Intervertebral Disc Degeneration

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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