrawl
What are the cranial n?
1= oflactory 2 = optic, 3 = occulomotor 4= trochlear 5=trigeminal 6= abducens 7= fascial 8= auditory/vestibulocochlear 9= glossophyngeal 10= vagus 11= spinal/accesory 12= hypoglossal
on old olympus towering top a finn and German veiwed some hops
Some say marry money but my brother says big busniess make money
What CN do menace, pupillary light and palpebral test?
menace = CN 2 and 7
pupillary reflex = CN 2 and 3 (also palpebral fissure)
palpebral = CN 5 and 7
What is the pathway of the menace reflex?
CN2, optic tract, lateral genicular nucleus (thalmus/diencephalon), occiptal lobe cerebrum, cerebeullum and facial.
When can evidence of Horner’s syndrome be seen (aka what are possible areas of damage to the sympathetic tracts)?
T1-T3
C1-C5
bracial plexsus
otitis media/interna - sympathetic fibers in petrous portion of the temporal bone
What are signs of CN 3 dysfunction?
Ventrolateral strabismus; ptosis; dilated pupils; diminished to absent PLRs
Normally: Motor to extraocular muscles; parasympathetic to pupil
Test with physiologic nystagmus and PLR
What are signs of dysfucntion of CN 4?
Dorsomedial strabismus (cat); lateral deviation of retinal vein (dog)
Normal: Motor to dorsal oblique muscle
Test: Resting eyeball position (cat); fundic examination (dog)
What are signs of CN 5 dysfunction?
Masticatory muscle atrophy; dropped jaw if bilateral; decreased or absent facial/nasal sensation
Normal: Motor to muscles of mastication (mandibular); sensory to face (ophthalmic, maxillary, mandibular)
Test: Jaw tone; muscle bulk; sensation to face, cornea, and nasal mucosa
What are signs of CN 6 dysfunction?
Medial strabismus
Normal = Motor to lateral rectus and retractor bulbi
Test = Physiologic nystagmus; resting eyeball position
What is CN 7 responisble for besides facial movement?
Motor to muscles of facial expression; parasympathetic to lacrimal glands; sensory (taste) to rostral tongue
Test: Menace response; palpebral reflex; lip retraction; ear movement; Schirmer tear test
What does CN 10 do?
Sensory and motor to pharynx, larynx, and viscera
Test with Gag reflex or oculocardiac reflex
Diminished gag reflex; dysphagia; laryngeal paralysis; megaesophagus
CN 9 is also associated with gag reflex and dysphagia
What does the accessory n do?
Motor to trapezius
Test: Evaluation of muscle mass
Dysfunctional = Atrophy of trapezius
Describe the pathway for vestibular nystagmus?
CN8 → brainstem → vestibular nuclei → medial longitudinal fasciculus → abducens and oculomotor
What nerves are associatied with the palpebral reflex?
CN5 - opthalmic br (medial palpebral), maxiallary branch lateral palpebral
CN7 (palpberal br)
To evaluate mandibular br = evaluate symmetry of masseter and temporalis mm.
What does testing nasal sensation evaluate?
ipsilateral opthalmic and maxillary n innervate masal mucosa = ipsilateral trigeminal lesion
nociceptive pathway = contralateral prosencephalic lesion
Signs assoicated with proencephalon disease
Seizures; abnormal behavior; propulsive activity; depression to coma
Head turn, normal gait; propulsive circling (usually ipsilateral to lesion) or pacing; aimless wandering; head pressing; movement disorders (rare)
Postural Reactions = Contralateral deficits
Cutaneous Sensation = Contralateral (often facial/nasal) hypalgesia
Cranial Nerves = Contralateral menace deficits with normal (optic radiation and occipital cortex) or abnormal (optic chiasm, optic tracts) PLRs; facial; tongue or pharyngeal weakness (rare)
Other = Abnormalities in thirst, appetite, thermoregulation, endocrine dysfunction
Neurologic Signs That May Be Associated With Mid to Caudal Brainstem Disease
Table • 26-4 Neurologic Signs That May Be Associated With Cerebellar Disease
How does Shiff fherrington posture occur?
Disrtuption asending inhibitory axons arising from interneurons (border cells) in the dorsal border of the grey colunm of spinal seg L1 - L4
What is spinal shock?
T3-L3 lesion with LMN signs to hind limbs
What are signs associated with LMN disease?
What comprizes the lower motor neuron unit?
nerve cell body in ventral grey matter CNS
ventral nerve root
peripheral n
muscle/disease effecting neuromuscular transmission mediated by acetylcholine
What tests can be used to differentiate between junctionpathies, neuropathies and mypoathies?
creatinine kinase, aminotrasferase (AST), tensilon test, Ach receptor antibody titer, EMG, and nerve/muscle biopsies
What are differentials for diffuse/multifocal neurologic disease?
disorders myelin formation
diffuse meningitis (shaker syndrome, GME, infectious)
metabolic
dengenerative disease (lysosomal storage disease)
intoxications (mold, algae, ethylene glycol)
What are the essential components of a motor unit?
- motoneuron = cell body (located within the central nervous system, either in the cranial nerve nuclei of the brainstem or in the ventral horns of gray matter in the spinal cord) and its peripheral axon, supported by Schwann cells.
- Neuromuscular junctions.
- Myofibers innervated by the motoneuron.
What are 3 syndromes associated with neuromuscular disorders and their CS?
