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What is IVDD?

• chondroid degeneration
• extrusion of degenerate nucleus
• Acute --> spinal cord trauma (contusion or compression)


What animals tend to be affected by IVDD?

• Chondrodystrophoid breeds (Dachshunds, Basset Hounds, beagles, corgis)
• Potentially non-chondrodystrophoid breeds and large breeds as well (less common)
• Young (>3yo) to middle age and older


What are radiographic signs for IVDD? Which of these are specific for type 1 and 2?

• Spondylosis deformans (bony bridging) (Type 2)
• Mineralisation of IVD (seen with type 1 / chondroid degeneration) - (Type 1)
• Narrowed IVD space
• End-plate sclerosis (Type 2)
• Others: narrowed articular process joint space (Type 1), increased opacity of intervetebral foramen, spondylosis
• Radiographs aren't diagnostic for spinal cord compression


Outline advantages/ disadvantages of radiographs

- ADVANTAGES – widely available, cheap, GA not essential but possible
- DISADVANTAGES – doesn’t show SC or nerve roots, therefore cannot confirm presence or site of spinal compression, difficult to interpret if not optimally positioned, radiation exposure


What is myelography?

contrast into subarachnoid space + radiograph


What is an extradural pattern

impression of outline of disc material – doesn’t directly visualised disc material


Advantages/ disadvantages of myelography

- ADVANTAGES: more available and cheaper than CT or MRI, good visualisation of extradural compression of sub-arachnoid space
-DISADVANTAGES: possible morbidity or neuro deterioration, technical skill/ operator dependent, possible adverse effects (post-myelographic seizures, infection), does not image spinal cord parenchyma, radiation exposure


Advantages/ disadvantages of CT?

• ADVANTAGES: allows transvere imaging (reformatted into any plane), excellent spatial resolution, excellent visualisation of both or other mineralised tissue.
• DISADVANTAGES– cost, availability, poor visualisation of SC parenchyma, may not visualised compression if not mineralised


Advantages/ disadvantages of MRI

• ADVANTAGES: imaging in any plane, excellent contrast resolution of soft tissues, directly visualise SC and nn roots, no radiation exposure
• DISADVANTAGES: cost, limited availability, poorer spatial resolution than CT (may get significant slice thickness artefacts in small dogs and cats)


Aim - medical tx of IVDD in dogs

AIM: compressive material dissipates and the dorsal annulus heals over so more NP material does not herniate.


Outline medical tx of IVDD in dogs

- Strict cage rest (most important part), minimum 6 weeks (annulus repair),
- NSAIDs or narcotic analgesics for first 3-5 days if strict confinement likely to be enforced
- Mm relaxants (Methocarbamol) to decrease painful mm spasms
- GCs (prednisolone): many vets tx with these to decrease pain for first few days, no evidence to support long-term outcome, high risk of GIT side effects even with low doses. Never with NSAIDs. Not for acute spinal cord injury.
- Evaluate frequently for deterioration in neurologic status if tx medically
- Gentle physio + short lead walks (


What are the indications for medical tx of IVDD?

- single episode of pain + normal neurologic exam
- mild rear limb neuro deficits but dog still able to rise and walk unassisted.
- failure to improve within 5-7 days or neurological deterioration should prompt recommendation for sx intervention.
- Dogs with thoracolumbar disk extrusions rarely have uncontrollable pain or recurrent episodes of pain, but  sx.


Tx - thoracolumbar disc extrusions?

Most dogs recover from an episode of disk-related thoracolumbar pain with strict medical tx


Disadvantages - conservative management of IVDD

a higher rate of recurrence of CS and a higher chance of deterioration or persistent neurological deficits.


Indivations - sx tx of IVDD

- when decompression will significantly increase likelihood and completeness of recovery
- intractable or recurrent pain
- neurologic deficits +/- pain.
- All patients unable to walk at presentation.
- All dogs with signs suggesting less severe SC compression (paresis, pain) if neurologic signs don’t rapidly resolve with medical tx.
- Dogs which have lost pain sensation are a surgical emergency and are extremely unlikely to respond to conservative management.


Pros - sx tx of IVDD in dogs - 2

rate of recovery faster after decompression than non-sx and likelihood of residual neurologic deficits is decreased.


Define laminectomy

remove dorsal lamina of vertebral canal


Method of decompression for IVDD

decompression usually via a hemilaminectomy and extruded disk material is removed from spinal canal. Technically difficult – specialised equipment and training. Many surgeons also recommend concurrent fenestration of affected site and adjacent high risk sites to help decrease likelihood of subsequent herniations. In a fenestration - the NPs are removed through a small window created in the AF. This is a prophylactic procedure limiting further disc extrusions.


Post sx (IVDD - hemilaminectomy)- recommendations

keep calm and confined, padded bedding, frequent turning, manual bladder expression (min 4 times a day) an indwelling catheter or intermittent aseptic catheterisation. Swimming after skin incision healed. Paraplegic cart can provide stimulus for recovery.


Prognosis - IVDD post-surgery versus medical tx

Improvement in neuro fxn usually within 1 week. No improvement after 21d suggests poor prognosis. - Excluding loss of deep pain sensation, both conservative and sx tx have good prognoses (>80% for medical, generally >95% with surgery). Time to recovery is faster with surgery (because you are rapidly decompressing the SC).


