Intervertebral disk degeneration
- Associated with loss of water from the nucleus pulposus due to lowering of proteoglycan content
- Reduces the cushioning function
- Can lead to herniation of the nucleus pulposus through the annular rings and impinge on the spinal cord.
- Breeds
- Dachshund (45-75% of cases), Pekingese, beagle, Lhaso apso and cocker spaniel
- Probably partly because all are chondrodysplastic to a varying degree
- Occurs in all disks simultaneously (cf: non chondrodysplastic dogs – degeneration in only one disk at a time).
- Chondrodysplastic dogs -> chondroid metaplasia of the nucleus pulposus, with progressive calcification
- Occurs at a young age … cf non-chondrodysplastic breeds , occurs as a senile change
- Progressive decrease in amount of glycosaminoglycans, and changes from chondroitin sulphate to keratin sulphate over the first few years of life
- Hansen type I protrusions – explosive and large
- Non-chondrodysplastic dogs -> progressive fibrous metaplasia of the nucleaus pulposus, starting at the periphery
- Increased amount of type I collagen (poor at withstanding compressive loads)
- Can lead with time, to bulging of the remaining nucleus pulposus dorsally, as it becomes increasingly constricted by the annular fibrosa
- Calcification is uncommon
- Hansen type II protrusions -> small and progressive