- Myopathic syndrome = weakness, stiff gait, tremors, atrophy or hypertrophy, muscle pain
- Motor neuropathic syndrome (classic LMN)= flaccid paralysis/esis, neurogenic atrophy, decreased reflexes, fasiculations
- Sensory neuropathic syndrome = hypalgesia/hypesthesia (decreased pain and sensation), CP deficits, decreased reflexes without muscle atrophy
List tests to diagnosis neuromuscular disorders
blood: CK, lytes, lactate, myoglobinuria (aka ammonium sulfate precipitation test), thyroid acthylcholine recptor antibody
Electomyography = peripheral n. conduction
Muscle biopsy
Nerve biopsy
Diagram of the major components of the motor unit (1 through 7) and reflex arc. A, Sensory nerve fiber. B, Dorsal root ganglion. C, Dorsal nerve root. 1, Motor neuron. 2, Ventral nerve root. 3, Spinal nerve. 4, Plexus. 5, Motor nerve fiber. 6, Neuromuscular junctions. 7, Muscle fiber
Table • 27-1 Pathoanatomic Classification of Neuromuscular Disorders
What are types of electrodiagnostic testing?
Electromyography
Nerve conduction velocity testing (motor and sensory)
Somatosensory evoked potentials (cord dorsum potentials)
Late wave analysis (F-wave and H-reflex)
Repetitive nerve stimulation
Single-fiber electromyography
Muscle and nerve biopsy
How do you diagnose masticatory myopathy?
can be made with a positive 2M-antibody titer
Can electromyography ID disorders restricted to sensory neurons?
No
What are normal and abnormal spontaneous activty on EMG?
Normal = insertional activity, miniature end-plate potential (needle positioned in proximity to NM junction), End plate spikes (complete depolarization, motor unit action potential (normal m. not completely at rest).
Abnormal = Fibs and sharps (firing single myofibers due to destablization sarcolemmal membrane), complex repetitive discharges (group of fibers firing in synchrony due to denervation), myotonic potential (congenital myotonia)
Figure 27-2 Electromyography. A, Normal baseline (“electrical silence”). B, Miniature end-plate potentials with a single end-plate spike. C, Fibrillation potentials. D, Positive sharp waves. E, Positive sharp waves and fibrillation potentials. F, Complex repetitive discharges. (Calibration: Amplitude is represented by the vertical line: 100 µV in D, and 50 µV in all other tracings. Time base is represented by the horizontal line: 10 msec in all tracings.)
Peroneal motor nerve conduction study in a normal dog (B) and a dog with a sensorimotor polyneuropathy (C), following stimulation of the peroneal nerve at the hock, stifle, and hip. Compound motor unit action potentials (M-waves) were recorded from the extensor digitalis brevis lateralis muscle (recording electrode). A, Diagram of electrode placement. B, Normal canine peroneal motor nerve conduction study. Note that latency of the M-wave increases with greater distance between stimulating and recording electrodes. Motor nerve conduction velocities calculated in this 1-year-old dog were 69 m/sec (hip to stifle) and 57 m/sec (stifle to hock). C, Abnormal canine peroneal motor nerve conduction study. Note the polyphasia, temporal dispersion, and decrease in amplitude of the M-wave when compared with B. Motor nerve conduction velocities calculated in this 6-year-old dog were slowed: 39 m/sec (hip to stifle) and 32 m/sec (stifle to hock). These abnormalities are consistent with demyelination.
Somatosensory evoked potential study in a normal dog (B) and a dog with a sensorimotor polyneuropathy (C), following stimulation of the peroneal nerve at the level of the fourth distal metatarsus (stimulus site). Somatosensory evoked potentials were recorded from the hock, stifle, hip, and L4-5 (cord dorsum potential [CDP]). Latency measurements for sensory conduction velocity determinations are represented by T1, T2, T3, and T4. A, Diagram of electrode placement. B, Normal canine somatosensory evoked potential study. Although the somatosensory evoked potentials appear to be of similar amplitude at each recording site, the sensitivity increases from hock to L4-5. Note that 1000 individual potentials (N = 1000 to right of figure) were averaged to produce these tracings. C, Abnormal canine somatosensory evoked potential study. All sensory nerve action potentials are severely reduced in amplitude, and sensory nerve conduction velocities are slowed. Dispersion of the potentials is difficult to evaluate, as potentials are barely distinguishable from background noise. Note that compared with (B), 4000 individual potentials (N = 4000) were averaged in an attempt to minimize random background noise from the time-locked electrical signal. These abnormalities are consistent with a severe sensory neuropathy.
Diagrams showing the generation of late waves after stimulation of a mixed nerve and recording from the motor point of a muscle. A, M-wave. B, F-wave. C, H-reflex.
How do you do an EMG?
most frequently used technique for electromyography involves the use of a concentric needle electrode. The central wire of the electrode (active or exploring electrode) is insulated from the surrounding cannula (reference electrode) so that the actual area being tested (between the two) is very small. A ground electrode is used to minimize extraneous “noise.”
Normal canine M-waves (left) and F-waves (right) recorded following peroneal nerve stimulation at the hock (32 superimposed individual tracings). B, Normal canine M-waves (left) and F-waves (right) recorded following peroneal nerve stimulation at the hip (32 superimposed individual tracings). Note the longer latency of the M-waves (left) and the reduced latency of the F-waves (right) when compared with (A). C, Normal canine H-waves recorded following peroneal nerve stimulation at the hip, using a low stimulus intensity (0.6 mA). Note that M-waves are not present (left). D, The same stimulation and recording sites as used in (C), after a slight increase in stimulus intensity (to 1.0 mA). M-waves now are present (left).