What are the prognoses for IVDD with surgical intervention when considering absence/presence of deep pain sensation

o Deep pain sensation intact >90% dogs will improve
o Loss of deep pain for 48 hours - little chance of improvement


Why can't you localise a lesion to C1-C5 or C6-T2 in horses and instead say C1-T2?

some reflexes aren't testable in the horse - e.g. patella reflex thus LMN reflexes can't be differentiated in horses.


T/F: Trauma exacerbating an underlying CVM/S is quite common.



What is Ryegrass staggers?

(occasionally UK, warmer and damper climates – NZ, fungus which infects ryegrass)


What does CVM/S stand for?

cervical vertebral stenotic myelopathy


What is CVM/S?

- osseous compression of SC in neck, might be exacerbated by trauma
- often fast growing TB colts
- Associated with OCD and developmental defects and stenosis of spinal canal
- Dynamic (type 1) or static (type 2)
- Wallerian degeneration in ascending and descending tracts


Dx - CVM/S

- CS
- standing lateral (and oblique) radiographs
- myelography
- advanced testing


Outline dynamic stenosis (CVM type 1)

- When the neck is flexed or hyperextended, the vertebrae move excessively causing cord compression.
- Exacerbated by trauma
- Commonly affects C3-C5, and seen most frequently in young animals (fast-growing TB colts)
- Often worse with flexion (C3-C5) & extension (C5-C7)


Outline absolute stenosis (CVM type 2)

- Static = compression all of the time
• osseous changes in the vertebrae that cause spinal cord compression
• usually affects older horses at C5-C7
• Osteoarthritic changes in the articular process joints (facets) as a result of congenital OCD? other malformed vertebrae


What xrays are required for diagnosis of CVM/S?

Standing lateral (and oblique) radiographs of the spine are required for diagnosis.
• Take 3 xrays over different parts of neck, vertebrae lie just dorsal to jugular furrow
• 2 transverse processes must be overlying each other = good quality image


What are classic radiographic abnormalities of CVM/S?

- Caudal epiphyseal flare = ski ramping (on cd aspect of vertebral canal)
- Caudal extension of the dorsal vertebral lamina (when extends too far caudally, is associated with this problem)
- Step formation (where SC sits on a step of bone)
- Subluxation (thus SC more likely to get damaged)


What are oblique neck radiographs useful for?

- Helpful to ID fractures of articular processes
- Key element of objective assessment is inter- and intra-vertebral ratios


What are subjective radiographic signs of CVM/S? 3

• Spinal cord mal-alignment
• Osteoarthritis of articular processes
• Caudal epiphyseal flare aka ski-ramping (a triangle of new bone into the spinal canal)


Are intra- or intervertebral ratios more clinically useful?

- intra-vertebral measurements
- If this is


Describe the intervertebral ratio

Caudal aspect of the dorsal lamina of the vertebral arch of the more cranial vertebra to the dorsocranial aspect of the body of the more caudal vertebra, OR from the caudal vertebral body of the more cranial vertebra to the cranial dorsal lamina of the vertebral arch of the more caudal vertebra, whichever is smaller"


What is combined fluoroscopy and digital radiography used for?

to image down to C7 in standing horse (not possible with CT/ MRI)


What is the gold-standard ante-mortem diagnositc procedure to determine location of spinal cord compression?



Outline CSF in CVM/S

- CSF usually normal, may r/o other causes of ataxia.
- Usually lumbosacral collection
- Not routine if you consider wobbler syndrome
- You would do this if you suspected EHV-1  increased protein then increased cellularity (increased WBC – a pleiocytosis)


What is epiduroscopy?

endoscope placed b/w dura mater and pia mater (i.e. in space of arachnoid mater).


What is articular process joint ultrasound used for?

often not helpful, guidance for joint medication


Aetiology - CVM/S

• Role of genetics is still unclear - likely specific genes represent risk factors for disease development. These may need to be combined with acquired risk factors for disease to occur.
• A high plane of nutrition - contributor
• abnormal biomechanical forces through the limbs - contributor
• rapid growth – contributor.  narrowed spinal canal, or a canal that is narrowed upon movement of the neck  compresses SC leading to the deficits seen.


Tx - CVM/S

1. Pace diet (low carb, low protein)
2. Articular process joint medication/ ultrasound: standing sedated horse, inject corticosteroid (not useful for ataxic horses, useful in horses with neck pain)
3. Ventral stabilisation sx (vertebrae are locked together with implants in neck, look stiff but not painful)


Safety advice for a horse with CVM/S

Depends on severity, owner experience, use of the horse (hacking safer than dressage movements). Also how certain can you be of your diagnosis? Grade 2 ataxic + no riding. Gram 1 ataxic and less  ride at own risk. (remember grading scale is 0-5).


Outline the ataxia grading system

- GRADE 0 = no gait deficits at walk
- GRADE 1 = no gait deficits identified at walk, only during further testing
- GRADE 2 = deficits noted at walk
- GRADE 3 - marked deficits noted at the walk
- GRADE 4 = severe deficits noted at the walk may fall or nearly fall at normal gaits
- GRADE 5 (recumbent)