Pathology, Diagnosis and Treatment of Vertebral Column Diseases Flashcards
What is the most common cause of paresis/ paraplegia in dogs?
Disc Degeneration
- Loss of Glycosaminoglycans, means less water is retained in the disc, loss of cushion function, and further damage –> Disc protrusion/ displacement
What is the pathophysiology of IVD degeneration?
1) Trauma or Chronic loading/ abnormal biomechanical stress or genetic predisposition
2) Matrix remodeling to disc
3) Loss of GAG, Increase in Collagen
4) Matrix dehydration
5) Structural and functional failure of matrix
6) Further disc damage leading to prolapse, herniation, annular tears etc.
Disc degeneration in dogs can be divided into 2 groups, what are they?
Chondrodystrophic breeds: Dachsund, Basset hound, French + English bulldog, Shi Tzu, Pekingese, Corgi, etc.
Non-Chondrodystrophic breeds
We have done this because they differ in age of onset, frequency, and spinal location of the disc degeneration
Why is disc degeneration more common in Chondrodystrophic breeds?
(Dachsund, Basset hound, French + English bulldog, Shi Tzu, Pekingese, Corgi, etc.)
They have disturbed endochondral ossification of the long bones, and thus short limbs
They also have smaller nucleus pulposus in their intervertebral discs, which is also located more dorsally
(Bad legs, bad discs)
What is the genetic cause of early disc degeneration in Chondrodystrophic breeds?
They have an abnormal expression of a growth factor gene (FGF4), which is expressed in embryonic development that facilitates limb and notochord development
Two types of intervertebral disc disease are seen, Hansen type 1 and Hansen type 2 disc disease, what is the difference between them?
Type 1:
- typically an acute mechanical failure with rupture of the dorsal annulus fibrosus and extrusion of nucleus pulposus
- characterized by free disc material within the vertebral canal and may be explosive
- seen in chondrodystrophic breeds and typically between 2 and 7 years of age with the highest incidence at 4–6 years
- A Hansen type 1 IVDD is by definition a disc EXTRUSION
Type 2:
- often more chronic in nature and is characterized by a bulging of the dorsal annulus
- may occur in chondrodystrophic and non-chondrodystrophic breeds
- No free disc material occurs within the vertebral canal
- Hansen type 2 IVDD is, therefore, a disc PROTRUSION as opposed to a disc extrusion
What are the 2 disc degeneration types?
- Chondroid metaplasia
- Fibroid metaplasia
Both of which will result in changes to the biochemistry of the disc and therefore changes in properties
You are presented with a Chondrodystrophic breed, and you suspect disc degeneration, what type of degeneration will it have?
Chondroid metaplasia
- Starts b/w 8 months - 2 years
- 75% of discs show signs of degeneration by 1 year
- Decreased proteoglycans + water content
- Increased collagen content
- Calcification within the nucleus
- Decreased shock-absorbing ability
- Acute mechanical failure, with or without trauma
You are presented with a Non-chondrodystrophic breed, and you suspect disc degeneration, what type of degeneration will it have?
Fibroid metaplasia
- Slower onset
- Rarely calcified
- Nucleus maintains a more gel-like consistency
- Will see a bulging dorsal annulus
What is the layman’s term for Cervical Vertebral Stenotic Myelopathy?
Wobbler’s Syndrome
What is the proper term for Wobbler’s Syndrome?
Cervical Vertebral Stenotic Myelopathy
What species are affected by Cervical Vertebral Stenotic Myelopathy (Wobbler’s Syndrome)?
Horses
Dogs
What happens in Wobbler’s Syndrome that leads to its clinical signs/ presentation?
- Cervical vertebral malformation results in progressive spinal cord compression and injury, leading to ataxia and paresis (wobble)
What are the 2 theories behind why Wobbler’s Syndrome happens in horses?
1) Developmental: a disorder of bone/ cartilage development leading to cervical vertebral malformation
2) Biomechanical: abnormal mechanical stresses deform the cervical column resulting in stenosis of the canal
- The equine vertebrae growth plates are susceptible to biomechanical stresses until ~5 years old when they eventually close
In reality it’s probably a mix of both
When a horse develops Wobbler’s Syndrome, there are 2 possible manifestations of it, what are they?