Repetitive nerve stimulation. A, Normal canine repetitive nerve stimulation following 1 Hz stimulation of the peroneal nerve at the hock. Note in the data table that M-wave amplitude (Peak Amp mV), area under the M-wave (Area mVms), and percentage amplitude decrement (Amp Decr %) remain constant with consecutive stimuli. B, Decremental response in a cat following 3 Hz peroneal nerve stimulation at the hock. Note that amplitude and area under the M-wave decrease with consecutive stimuli, which is measured as a percentage amplitude decrement of 17% to 44%. The cat had muscular dystrophy. C, Facilitation in a dog following 30 Hz peroneal nerve stimulation at the hock. Note that both area and amplitude of the M-wave are increased (i.e., the M-wave becomes taller and is not narrower). The increase in amplitude is represented by a negative Amp Decr %. A cause could not be determined in this dog presenting with exercise-induced weakness that occurred in warm weather. D, Pseudofacilitation in a normal dog following 30 Hz peroneal nerve stimulation at the hock. Note the increase in amplitude with no change in the area under the curve (i.e., the M-wave becomes taller and narrower). As in (C), the increase in amplitude is represented by a negative Amp Decr %.
What are the physiologic tests to evaluate the NM junction?
- Repetative nerve stimulation - repeated supramaximal while recording M waves
- Single-fiber electromyography - end plate in NM junction = v. sens for aquired myasthenia gravis
What are criteria for selection for muscle biopsy?
- Affected
- minimal approch/morbidity
- Ideally fibers oriented in 1 direction
- Previously described characteristics: latear head triceps (distal 1/3), vastus lateralus (distal 1/3), cr. tibial (prox 1/3), temporalis
- Away from tendon of insertion or aponeuroses
- Free of artifact
What are criteria for selection of nerves for biopsy?
- affected by disease, if diffuse established normal and innervates routine m. biopsy
aka: common peroneal, tibial, ulnar = all contain motor, sensory and autonomic - For sensory = cutaneous sensory n (cd cutaneous antebrachial or cd cutaneous sural)
- Nerve root biopsy
- CN biopsy - facial or trigeminal
What are the techniques for nerve biopsy?
Fascicular
full thickness
How does tissue contrast differ between T1 and T2 weighted images (short vs. long)?
T1 = short T1 relaxtion (hyperintense) - fat, long T1 relaxation (hypointense) = CSF
T2 = short T2 relaxation (hypointese) - muscle, long T2 relaxation (hyperintense) = CSF
Schematic illustrating the two basic pulse sequences, spin echo and gradient echo, and their variations. BOLD, Blood oxygenation level dependent; FIESTA, fast imaging employing steady state acquisition; FLAIR, fluid attenuation inversion recovery; FLASH, fast low-angle shot; fMRI, function magnetic resonance imaging; GRE, gradient echo; HASTE, half Fourier acquisition single-shot turbo spin echo; PDW, proton density weighted; SE, spin echo; SPGR, spoiled gradient recalled; SSFP, steady state free precession; SSFSE, single-shot fast spin echo; STIR, short-tau inversion recovery; T1W, T1-weighted; T2W, T2-weighted; true FISP, true fast imaging with steady state precession.
Substances With High Signal Intensity on T1W and T2W Images
What is the dose of water soluable iodinated contrast and gadolinium?
Water-soluble iodinated contrast medium is usually administered intravenously at a dosage of 400 to 800 mg iodine/kg
Gadolinium: intravenously at a dosage of 0.1 mmol/kg body weight = paramagnetic (enhances/strengthens the magentic field)
What is the Larmor frequency?
Spin at frequrecy porportional to the strength of the magnetic enviroment
Hounsfield Unit Measurements for Various Substances
What is the dose of contrast agents for the spine on CT?
Nonionic contrast media of choice are iohexol (Omnipaque, 240 mgI/mL) and iopamidol (Isovue, 200 mgI/mL), which are administered at dosage of 0.45 mL/kg (full spine) and 0.3 mL/kg (regional): using a cervical or lumbar puncture technique
What is the path of flow of spinal fluid?
CSF (blood ultrafiltrate) formed in Choroid plexus (lateral ventricles) → foramina 3rd ventricle → mesenchepahlic aquaduct → 4th ventricle → lateral apertures from 4th ventricle → subarachnoid space → central canal of spinal cord
What are the 3 meniginges?
pia mater
arachnoid mater
dura mater
Anatomy of spinal cord
3 meniges: dura mater (outide side), arachnoid mater, pia matter (inside)
2 spaces = subarachnoid = CSF, subdural = vessels
epidural = between bone and dura mater = fused with periosteum skull
What is in the grey mater and white matter?
Grey = neuronal cell bodies
White = axons and glial cells
Spinal cord grey on inside (outside in brain and majority of brainstem) = divides white matter into compartments (funiculi)
What is the falx cerebri?
falx cerebri = separates 2 hemispheres (connective tissue)
tentorium cerebelli = separates cerebrum from cerebellum (connective tissue)
What is the resting cell membrane potential for neurons?
Negative 80mV
Action potential = rapid depolarization by influx of Na+ through voltage gated ion channels
Iniated at axon hillock (junction between axon and neuronal cell body
all or nothing
Repolarizes by clsoure of Na channels and eflux of K through open potassium channels
Active extrusion Na in exchange for K and by K uptake by astrocytes
What is produced by oligodendrocytes?
Myelin
What is pressure autoregulation?
pressure sensative smooth m. cells maintain constant P in CNS as long as systemic BP between 50-160mmHg
Affected by intracranial disease
Graph of autoregulatory control of cerebral blood flow (CBF) and vascular diameter, in response to changes in mean arterial pressure (MAP), arterial partial pressure of oxygen (PO2), and arterial partial pressure of carbon dioxide (PCO2).
Profusion highly responsive to arterial paCO2 (as CO2 increase, profusion increase)
1mmHg change PaC02 = 5% change profusion
Intercranial disease = hypoventilation = vasodilation = increase ICP = herniation
Markedly increased profusion if PaO2 <50mmHg
What is the definition of cerebral perfusion pressure?
mean arterial pressure - intracranial pressure
How does low BP or high ICP affect cerebral profusion?
