Tobias Rounds Questions (From Powerpoints) Flashcards
Which of the following is false regarding hemilaminectomy?
a. The hemilaminectomy is the most common procedure used to provide exposure to the vertebral canal and spinal cord in dogs and cats.
b. The procedure results in removal of only the lamina on one side of the vertebra; the pedicle is left intact.
c. Hemilaminectomy provides exposure to the ventral, dorsal, and lateral (unilateral) aspects of the spinal cord and vertebral canal.
d. Hemilaminectomy can be performed via a dorsal or dorsolateral approach to the vertebral column.
B is FALSE.
Hemilaminectomy is the removal of half of the vertebral arch, including the lamina, pedicle, and articular process.
True or False: Variations of the hemilaminectomy include the mini-hemilaminectomy and the pediculectomy.
True. These procedures are meant to preserve the zygapophyseal joint, thus resulting in less mechanical instability.
Which of the following is true regarding dorsal laminectomy?
a. Various modifications of this technique can be used, including Funkquist A, Funkquist B, Funkquist C, and modified dorsal laminectomy.
b. Funkquist A involves removing the spinous process, laminae, articular processes, and approximately a quarter of the dorsal portion of the pedicles of a vertebra to gain access to the vertebral canal.
c. Funkquist B leaves the articular processes intact, but removes the pedicles, spinous process and laminae.
d. For the modified dorsal laminectomy, the laminae, spinous process, and caudal articular processes are removed.
D is TRUE.
- a is false because there is no Funkquist C
- b is false because it is approx 1/2 of the dorsal portion of the pedicles, not 1/4
- c is false because Funkquist B leaves the articular processes and pedicles intact but removes the spinous process and laminae.
Sensitivity is defined as the number of ______ animals identified by a test divided by the total number of animals with the disease.
Positive.
Sensitivity= TP/(TP+FN)
Specificity is defined as the number of ______ animals identified by a test divided by the total number of animals without disease.
Negative.
Specificity= TN/(TN+FP)
Define prevalence?
Prevalence is the proportion of animals in a population affected by a disease.
Define accuracy?
Accuracy is the proportion of correct diagnoses a test provides.
Accuracy of radiographs for identification of intervertebral disc herniation is ___%?
50-60%
What are the three different basic myelographic patterns to describe location of pathology?
Extradural, intradural-extramedullary, intramedullary
True or False: Length of the intramedullary pattern:length of L2 vertebra ratio after myelography has been used to predict outcome in dogs that lack nociception.
True.
Name four factors that positively affect the performance of noncontrast CT for detecting intervertebral disc herniation?
- Use of multiplanar reconstruction techniques
- Chronic history of disc herniation
- Chondrodystrophic breed type
- The presence of mineral dense intervertebral disc material.
The flow of cerebrospinal fluid within the subarachnoid space of the spinal cord is _____ to ______, and sampling CSF _____ to the location of the pathology might be less likely to reflect abnormalities?
The flow of cerebrospinal fluid within the subarachnoid space of the spinal cord is CRANIAL to CAUDAL, and sampling CSF CRANIAL to the location of the pathology might be less likely to reflect abnormalities.
Where can cerebrospinal fluid be acquired from in dogs?
- Cerebellomedullary cistern
- Lumbar subarachnoid space
In one prospective study of 24 dogs, MRI had ____% sensitivity for determining the location and side of the intervertebral disc herniation, whereas CT myelography had sensitivities of ____% for detecting the site and ___% for detecting the side of intervertebral disc material.
MRI had 100% sensitivity for determining the location and side of the intervertebral disc herniation, whereas CT myelography had sensitivities of 90% for detecting the site and 55% for detecting the side of intervertebral disc material
What percentage of dogs with FCE have a recognizable lesion/particular signal pattern on MRI?
78.8%
In a prospective MRI study, Only ___% of dogs with T2W hyperintensity greater in cranial-caudal length than 3 times the length of L2 returned to voluntary ambulatory status.
20%
Name two findings regarding prognosis and T2W hyperintensity in MRI of the spine:
- All dogs lacking T2W signal changes within the spinal cord recovered voluntary ambulation
- T2W length ratio was an independent predictor of functional outcome with the odds of recovery reduced by 1.9 fold per unit of hyperintensity
Is T2W hyperintensity a good or bad finding on spinal MRI?