1) Functional instability: this is a dynamic compression, where there is unstable articulation between C3-C5, leading to a narrowing of the canal during cervical ventroflexion (head down)
The spinal cord becomes compressed and blood vessels are pinched or ruptured
2) Static stenosis: Regardless of the head/ neck position, you get narrowing of the canal due to thickening of the dorsal laminae bone + hypertrophy of the ligamentum flavum
An 8 - 18 month old, fast-growing male Thoroughbred presents with Wobbler’s Syndrome, which manifestation is most likely in this case?
Functional Instability: dynamic compression leading to narrowing of the canal during cervical ventroflexion (head down)
What is the term used to describe intervertebral disc inflammation with inflammation of the adjacent vertebrae?
Discospondylitis
What are the causes of Discospondylitis in patients?
- Bacterial more common: Staph, Streps, E.coli
- Fungal: Candida and Aspergillus spp
How does an infection access the intervertebral discs and what might be the possible sources of infection?
- Hematogenous or lymphatic system: endocarditis, UTI’s, pyoderma, prostatitis, dental infections, which can travel through the vessels and allow microorganisms to penetrate the endplates to access the discs
- Migrating grass seeds/ awns/ ‘foxtails’ which carry bacteria: can be inhaled and migrate through the lungs to the diaphragm insertion on the lumbar spine, or can penetrate the skin and paravertebral musculature
What is the definition of Spondylosis Deformans?
Degeneration of vertebrae, leading to the formation of osteophytes, which are bony spurs or bridges around the disc and nearby spinal joints
Why does Spondylosis Deformans occur?
Likely triggered by changes in the annulus fibrosus, the tough outer ring of the intervertebral disc.
What is the Modified Frankel Grading Scale, and what are the 5 grades?
The Frankel Grade classification provides an assessment of spinal cord function and is used as a tool in spinal cord injury
Grade 1: Pain/ hyperaesthesia only, NO deficits
Grade 2: Ambulatory paraparesis/ tetraparesis (depending on the location of the lesion), usually with proprioceptive ataxia
Grade 3: Non-ambulatory paraparesis/ tetraparesis
Grade 4: Paraplegia/ Tetraplegia = paralyzed
Grade 5: Absent Nociception
You are presented with a dog that has IVDD, you want to perform a radiograph first, what can the radiograph help to rule in/out?
- Discospondylitis
- Congenital Vertebral Malformation
- Neoplasia
Caution: small lesions or early diseases may not show up on a radiograph
You perform a Modified Frankel Grading Scale on a dog that presents with spinal pain, you notice it has deficits (Grade 2+), how would you prefer to treat this dog?
- Surgical management preferably
You perform a Modified Frankel Grading Scale on a dog that presents with cervical spinal pain only (Grade 1), the owner reports this is the first time this has happened, how can you manage this dog?
- Medical management can be performed: rest, NSAIDs, Gabapentin, Tramadol
- Surgical management should be discussed to prevent worsening of the condition as the more chronic it is, the more difficult the surgery becomes
You perform a Modified Frankel Grading Scale on a dog that presents with cervical spinal pain only (Grade 1), the owner reports this has happened before, how would you prefer to manage this dog?
- Surgical management is ideal as there have been repeated episodes
You perform a Modified Frankel Grading Scale on a dog that presents with cervical spinal pain and neurologic deficits (Grade 2+), how would you prefer to manage this dog?
- Surgical management
You perform a Modified Frankel Grading Scale on a dog that presents with Thoracolumbar spinal pain and neurologic deficits (Grade 2+), how would you prefer to manage this dog?
- Surgical management
You are presented with a dog that has spinal pain, the Owner either elects for medical management only, or you feel medical management is necessary before surgery, what is included in the medical management of spinal pain/ disease?
1) Strict exercise restriction/ cage rest for a minimum of 4 - 6 weeks
2) Gradually increase exercise over the next month following
3) Use a harness ONLY, no neck leads
4) Drugs:
- NSAIDs (avoid steroids)
+ Tramadol (2-4 mg/kg BID-TID)
+ Gabapentin (10 mg/kg TID, or 15 mg/kg BID)
+/- Diazepam or methocarbamol
5) Acupuncture
6) Physical rehabilitation + neck massage
What is the most common surgical procedure used when treating IVDH (intervertebral disc herniation) in the cervical spine?
- Ventral Slot
What is the most common surgical procedure used when treating IVDH (intervertebral disc herniation) in the thoracolumbar spine?
- Hemilaminectomy
You grade a dog with Grade 1 - 4 on the Modified Frankel Grading Scale, and it undergoes surgery for Hansen Type I, what is the prognosis of neurologic recovery?