Both cause decreased cerebral perfusion pressure → ischemia in medulla → increased vasomotor tone → increase MAP → increased cerebral profusion
Hypertenion systemic → barorecptors → bradycardia
What is brain - heart syndrome?
If cerebral pressure continues to drop → increase catecholamines → myocardial ischemia → arrythmias
What is normal ICP?
8-15mmHg
ICP >15-20mmHg → abnormal, should be treated
>30mmHg significant decrease in perfusion
Durotomy decrease ICP 65% vs craniotomy alone = 15%
List drugs based on if they are good or poor at crossing the blood brain barrer.
Good = 3rd gen cephal, fluroquin, metronidazole, sulfas, chloramphenicol, trimethoprim
Mod = tetracycline, erythomycin, penicilins, rifampin
Poor = 1st and 2nd gen cepha, aminoglycocides, clindamycin, vancomyacin
What potion of the CNS is not immunologically privlaged?
meninges and choroid plexus = no BBB = normal response to inflammation (ie increased neutrophils and mononuclear cells)
What are the 2 areas in the brain where constitutive neurogenesis occurs in the adult nervous system (ie stem cells)?
subventricular zone/olfactory system
dentate gyrus of the hippocampus
What are the primary and secondary mechanisms of injury related to contusion?
1 = mechanical - swelling, hypoxia, axonal injury
2 = trauma and ischemic
- hemorrhage → decreased perfusion/energy → increase cell permability to Na, Cl, Ca
- damage → increased glutamate →increased Ca and Na uptake (via NMDA, AMPA< kainate receptors)
- increase Ca = apoptosis and activates phopholipase = increased inflammation
- increased mitochondrial permiability →free radicals → vascular damage, edema and vasospasm via increased Trpm4 and parenchyma pressure
What do micoglial (inflammatory cells) release in response to inflammation?
IL-1, TNF alpa, hydrogen peroxide, NO, proteinases
What does compression induce in the brain?
demyelination, edema, axonal degeneration and neuronal necrosis
- via physical deformation myelin (reversible) , vasogenic edema, increase glutamate = demylination via oligodendrocyte damage
Increased intracellular calcium concentration does the following: (3)
- Activates intracellular proteases such as calpains and caspase, which destroy the cytoskeleton and chromosomes and initiate programmed cell death
- Activates phospholipase A2, thereby producing eicosanoids and initiating an inflammatory response
- Binds intracellular phosphates, further depleting the cell of energy sources
What is the max amount of CSF that can be collected?
1ml per 5kg
What are the 2 locations for a CSF tap and what are the landmarks?
- Cerebellomedullary cistern: full flex skull to 90 degree with cervical spine. Intersection lines between occiptal protuberence - C2 and line along cr aspect of aspect of the wings of C2. Keep needle perpendicular to dorsal lamina.
- Lumbar cistern: Legs flexed, L5-L6 dogs, L6-L7 cats
What is considered pleocytosis for CSF (cloudy CSF)? What is a normal cell count CSF?
>500 x 10^6 WBC/L
normal = 0-5 x 10^6 WBC/L
What is a normal protein count for CSF?
<250mg/L (25mg/dL) for cerebromedullary cistern
<450mg/L (45mg/dL) for lumbar cistern
What are common serologic tests for neuro disease?
Toxo, neospora, ehrlichia, rickettsia, coccidiodies
Can do IgG index = CSF IgG/serum IgG, if low it has migrated across BBB,high then CSF is source
What is the histopathologic characteristic of DM
Necrosis primarily in lateral and ventral funiculi of TL spine
Breeds: GSD, Welsh Corgi, Boxer, Rhodesian Ridgeback
Genetic risk factor = mutation in SOD1 gene
Where do the inflammatory lesions occur for steroid responsive meninditits-artertitis (SRMA)?
Leptomeninges and associated a. - etiology unknown
Breeds: Beagle, Boxer, Berner, Weimies, NS duck trolling retrievers
Usually 6-18m range upto 7yr
What are the 3 forms of GME?
disseminated - most common
Focal - slowly progressive, suggestive of mass lesion
Ocular - pupils often fixed or dilated, optice n. swelling, chorioretinitis
What is the treatment for toxoplasma?
Clindamycin 10-25mg/kg BID 3-4 weeks
or
TMS 15mg/kg BID with pyrimethamine 1mg/kg SID
For discospondylitis, what percent are diagnosed on UA with blood culture and on direct percutaneous aspiration of the IVD?
Urine and blood culture = 40%
Percutaneous disc = 60%
What spinal segments are commonly diagnosed with FCE?
L4-L3 = 44-50%
C6-T2 = 37-42%
Where is FCE usually diagnosed?
L4-S3 = 50%
C6-T2 = 40%
What is the appearence of FCE on MRI and what percent have not lesion?
Appearence = hyperintensity on T2
21% have no lesion
Schematic representation of the cutaneous sensory innervation of the thoracic limb.
gain access to the caudal cervical vertebra, the splenius muscle needs to be exposed by separating the brachiocephalicus and trapezius muscles from each other, as indicated in this illustration
Describe dorsal dissection for AA joint
- skin incision = dorsal midline, occipital protuberance to C3 or C4.
- expose the occipitalis, cervicoscutularis, and cervicoauricularis superficialis muscles. Caudal and lateral to these muscles are the thin fibers of the platysma muscle. These muscles are incised on the midline fibrous raphe
- Separation of the paired bellies of the biventer cervicis superficially and the deeper rectus capitis attached to the dorsal spine of C2. The insertion of the rectus capitis muscle is incised along the lateral border of the spine of C2 to allow its elevation from the bone by combined sharp and blunt dissection.
