Cervical Vertebral Stenotic Myelopathy / Wobbler's

Question 1

What causes the ataxia and weakness in a horse with Wobblers?

Answer 1

narrowing of the cervical vertebral canal or malalignment/ malformation of the cervical vertebrae that causes compression of the spinal cord.

Question 2

T/F: stenosis of the vertebral canal is the most common abnormalitiy associated with Wobblers

Answer 2

true

Question 3

what are the main differences between type 1 and type 2 Wobblers?

Answer 3

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.

Question 4

What are some changes you can see radiographically with Type 1 CVSM (Wobblers)?

Answer 4

the changes reflect malformation
- enlargement of the physes
- caudal extenson of the dorsal vertebral arch
- angulation between vertebrae
- OCD of the articular processes

Question 5

What are some changes you can see radiographically with Type 2 CVSM (Wobblers)?

Answer 5

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

Question 6

T/F: CVSM is the leading cause of non-infectious spinal ataxia in horses

Answer 6

true

Question 7

The pathogenesis of Type 1 CVSM is multifactorial. What are some of the factors that may play a role?

Answer 7

• genetic predisposition
• trauma
• exercise
• nutrition (Excessive digestible energy or phosporus, or copper deficiency)

Question 8

The following are potential sg/history components associated with which type of CVSM?
- Recent

Answer 8

recent rapid growth or weight gain
foal larger than similarly-aged foals.
acute ataxia or gait abnormalities following trauma

Question 9

Older horses that develop Type 2 CVSM may have a history of…

Answer 9

chronic, gradual development of neurological signs or poor performance.

Question 10

What are some possible physical exam findings for a horse with CVSM?

Answer 10

• 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

Question 11

what are 4 differential diagnoses for CVSM?

Answer 11

1. EPM
2. Trauma
3. Equine degenerative myeloencephalopathy
4. equine herpesvirus myeloencephalopathy

Question 12

why would west nile virus NOT be an appropriate additional differential for a horse with suspect CVSM?

Answer 12

WNV causing encephalitis that affects the cerebrum therefore there would be mentation changes.
In horses affected with CVSM, mentation should be normal.

Question 13

How do you definitively diagnose CVSM?

Answer 13

Imaging – either plain lateral radiographs, myelogram, or CT.

Usually CSF cytology is normal. You may see some xanthochromia due to trauma or EHV.

Question 14

What are changes you could see on radiographs in a patient with CVSM?

Answer 14

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)

Question 15

Which radiographic view allows better visualization of the articular facet joints?

Answer 15

oblique views of the cervical vertebrae

Question 16

Why does subjective assessment of radiographs NOT adequately disciminate between horses with and without CVSM?

Answer 16

compression can happen at sites that look normal
and sites can have malformation with no compression.

Question 17

Why is it difficult to evaluate DJD in cases of CVSM?

Answer 17

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.

Question 18

What is a sagittal ratio?

Answer 18

a ratio of the vertebral canal width to the height of the vertebral body.

Question 19

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?

Answer 19

Myelography

this requires gen anesthesia. contrast agent is injected into the AO space and rads are taken in neutral, flexed, and extended positions.

Question 20

which cervical vertebrae most commonly show static compression?

Answer 20

C5/6 and C6/7

Question 21

which cervical vertebrae most commonly show dynamic compression?

Answer 21

C3/4 and C4/5

Question 22

What myelogram findings would indicate a diagnosis of CVSM?

Answer 22

• 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

Question 23

T/F: myelograms can only determine lateral compression, not dorsoventral compression in cases of CVSM

Answer 23

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.

Question 24

T/F: in flexion, some normal ventral dye column attenuation can occur in a normal horse.

Answer 24

true

Question 25

What is the MEDICAL treatment for CVSM?

Answer 25

If < 1 year old:
- restricted exercise
- restricted protein and carb intake (lower BCS)
- balanced vitamins and minerals
- Vit A and E 3x recommended dose
- balanced selenium

In older horses:
- may inject facets (this is more effective in horses without neuro deficits)

Question 26

What is SURGICAL treatment of CVSM?

Answer 26

Ventral stabilization of vertebrae to stop repetitive trauma to the spinal cord. It is essentially fusing the vertebrae with implants so no more dynamic compression occurs.

this is followed by strict stall rest (1 month), stall rest and handwalking (1 month), small paddock (1 month), then unlimited turnout with no work (1 month), then you can try groundwork and saddle after 6 months (be aware of the risks).

Question 27

T/F: a young horse with 4 CVSM lesions is a good candidate for surgical treatment as opposed to medical.

Answer 27

false – a young horse with 1-2 lesions and mild-mod clinical signs that are not chronic is a better candidate for surgery.

the surgery is only expected to improve the horse 1-2 grades adn can take 6-12 months. It is very expensive and owners/riders must be aware of the risk that they may not ever be normal again.

Question 28

what is the prognosis for CVSM?

Answer 28

depends on: age, severity of defects, duration of neuro signs, and expected performance level

without tx .. prog=poor

young + medical tx –> 80-83% improve

ventral stabilization sx –> 80% improve, 45-60% return to use.