80 - 100%
You grade a dog with Grade 1 - 4 on the Modified Frankel Grading Scale, the owners elect for medical management only for Hansen type I, what is the prognosis of neurologic recovery?
Unpredictable
There is possible recovery but further deterioration is likely
You grade a dog with Grade 5 on the Modified Frankel Grading Scale, and it undergoes surgery, what is the prognosis of neurologic recovery?
50% if done under 48 hours
Prognosis gets worse as time goes on/ becomes chronic
What is the prognosis for a dog with Hansen Type II IVDH when comparing surgical to medical management?
Generally not as good as Hansen Type I (extrusion)
This is because of the more gradual progression and chronicity of the spinal cord compression with annulus fibrosis protrusion, leading to spinal cord atrophy and possibly irreversible axonal damage
Surgical management prognosis = 70%
Medical management prognosis = 30%
What are the 2 broad types of Wobbler’s Syndrome in dogs?
- Osseous-associated wobbler syndrome (OAWS)
- Disc-associated wobbler syndrome (DAWS)
These are based on what causes the compression of the cervical spinal cord/ nerve roots
What causes the compression involved in Osseous-associated wobbler syndrome (OAWS), and what breeds are predisposed?
- Compression caused by a combination of vertebral malformation and osteoarthritis, affecting the articular facet joint
+/- Disc protrusion (especially in older dogs)
+/- Ligamentous compression (ligamentum flavum hypertrophy) - giant-breed dogs
- Usually young adults
What causes the compression involved in Disc-associated wobbler syndrome (DAWS), and what breeds are predisposed?
- Compression is caused by intervertebral disc herniation (Hansen Type II)
- Large-breed dogs (common in Doberman Pinschers)
- Usually older/ geriatric
What is the medical treatment for Wobbler’s Syndrome in Dogs?
What is the Prognosis for medical management?
1) Exercise restriction
2) Harness walks
3) Drugs:
- NSAID’s or Steroids (prednisolone 0.5-1. mg/kg/day for 2-3 weeks): can help reduce cord edema associated with compression
- Gabapentin, Tramadol, Amantadine
Prognosis: 55% improvement. 25% no change
What is the surgical treatment for Wobbler’s Syndrome, specifically OAWS, in Dogs?
What is the prognosis for surgical management?
- Dorsal laminectomy most common
Trying to decompress the spinal cord
Prognosis: 80% improvement
What is the surgical treatment for Wobbler’s Syndrome, specifically DAWS, in Dogs?
What is the prognosis for surgical management?
- Ventral slot
- Distraction stabilization technique
Prognosis: 80% improvement
What is Cauda Equine Syndrome?
A collection of clinical signs relating to pathology at the level of the cauda equina and its adjacent nerve roots
Signs include:
- Pain!
- Hind end stiffness that leads to difficulty in walking, climbing stairs, getting on furniture, wagging the tail, positioning to defecate, or getting into a car
What is the most common cause of Cauda Equina Syndrome in dogs?
What are the other, less common, causes?
Most commonly:
- Degenerative lumbosacral stenosis, usually at the lumbosacral joint, leading to bony proliferation and/ or soft tissue proliferation/ hypertrophy and causing compression of the cauda equina/ nerve roots. This is multifactorial and a whole range of pathologies can be associated with this degeneration
Other causes:
- Intervertebral disc herniation
- Inflammation
- Infection
- Infiltrative
- Neoplastic
What is the medical treatment protocol for Cauda Equina Syndrome in dogs?
- Cage rest and exercise restriction, NSAIDs, Tramadol, Gabapentin, +/- amantadine
+/- Epidural steroid (1 mg/kg MPA at week 0, 2 and 6)
Note: there is a 55% success rate with NSAIDs +/- gabapentin and 4-6 weeks of restricted exercise
What is the surgical treatment protocol for Cauda Equina Syndrome in dogs?
- Dorsal laminectomy +/- dorsal annulectomy/ fenestration
What is the treatment for Discospondylitis?
1) Long term antimicrobials that will reach high concentration in the bone
- Ideally based on microbial culture and sensitivity (disc aspirate, urine or blood culture)
8 weeks of a first-generation cephalosporin e.g.:
- Cephalexin (20 mg/kg TID)
- Amoxicillin clavulanic acid (20 mg/kg BID-TID)
- TMPS (15 mg/kg BID)
2) NSAIDs + analgesics (tramadol + gabapentin) for the first 2 weeks of treatment
3) Surgery: stabilization of the affected vertebrae only if there is vertebral instability