BAD! Presence is correlated with reduced odds of recovery. Longer areas of hyperintensity = worse prognosis.
What are the three strategies that comprise medical management of IVDD?
- Enforced rest to allow healing of the annulus
- Use of analgesics, muscle relaxants and anti inflammatories
- Physical rehabilitation
True or False: Tobias currently does not recommend any corticosteroids in the management of IVDH, with or without surgical intervention.
True.
What is the percentage range for successful surgical outcomes for dogs with normal nociception?
72-100%
What is the percentage range for successful surgical outcomes for dogs with paraplegia with absent nociception?
43-62%
True or False: The location of disc herniation is associated with outcome?
FALSE
The duration of therapy in dogs with UTI secondary to neurogenic bladder dysfunction should be _____ than that recommended for a simple UTI.
Longer. Some authors recommend a course of 3-6 weeks for persistent UTI and reculturing urine 2-3 days after completion of antibiotics.
What is “spinal walking”?
Use of pelvic limb reflexes, trunk muscles, and any remaining upper motor neurons to generate a gait as opposed to conscious voluntary walking.
What breeds have the highest prevalence of vertebral malformations?
Screw-tailed breeds (English Bulldog, Frenchies, Boston Terriers, Pugs)
What are butterfly vertebrae?
Butterfly vertebrae are characterized by a sagittal cleft within the affected vertebral body. This cleft may be visible on a dorsoventral radiographic view, creating the specific appearance of the affected vertebra.
What is the condition in which there is failure of the laminae to fuse dorsally?
Spina bifida.
Dermoid/pilonidal sinuses are a congenital condition wherein the skin fails to completely separate from the neural tube during embryonic development. What breed is predisposed to this?
Rhodesian Ridgeback.
What are the five groups of clinical signs of spinal cord disease?
(1) reduction or loss of voluntary movement
(2) spinal reflex abnormalities
(3) alterations in muscle tone
(4) muscle atrophy
(5) sensory dysfunction
True or False: Lesions affecting the C1-C5 spinal cord segments may result in increased thoracic limb stride length, and those affecting the C6-T2 spinal cord segments may result in reduced stride length.
True.
What is a two-engine gait and where does this neurolocalize?
Short thoracic limb stride with long pelvic limb stride (C6-T2).
What is the most common clinical sign of ‘root signature’ lesion?
Holding a thoracic limb up in a partially flexed position.
What is the zygapophyseal joint?
The diarthrodial joint of the articular processes.
Diarthrodial = Mobile joints with cartilage at the articular surfaces, a joint capsule and synovial fluid. An articular cavity is present between joint surfaces.
Name a nutritional cause of cervical spinal cord disease?
Hypervitaminosis A in cats.
What two breeds of dog are associated with degenerative cervical spinal cord disease?
Rottweilers (C1-C5) and Australian Cattle Dogs (C6-T2).
When making a ventral approach to the atlantoaxial joint, surgical orientation can be provided by palpation of a pointed ventral prominence on the caudal aspect of C1, the _________.
Ventral tubercle. This is the ventral midline location of the C1-C2 joint space.
True or False: During a lateral approach to the cervical vertebral column, abduction and retraction of the scapula can facilitate access to the articulation of the C6-C7 vertebrae.
True.
List four indications for a ventral approach to the cervical vertebral column:
A. Ventral slot/intervertebral disc fenestration
B. Fracture fixation
C. Atlantoaxial stabilization
D. Cervical spondylomyelopathy
List three indications for a dorsal approach to the cervical vertebral column:
A. Dorsal laminectomy
B. Fracture fixation
C. Atlantoaxial stabilization
Where does the first cervical spinal nerve and its associated vasculature pass through?
The lateral vertebral foramen.
What is the cranioventral peg-like projection on the axis vertebra called?
The dens or odontoid process.
What are the ligaments that stabilize the dens/odontoid process of the axis?
- Held in the ventral aspect of the vertebral foramen by the transverse ligament and by the apical ligament attached to the basiocccipital bone.
- Held to the occipital condyles by bilateral alar ligaments.
What breeds of dogs are most often affected/predisposed to atlantoaxial instability and subluxation?