D. Avoid the vertebral artery, which courses through the muscles slightly ventrolateral to the articular processes. The interarcuate (yellow) ligament covering the foramina between C1 and C2 is carefully incised to expose the spinal cord and the root of spinal nerve C1. The dorsal atlanto-occipital membrane of the foramen magnum may also be incised to expose the cranial rim of the dorsal arch of C1.
Describe dosal cervical approch for C2-C7
- skin incision occipital protuberance to the first thoracic vertebra.
- Almost transparent fibrous aponeurosis of the platysma muscle comes into view. Incision through the median fibrous raphe. This incision is deepened until the nuchal ligament (missing in the cat) is exposed.
- The dorsolateral cervical muscles (cleidocephalicus, semispinalis capitus, biventer complesus) separated by this incision are retracted laterally to expose the nuchal ligament.
- An incision is made in the rectus capitis, spinalis et semispinalis cervicus, and multifidus muscles along one side of the nuchal ligament. The incision is deepened along the lateral side of the spinous processes to the vertebral laminae.
- Elevation with a periosteal elevator and retraction of the muscles from the vertebrae are done first on the side that was incised. The insertion of the nuchal ligament is now elevated from the spinous process of the axis, and the ligament is retracted with the muscles on the side opposite the incision. The ligament remains firmly attached to the muscles of one side and cranially to the axis.
Lateral elevation of muscles from the laminae should be limited to the lateral aspect of the articular processes to avoid branches of the vertebral artery coursing ventrolaterally to the processes.
Lateral approach C3-C6:
- skin and underlying platysma- cranial border of the scapula to the wing of the atlas.
- The incised wound margins are retracted to expose the brachiocephalicus and trapezius muscles. Separate between these muscles in a dorsal to ventral, oblique direction. The superficial cervical artery and vein, which emerge from between these two muscles, are retracted caudally and ligated. Underlying these vessels are the superficial cervical lymph nodes. The brachiocephalicus muscle is transected at the level of the articular facets.
- Retraction of the transected brachiocephalicus muscle exposes the splenius muscle dorsocranially and also the serratus ventralis muscle that runs obliquely from under the cranial border of the scapula in a cranioventral direction. Cranial nerve XI (accessory nerve) crosses the serratus ventralis muscle to innervate the trapezius muscle.
— As an alternative, exposure of the C5-C7 vertebral segments can be achieved without transection of the brachiocephalicus muscle, by further extension of the separation between the brachiocephalicus and trapezius muscles in an oblique direction. The brachiocephalicus muscle is retracted cranioventrally, rather than being transected. Exposure of C6-C7 is increased further by simultaneous abduction and caudal retraction of the scapula, without the need to incise the muscular attachments on the cranial border of the scapula.
In the C3-C5 region, the brachiocephalicus muscle is incised longitudinally in the direction of the muscle fibers, instead of being transected. Using a grid technique, the divided brachiocephalicus muscle is separated to expose the underlying splenius and serratus ventralis muscles.
E. The dorsal border of the serratus ventralis muscle is elevated all the way caudally to its origin on the scapula. It may then be reflected ventrally to fully expose the underlying splenius muscle. Vascular bundles between the deep surface of the serratus ventralis and splenius muscles are ligated and divided.
F. Reflection of the serratus ventralis continues to its insertions on the lateral processes of the vertebrae, exposing the longissimus cervicis and longissimus capitis muscles. These muscles are elevated and retracted ventrally. For orientation, the prominent transverse process of C6 is located by palpation.
G, H. The splenius muscle is retracted dorsally to expose the underlying semispinalis complexus muscle. The articular facets of C3-C4, C4-C5, and C5-C6 can be palpated at the junction between the semispinalis muscle and the two longissimus muscles. The tendinous origins of the semispinalis complexus and multifidus cervicis muscles are incised from the articular facets with scissors or electrocautery. These two muscles are then elevated from the dorsal lamina of the cervical vertebrae to the base of the spinous process using a periosteal elevator.
Describe lateral approach to the brachial plexus (C5-T1)
- long curvilinear incision 3-4 cm cranially from the midpoint of the cranial border of the scapula to a point located slightly distal to the greater tubercle of the humerus.
- The platysma and fascia cervicalis are incised, exposing the cleidocervicalis, omotransversarius, and trapezius muscles (Figure 31-7, A). The superficial cervical artery and vein, which emerge between the cleidocervicalis and trapezius muscles, should be ligated.
- The omotransversarius muscle incised near spine of the scapula, retracted cranially.
- The dissection is continued medially through the deep fascia along the dorsal border of the cleidocervicalis muscle, which is withdrawn ventrally. The scapula is withdrawn caudally.
- (C5-T1) are now exposed by transecting the superficial and deep portions of the scalenius muscle
Atlas anatomy
Transverse foramen
Lateral foramen
Fovea of the dens
glenoid cavities - articulate with axis - no joint
modeified articular process articular with occipital condyles - no joint
Atlas anatomy
dorsal spinous process
cr vertebral notches = large intervertebral foramina - 2nd cervical n and intervertebral vessels
dens (odontoid process)
transverse lig
AA lig
Transverse lig
Alar ligaments
Apical lig of dens
Dorsal atlanto-axial lig
Lateral atlanto-occipital lig
Nerves of the brachial plexus and associated spinal n?
