Syringomyelia in Australian Cavalier King Charles spaniels: prevalence and changes over 16 years of magnetic resonance imaging screening

Syringomyelia is a common and heritable disorder in Cavalier King Charles Spaniels (CKCS), characterised by fluid accumulation within the spinal cord that may result in pain and neurological dysfunction. The prevalence of syringomyelia in CKCS in Australia has not previously been reported. The goal of this study was to assess the prevalence and severity of syringomyelia in magnetic resonance imaging (MRI)-screened breeding CKCS in New South Wales, Australia, from 2008 to 2024, and to evaluate changes over time. A secondary goal was to investigate associations between age and coat colour with the prevalence and severity of syringomyelia. A retrospective observational study was conducted on 386 CKCS undergoing voluntary MRI screening. The dogs included in the study had no clinical signs of syringomyelia or Chiari-like malformation. Syringomyelia was defined as fluid accumulation within the spinal cord with a diameter ≥ 1.0 mm. Dogs were graded by severity and grouped by age, coat color and screening period. Statistical analyses included Fisher's exact test, Wilcoxon rank-sum, Kruskal-Wallis and multivariable logistic regression. Syringomyelia was detected in 50.5% of dogs. No significant change in prevalence or severity was observed over the 16-year period. Syringomyelia prevalence increased with age (P < 0.001). Coat colour was associated with both prevalence and severity, with black and tan dogs more severely affected than Blenheim dogs (P = 0.007). Syringomyelia was highly prevalent in Australian CKCS, with no significant improvement over time despite voluntary screening and breeding recommendations. Greater emphasis on MRI screening beyond 3 years of age and stricter breeding practices may be necessary to reduce disease prevalence and severity in the breed.