Cervical Vertebral Stenotic Myelopathy / Wobbler's Flashcards
What causes the ataxia and weakness in a horse with Wobblers?
narrowing of the cervical vertebral canal or malalignment/ malformation of the cervical vertebrae that causes compression of the spinal cord.
T/F: stenosis of the vertebral canal is the most common abnormalitiy associated with Wobblers
true
what are the main differences between type 1 and type 2 Wobblers?
type 1: YOUNG, mostly TB, multifactorial cause, MALFORMATION of the vertebrae and/or canal leads to compression of the spinal cord
type 2: OLDER horse, all breeds, DEGENERATIVE cause, osteoarthritic changes of the articular process leads to compression of the spinal cord.
What are some changes you can see radiographically with Type 1 CVSM (Wobblers)?
the changes reflect malformation
- enlargement of the physes
- caudal extenson of the dorsal vertebral arch
- angulation between vertebrae
- OCD of the articular processes
What are some changes you can see radiographically with Type 2 CVSM (Wobblers)?
the changes will reflect degeneration
- DJD of the articular processes
- wedging of the vertebral canal
- periarticular proliferation
- synovial or epidural cysts
- fractures of articular processes
T/F: CVSM is the leading cause of non-infectious spinal ataxia in horses
true
The pathogenesis of Type 1 CVSM is multifactorial. What are some of the factors that may play a role?
- genetic predisposition
- trauma
- exercise
- nutrition (Excessive digestible energy or phosporus, or copper deficiency)
The following are potential sg/history components associated with which type of CVSM?
- Recent
recent rapid growth or weight gain
foal larger than similarly-aged foals.
acute ataxia or gait abnormalities following trauma
Older horses that develop Type 2 CVSM may have a history of…
chronic, gradual development of neurological signs or poor performance.
What are some possible physical exam findings for a horse with CVSM?
- abnormally worn hooves
- concurrent DOD
- signs of nerve root damage (pain or focal muscle atrophy)
-ataxia and paresis that localizes to the cervical spinal cord (symmetric) - if repetitive trauma to spinal cord -> damage to white matter –> more severe pelvic limb signs
what are 4 differential diagnoses for CVSM?
- EPM
- Trauma
- Equine degenerative myeloencephalopathy
- equine herpesvirus myeloencephalopathy
why would west nile virus NOT be an appropriate additional differential for a horse with suspect CVSM?
WNV causing encephalitis that affects the cerebrum therefore there would be mentation changes.
In horses affected with CVSM, mentation should be normal.
How do you definitively diagnose CVSM?
Imaging – either plain lateral radiographs, myelogram, or CT.
Usually CSF cytology is normal. You may see some xanthochromia due to trauma or EHV.
What are changes you could see on radiographs in a patient with CVSM?
Bony malformation of the cervical vertebrae
- flare of caudal vertebral epiphysis
- abnormal ossification of articular processes (esp with type 2)
- malalignment between adjacent vertebrae
- extension of dorsal laminae
- DJD of articular processes (esp type 2)
Which radiographic view allows better visualization of the articular facet joints?
oblique views of the cervical vertebrae
Why does subjective assessment of radiographs NOT adequately disciminate between horses with and without CVSM?
compression can happen at sites that look normal
and sites can have malformation with no compression.
Why is it difficult to evaluate DJD in cases of CVSM?
It occurs most commonly caudally – its really hard to get good images this caudally because the shoulder is in the way and we do not take DV images.
And, many normal older horses can develop DJD so it can be difficult to say if it is assoc with compression or not.
What is a sagittal ratio?
a ratio of the vertebral canal width to the height of the vertebral body.
which diagnostic test can confirm spinal cord compression, identify the location and number of lesions, and differentiate between static vs dynamic compression in potential case of CVSM?
Myelography
this requires gen anesthesia. contrast agent is injected into the AO space and rads are taken in neutral, flexed, and extended positions.
which cervical vertebrae most commonly show static compression?
C5/6 and C6/7
which cervical vertebrae most commonly show dynamic compression?
C3/4 and C4/5
What myelogram findings would indicate a diagnosis of CVSM?
- reduction in the thickness of contrast columns (< 2 mm)
- attenuation/thinning of dorsal and ventral column by >50%
- complete attenuation of ventral column with 50% attenuation of dorsal column
T/F: myelograms can only determine lateral compression, not dorsoventral compression in cases of CVSM
false – they can only determine dorsoventral compression.
CT and MRI would be able to identify dorsal, ventral and lateral. but this is difficult to do in horses.
T/F: in flexion, some normal ventral dye column attenuation can occur in a normal horse.
true