SSMAR M U
Suprascapular (C6-C7)
Subscapular (C6-C7)
Musculocutaneous (C6-C8)
Axillary (C6-C8)
Radial (C6-T2)
Median (C7-T1)
Ulnar (C8-T2)
Schematic representation of the spinal root origins of the major nerves of the lumbosacral plexus. (Based on the work of Fletcher, T. F. 1970. Lumbosacral plexus and pelvic limb myotomes in the dog. Am. J. Vet. Res. 31:35-41; and Bailey, C. S., R. L. Kitchell, S. S. Haghighi, and R. D. Johnson. 1984. Spinal root origins of the cutaneous nerves of the canine pelvic limb. Am. J. Vet. Res. 45:1689-1698.)
Dorsal atlantoaxial wiring technique. A–D illustrate the loop of wire being passed cranially under the arch of C1, then folded back and cut with the ends twisted together through the two predrilled holes in the spine of C2.
Variation = loop used to pass suture through holes
Atlantoaxial (AA) joint dorsal cross-pinning; the Kirschner wires are directed into the caudal half of the wings of the atlas.
Kishigami AA tension band
Less risk of damage to the spinal cord
crews placed into the caudoventral and sometimes the cranioventral part of the body of C2 can be used as anchors to elevate this vertebra into apposition with C1 using cerclage wire.
Transarticular screws can be inserted in lag fashion across the atlantoaxial (AA) joint, toward the medial aspect of the alar notch.
1.5 mm hole for a 1.5 mm cortical lag
approximately 30 degrees from midline
similar technique using Kirschner wires or pins (0.045 inch or 0.062 inch) has been described
Cortical bone screws can be placed into the medial aspect of each wing of the atlas caudal to the transverse foramen in a craniolateral direction
A third screw can sometimes be placed in the middle of the ventral body of C1, depending on the size of the patient; this screw can be inserted at 90 degrees to the bone surface
Two ventral C2 screw patterns have been described.
he first pattern, four cortical screws are placed into the body; one screw is placed in the middle of the caudal aspect of each of the cranial articular surfaces of C2 at the insertion point of the longus colli muscle. The screws are directed craniolaterally at 30 to 40 degrees. The second pair of screws is placed at the base of the transverse processes of C2 or C3 and is directed laterally at 30 to 40 degrees to the midline.
A second pattern uses just two cortical screws, one of which can be the screw that facilitates secure realignment. second screw can be placed in the cranial half of the C2 vertebral body.165 This latter technique additionally differs from the first screw and PMMA technique in that transarticular 0.035 to 0.062 inch threaded or nonthreaded Kirschner wires are used to secure the atlantoaxial joint, subsequently incorporating all of the screws and the wires into the PMMA
Describe the structure of nerves related to the layers surrounding the nerve.
Endoneurium surrounds each axon, which is composed of collagen fibrils, fibroblasts, and vascular tissue, and groups of axons in turn are surrounded by perineurium, which is composed of collagen and elastic fibers; the connective tissue around the entire nerve, called the epineurium, is composed of areolar connective tissue and collagen fibrils
Anatomy nerves
What are ligaments associated with spinal canal
dorsal longitudonal (thickest in cervical)
Ventral longitudonal lig
interspinous lig
yellow lig (or interarcuate)
ligament head of rib & costotransverse lig
intercapital lig - absent 1st, 11th, 12th, and 13th rib +/- 10th
Disc-associated cervical spondylomyelopathy (CSM). Top image shows ventral spinal cord compression and nerve root compression at C5-C6 caused by intervertebral disc protrusion. Dorsally, hypertrophy of the ligamentum flavum (yellow) causes mild spinal cord compression. Bottom images: A, Transverse section at the level of the C4-C5 disc region showing normal spinal cord and vertebral canal. B, Ventral compression at C5-C6 region caused by intervertebral disc protrusion and hypertrophy of the dorsal longitudinal ligament (yellow) and ligamentum flavum (causing mild dorsal compression). C, Asymmetric intervertebral disc protrusion at C6-C7, causing spinal cord and nerve root compressions.
Osseous-associated cervical spondylomyelopathy (CSM). A, Severe dorsolateral spinal cord compression at C2-C3 caused by osseous malformation and osteoarthritic changes. B, Normal C3-C4 disc region. C, Bilateral compression at C4-C5 caused by osteoarthritic changes and medial proliferation of the articular process, resulting in absolute vertebral canal stenosis and foraminal stenosis leading to spinal cord and nerve root compressions, respectively. Bottom image shows dorsal spinal cord compression at C3-C4 caused by lamina malformation and hypertrophy of the ligamentum flavum. Osteoarthritic changes are also shown at C2-C3.
Inverted cone slot. This is a modification of the traditional ventral slot that minimizes the risk of hemorrhage and subluxation.
width of the ventral decompression window limited to 20% of the cranial vertebral body.
This technique allows more complete removal of the protruded disc from the vertebral canal, with less risk of hemorrhage, compared with the traditional ventral slot. The inverted cone technique also minimizes the risk of collapse of the disc space, which could lead to postoperative nerve root entrapment and lameness as seen with the traditional slot technique
Dorsal laminectomy. Representation of a dorsal laminectomy from C4 to C7
Continous = C4-T1
high postoperative morbidity rate (70%), which can be challenging to manage in large- and giant-breed dogs.
Most dogs will improve over time (mean time to optimum recovery, ≈3.6 months), and the success rate for dorsal laminectomy ranges from 79 to 95%
30% of dogs can have signs of recurrence
What is this?
