The prevalence of intervertebral disc degeneration in the cervical, thoracic, and lumbar spine in asymptomatic cats

OBJECTIVE: To investigate the prevalence and severity of intervertebral disc (IVD) degeneration (IVDD) throughout the spine of young, middle-aged, and old asymptomatic cats; identify differences between the cervical, thoracic, and lumbar spine; and investigate the influence of sex and neuter status on the prevalence of feline IVDD. METHODS: 60 cadavers were collected from asymptomatic cats and subdivided into 3 age groups: young (≥ 1 to < 6 years), middle aged (≥ 6 to < 12 years), and old (≥ 12 years). T2 weighted sagittal MRI studies of the spine were obtained. Each IVD was graded according to the modified Pfirrmann grading for feline IVDD. Cumulative link mixed models were used to analyze the significance of spinal region, age, sex, and neuter status on the degenerative state of the IVDs. RESULTS: A total of 1,544 IVDs were evaluated; 884 (57.3%), 425 (27.5%), 147 (9.5%), 82 (5.3%), and 6 (0.4%) were graded Pfirrmann 1, 2, 3, 4, and 5, respectively. Irrespective of spinal region, middle-aged cats (OR, 4.03; P < .01) and old cats (OR, 12.5; P < .01) had significantly higher odds for IVDD compared to young cats. For old cats, thoracic (OR, 4.44; P < .01) and cervical IVDs (OR, 2.76; P < .01) had significantly higher odds of degenerating compared to lumbar IVDs. No significant effect of sex (P = .81) and neuter status (P = .61) was found. CLINICAL RELEVANCE: The prevalence of feline IVDD significantly increases with progressive age, with the thoracic and cervical IVDs showing the highest odds for degeneration. However, extreme stages of IVDD were only occasionally observed.