Degree of Inflammation in Surgically Obtained Intervertebral Disc Extrusions in a Population of 74 Dogs.

Intervertebral disc disease remains the most common spinal pathology in dogs and is characterized by degeneration of the intervertebral disc, primarily through chondroid metaplasia of the nucleus pulposus. Current histological grading systems for disc degeneration do not include inflammation, despite its potential relevance in clinical presentation through extradural swelling and compression. In this retrospective study, surgically removed disc extrusion material from 74 dogs was histologically processed and evaluated using a semi-quantitative grading system for disc degeneration and inflammation. A high prevalence of chondroid metaplasia was observed, frequently accompanied by inflammatory infiltrates, hemorrhage, and necrosis. A significant positive correlation (correlation coefficient = 0.636, p < 0.001) was found between the degree of degeneration and the intensity of inflammation. Notably, thoracolumbar extrusions exhibited significantly higher inflammatory scores than cervical cases. In Dachshunds, more severe neurological deficits were associated with lower histological degeneration scores, indicating that neurological severity depends on multiple interacting factors that may differ between breeds. No significant associations were identified with age, sex, breed, body weight, neurological localization, or lesion severity in other groups. These findings suggest that inflammation is an active component in the pathophysiology of intervertebral disc disease. Incorporating inflammatory grading into histological grading systems could refine functional outcome predictions and guide therapeutic decisions.