Caspar distractor
allows for controlled distraction, another option is modefied Gelpi retractor
Polymethylmethacrylate (PMMA) plug distraction technique. Representation of the PMMA plug is in place (gray). Two anchor holes in the cranial and caudal end plates prevent plug displacement. The dorsal annulus is left intact. Multiple small holes should be drilled in the ventral aspect of the vertebral bodies to promote incorporation of the cancellous bone graft (dark red) and fusion
Representation of the technique of pins and polymethylmethacrylate combined with a partial slot. A, Transverse view. Note the location of pin insertion avoiding the transverse foramina and vertebral canal. B, Lateral view, showing the position of the pins
Angle 30-35 degree, 45 degrees C7
distract
graft in slot then PMMA
73% sucess
1 site prefered can potentially do 2 sites but increases risk
Types of sacral fx
Type 1: Alar
Type 2: Foraminal
Type 3: Transverse
Type 4: Avulsion
Type 5: Comminuted
Dorsolateral approach TL spine
The skin incision slightly to side midline.
Subcutaneous fat is elevated from the deep fascia 1.5 cm lateral to the dorsal spinous
Both layers of the fascia are incised 5 to 10 mm from the dorsal spines
The multifidus and longissimus muscles are separated by blunt dissection of the intermuscular septum.
The tendons are attachments of the longissimus muscle to the accessory processes of the vertebrae. The dorsal branches of the spinal nerves emerge just ventral to these tendinons and the intervertebral disk space is located caudoventral to the insertions.
An elevator is used to remove muscle and fascia overlying each disk. The insertions of the longissimus tendons are used as landmarks for locating the disk spaces. A nerve root retractor allows the spinal nerves to be retracted cranially and protected from the elevation and fenestrating instruments.
T10-T11 is the most cranial disk accessible and L5-L6 the most caudal (tobias says T9-L7)
The thoracic spine is supplied by spinal branches (A) from the intercostal arteries (B), which enter the vertebral canal via the intervertebral foramina. The internal vertebral venous plexus drains into the major veins of the dorsal thorax (C), mainly in the azygous vein.
Dorsal view of the muscles encountered during the dorsal approach to the cranial thoracic spine.
Approach to lateral TL spine
The deep thoracolumbar fascia is incised to reveal a second layer of fat and the underlying muscles. The lateral processes can now be palpated quite easily. To approach the thoracic spaces, it is necessary to transect some bundles of the serratus dorsalis muscle. D. The thirteenth rib is a good place to start because it allows counting cranially and caudally to identify the other vertebrae. Blunt dissection and separation of the fibers of the iliocostalis lumborum muscle allow the proximal end of the thirteenth rib to be exposed. A periosteal elevator is used to clear soft tissues from the cranial border of the rib and the lateral surface of the disk. Staying close to the cranial edge of the rib and strong cranial retraction of the muscle will protect the spinal nerve and vessel (see Plate 20D inset drawing). Care must be taken to prevent penetrating the thoracic pleura when clearing the disk surface. The lumbar disks are exposed by blunt separation of muscle tissue over the end of the appropriate lateral process. Confining the dissection and elevation to the dorsal surface of the process will protect vessels running along the cranial and caudal borders of the tip of the process. The elevation of muscle tissue is continued medially until the disk space is exposed. As the vertebral body and disk are approached, all elevation and retraction should be from a caudal-to-cranial direction to protect the spinal vessel and nerve. A blood vessel will be seen crossing the surface of the disk in the lower lumbar spaces, and it is usually lacerated during the fenestration process.
What are the different Funquist laminectomies
During Funkquist type A dorsal laminectomy, remove zygapophyseal joints and pedicles to expose the dorsal half of the spinal cord. B, During Funkquest type B dorsal laminectomy, remove the dorsal lamina, taking care to preserve the cranial and caudal portions of the zygapophyseal joint. C, When performing deep dorsal laminectomy, remove the dorsal lamina, the entire zygapophyseal joint, and pedicles to the level of the ventral aspect of the vertebral canal.
Cerebrospinal Fluid Characteristics in Dogs With Thoracolumbar Disc Herniation
Chronic disc hernias can produce a “wrapping” effect: The cord spreads out on either side of the vertebral canal floor around the margins of the protruded material. B, Craniolateral view of thoracolumbar corpectomy: A lateral slot has been drilled under the prolapsed material through the intervertebral disc and the vertebral epiphysis of two adjacent vertebral bodies. Excision of the protruded disc has been achieved when the spinal cord has returned to its normal position
his surgery involves the creation of a slot in the vertebral body, ventral to the intervertebral foramen. The slot is the length of each vertebra, centered over the disc. The pedicle and lamina remain intact
The hypogastric nerve is derived from the first through fourth lumbar spinal cord segments and provides adrenergic input to the internal urethral sphincter, the pelvic (parasympathetic) ganglia, and the detrusor muscle. Sympathetic input to the pelvic ganglia inhibits parasympathetic activity during urine storage. The hypogastric nerve contains sensory fibers from the bladder wall and is involved in bladder nociception.
To empty the urinary bladder, adrenergic input to the bladder is decreased, allowing increased detrusor muscle and decreased internal urethral sphincter tone. Cholinergic stimulation (pelvic and pudendal nerves) results in detrusor muscle contraction and external urethral sphincter relaxation.
alpha-adrenergic antagonists, such as phenoxybenzamine (0.25 to 0.5 mg/kg PO every 12 to 24 hours) or prazosin (1 mg/15 kg PO every 8 to 24 hours)
Schematic relationship between vertebral bodies and spinal cord segments in the lumbosacral spine.
Pathologic changes in degenerative lumbosacral stenosis contributing to compression of nerve roots include the following: (A) bulging of the disc or annulus fibrosus; (B) thickening of the dorsal annulus fibrosus; (C) mechanical instability with subluxation of L7-S1; (D) osteophyte formation within spinal canal and around the articular process joints; (E) thickening of the joint capsule of the articular process joints; and (F) thickening of the ligamentum flavum (interarcuate ligament).