Small/miniature breed dogs - Yorkies, Chihuahuas, mini/toy poodles, Pomeranians, Pekingese.
Why are small breed dogs predisposed to atlantoaxial instability?
Their dens is prone to maldevelopment due to aberrations in physeal growth plate closure, dysplasia, hypoplasia, dorsal angulation, separation of the dens, absence of transverse ligament etc.
Traumatic atlantoaxial subluxation can occur in dogs of any breed - what happens when this occurs?
Forceful overflexion of the head may tear the ligaments or cause a fracture of the dens or laminae of the axis.
What is the angle between the atlas and the axis that is more predictive of instability (vs decreased overlap)?
162 degrees
What are possible treatments for atlantoaxial instability?
Conservative - external coaptation with rigid cervical brace until ligaments hopefully heal (at least 6wk).
Surgical- Goal is bony ankylosis of the atlantoaxial joint that permanently stabilizes the articulation.
Dorsal and ventral approaches for stabilizing the atlantoaxial joint exist. Which approach is preferred for fractures?
Ventral approach.
Dorsal and ventral approaches for stabilizing the atlantoaxial joint exist. What is a contraindication for the dorsal approach?
Compression of the spinal cord due to dorsal deviation of the dens.
Osseous fusion generally is not achieved with dorsal techniques for stabilizing the atlantoaxial joint because they cannot resist movement in directions other than flexion, but the dorsal technique may be preferred in what cases?
Dorsal stabilization techniques may be preferable in dogs with small body weight (<2 kg), which may prohibit the use of metallic implants ventrally, and in those dogs in which ventral stabilization techniques initially fail.
What are the six classifications of nerve injury?
Class 1 - neuropraxia
Class 2 - axonotmesis
Class 3 - neurotmesis with intact perineurium
Class 4 - neurotmesis with disrupted perineurium
Class 5 - neurotmesis with severed nerve
Class 6 - combines several of the above
Define neuropraxia?
Neuropraxia is the mildest form of traumatic peripheral nerve injury with no loss of nerve continuity. The axons maintain their anatomical integrity but become dysfunctional/demyelinated. This condition results in blockage of nerve conduction and transient weakness or paresthesia and is treated conservatively.
Define axonotmesis?
Axonotmesis, the second level of PNI, is characterized by a disruptive lesion of the axon and its myelin coating. The integrity of the outer connective tissue covers, namely the perineurium and the epineurium, remains, ensuring that the anatomical shape of the nerve is maintained. The prognosis with conservative tx tends to still be excellent.
Define neurotmesis?
Severing of a nerve (the axons) it comes in three levels:
The third and fourth levels of PNI where the axons, myelin sheaths, and endoneurium are disrupted, but the fascicular alignment and integrity of the outer layers of collagen are maintained.
In the third level, the perineurium and epineurium are intact. Recovery with conservative tx is possible but may take months.
In the fourth level, all layers except the epineurium are disrupted.
In the fifth level of PNI, the nerve and all associated structures are severed. Recovery without surgery for 4th and 5th level is almost impossible.
True or False: The site of spinal nerve root injury is usually intradural, where the nerve roots arise from the spinal cord.
True.
What forms the brachial plexus?
It is formed from the ventral branches of the sixth cervical through the second thoracic spinal cord segments, respective spinal nerve roots, and spinal nerves.
In ____% of dogs, the brachial plexus also contains the fifth cervical spinal cord segment and its spinal nerve roots and spinal nerve.
24%
Partial injuries to the brachial plexus most commonly involve the spinal nerve roots in the _______ portion of the brachial plexus.
Caudal.
Partial injuries to the brachial plexus most commonly involve the spinal nerve roots in the _______ portion of the brachial plexus.
Caudal.
True or False: If neurotmesis exists, routine surgical anastomosis of the affected nerves are recommended.
True. These injuries are less likely to respond to conservative therapy.
Axonal regrowth can reach at least ____ cm within a 4-month period when avulsed nerves are reimplanted into the spinal cord.
10-15cm
What is neurotization?
Neurotization is sacrificing a donor nerve (motor) to restore a recipient nerve (motor).
What is Cross-neurotization?
Cross neurotization is sacrificing a donor nerve (sensory) to restore a recipient nerve (motor).
