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