Sagittal computed tomography (CT) scan demonstrating osteochondrosis lesion of the dorsal aspect of the S1 end plate (arrow). This is the most common area for osteochondrosis lesions to be seen in the lumbosacral region.
Flexion (top) and extension (bottom) sagittal computed tomography (CT) images demonstrating exacerbation of L7-S1 disc protrusion (arrow) and nerve root compression in the extended position.
Postoperative lateral (A) and ventrodorsal (B) radiographs showing positive-profile end-threaded pins driven into the body of L7 and S1 and polymethylmethacrylate used to stabilize the lumbosacral region.
Postoperative lateral (A) and ventrodorsal (B) radiographs showing positioning of the SpondyloFitz bolt with dorsal augmentation with screws, pins, and methylmethacrylate.
What are the 3 compartments of the spinal colum?
Dorsal = spinous process, veterbral lamina, articular process, vertebral pedicles, dorsal ligamentous complex (ligaments and capsule)
Middle = dorsal longitudinal lig, dorsal annulus, dorsal vertebral body
Ventral = remainer vertebral body and AF, NP, ventral longtudinal lig.
Instabilty greatet to least = Failure of the body > disc > articular facet
If greater than 1 compartment compromised = instability
What are landmarks for placement of spinal pins?
Entry points:
thoracic = accessory process or tubercle of rib
lumbar = btwn base transverse process and accessory process
Aim: medial lateral and either cr-ventral or cd ventral towards endplate
Insertion angles = T10-T13 (30-35, 60, 22-44), L1-L6 (30-25, 60, 60)
What are other techniques for spinal stablization besides PMMA/pins, Ex-Fix and SOP plate? These techniques are not recommended
Spinous process plating - (bilatearl metal: Auburn spinal plate, Lubra plate (propensity for failure and granuloma formation). Plates connect through (metal) or between (plastic) spinous processes.
Modified segmental fixation: multiple pins in dorsal lamina with encirlaing ortho wire
Spinal stapling: Holes at base spinous process with steel pins (bent in staple shape)
Complications - ishchemic necrosis spinous process, SP fracture, device pull out
What is this?
Scoville-Haverfield Laminectomy retractor
for cervical fracture distraction
Cross-sections of the L4 vertebra illustrating the basivertebral vein (arrow), which anastomoses with the internal vertebral venous plexus. This vessel can be a source of hemorrhage during pin placement.
Cross-section of C5 vertebra, illustrating implant corridors for bicortical implants (green) and monocortical implants (purple), with proximity to the transverse foramen (A), vertebral artery (B), vertebral vein (C), and vertebral canal (D
Ventrodorsal (A) and lateral (B) radiographs of UniLock System stabilization of a cervical lesion at C6-C7, using monocortical screws
Ventrodorsal (A) and lateral (B) radiographs of a C2 fracture-luxation stabilized with bone screws and polymethylmethacrylate (PMMA)
How to fix
Lateral (A) and dorsoventral (B) radiographs of pin/polymethylmethacrylate (PMMA) stabilization of an L7-S1 fracture-luxation. Note the air pockets in the dorsal aspect of the PMMA. This weakens the pin/PMMA construct. Vacuum mixing of the cement and application while still somewhat viscous will help to minimize air pocket formation.
LS safe corredors for pins?
L7 vertebra illustrating the wide pedicle available for implant purchase
Cranial implants = intact pedicles L7: pins just cd to base of cr. articular processes (directed ventrally or sl. laterally 0-5 degrees)
Cd implants = sacrum: same L7 or shaft ilium (enter sacrum cd/lat to cd articular process of L7, directed caudal-ventrally across SI joint (averge angle 29 saggital, 20 transverse)
Fractures of the body of the axis
Fractures of the body of the axis are best stabilized through the ventral approach. The thin central body of C2 provides little purchase for implants. Pins or screws must be inserted into the cranial or caudal aspect of the body. Construct stability should be increased by crossing the atlantoaxial joint with implants (Figure 34-11). The cranial pins are directed in a craniolateral direction from C2 to C1. They should be placed at approximately a 30 to 35 degree angle in the sagittal plane and at a 40 to 45 degree angle in the transverse plane. To avoid the transverse foramen and vertebral artery, a point just medial to the alar notch of C1 can be used as a target during placement. Caudal C2 pins can be inserted in a transverse plane, directed laterally at a 30 to 50 degree angle
The illustration depicts the anatomic locations where intracranial hemorrhage can occur secondary to traumatic brain injury. Differentiation between hemorrhages in the anatomic locations subdural (hemorrhage within the dura mater) and epidural (superficial to the dura mater) is challenging based on imaging alone. Intraventricular and subarachnoid (within the subarachnoid space) hemorrhages are not depicted.
Modified Glasgow Coma Scale
Motor
Brainstem reflexes
Level of conscisous
Graded 1-6
schematic illustration of a typical ventriculoperitoneal shunting device
for foramen magnum decompression in dogs with Chiari-like malformation. A, Occipitalis muscle; B, median raphe; C, cervicoscutularis and cervicoauricularis superficialis muscles.
Illustration of deeper structures encountered during foramen magnum decompression in dogs with Chiari-like malformation A, Biventer cervicis muscle; B, rectus capitis dorsalis muscle; C, multifidus muscles; D, nuchal ligament.
A) the region of the caudal occiput and the dorsal aspect of C1 vertebra removed for foramen magnum decompression, and (B) the extent of the foramen magnum decompression once completed.
Figure 37-24 Sagittal T2-weighted MR image of a dog with atlanto-occipital overlapping. In addition to the overlap, atlantoaxial instability and occipital dysplasia are evident. A, Cranial-most aspect of the dorsal arch of C1; B, body of C1; C, dens; D, ventral-most aspect of the supraoccipital bone.