The ______ is thicker in the cervical vertebral column, offering greater resistance to dorsal herniation of nucleus pulposus in this region?
Dorsal longitudinal ligament.
What percentage of intervertebral disc herniation occurs in the cervical spine?
14-25%
Extradural material with a high T2-weighted signal intensity, often with a “seagull” shape on transverse images, is likely associated with what?
Hydrated nucleus pulposus extrusion.
A dorsal laminectomy can be extended to _____% the length of the laminae cranial and caudal to the lesion.
75%
True or False? Fenestration should not be performed in dogs weighing more than 30 kg due to risk of vertebral collapse or subluxation after removing a large portion of intervertebral disc.
True.
A ventral slot is centered over the junction of the annulus fibrosis with the ventral aspect of the adjacent vertebral bodies and should not be greater than ___% the length and ___% the width of the bodies being drilled.
33% length, 50% width.
True or False: Cervical IVDD dogs with ventilatory compromise have lesions cranial to origin of phrenic nerve.
True. The neurons of the medullary respiratory center enter the spinal cord via the reticulospinal tracts, which project to cord segments C5 through C7, which give rise to phrenic nerve.
Risk for cardiac arrhythmias is _______ with ventral slot compared to thoracolumbar decompression surgery.
Greater.
Long-term follow-up for ventral slot decompression of caudal cervical intervertebral disc protrusion in large-breed dogs revealed only a __% success rate, and it was concluded that dynamic compressive lesions may need a stabilization procedure.
66%
Cervical spondylomyelopathy is more commonly diagnosed in _____ sized dogs?
Large to giant.
What is another term for Wobbler’s Syndrome?
Cervical spondylomyelopathy.
The pathophysiology of cervical spondylomyelopathy involves both _____ and ______ factors.
Static and dynamic.
Static factors in cervical spondylomyelopathy include:
Foraminal stenosis, which can be disc-associated or osseous-associated.
Disc-associated stenosis in cervical spondylomyelopathy is typically seen in middle-aged large breed dogs. Most commonly in which breed?
Doberman Pinschers
What is the inheritance pattern for cervical spondylomyelopathy in Doberman Pinschers?
Autosomal dominant with incomplete penetrance.
**An autosomal dominant condition is usually represented in each generation, but with reduced penetrance, a generation may appear to be “skipped” because of the lack of phenotypic expression.
Is it acceptable to use the term instability when describing cervical spondylomyelopathy with dynamic compression? Why or why not?
No, it is not acceptable. The fact that the spinal cord appears to be compressed upon neck flexion or extension on a myelogram does not mean that there is inherent instability.
What are common clinical signs seen in dogs with cervical spondylomyelopathy?
- Gait abnormalities are most common; proprioceptive ataxia, even in the absence of postural reaction deficits
- Neck pain or cervical hyperesthesia (5% of dogs)
Most commonly signs are chronic and progressive, though acute does happen.
Name three ways corticosteroids can help in the medical management of cervical spondylomyelopathy:
Decrease vasogenic edema from chronic compression
Protect from glutamate toxicity
Reduce apoptosis of cord
What is the success rate of medical management for cervical spondylomyleopathy?
54%
True or False: The most common type of cervical spondylomyelopathy is osseous compression?
False, it’s disc-associated.
When using a fat graft to prevent postoperative laminectomy membrane formation, graft thickness should be limited to ____mm to prevent neurologic complications.
<5mm
For distraction-stabilization of cervical spondylomyelopathy using pins and PMMA, what direction and at what angle should you drive the pins?
Dorsolaterally at 30-35 degrees (45 for C7)
What are some complications associated with treatment of cervical spondylomyelopathy?
Neurologic deterioration
Vertebral foramen and trasverse foramina penetration with implant placement
Adjacent segment syndrome - the “domino” effect” (occurs in approximately 20%) of cases especially after distraction-stabilization techniques
Laminectomy membrane (fat graft/ cellulose membrane to minimize occurence)
Implant failure,
Collapse of intervertebral foramina
Insufficient decompression
What is the percentage of dogs reported to improve following surgical treatment for disc-associated cervical spondylomyelopathy?
80%
The overall recurrence rate for all direct and indirect decompressive procedures to treat disc-associated cervical spondylomyelopathy is ___%?
24%