Prevalence and Heritability of Symptomatic Syringomyelia in Cavalier King Charles Spaniels and Long‐term Outcome in Symptomatic and Asymptomatic Littermates

Abstract

BackgroundSyringomyelia (SM) is common in the Cavalier King Charles Spaniel (CKCS). Dogs with syringes express clinical signs or might be clinically silent.ObjectivesTo investigate the prevalence and heritability of symptomatic SM, the association between clinical signs and magnetic resonance imaging (MRI) findings, and long‐term outcome.AnimalsAll CKCS registered in the Danish Kennel Club in 2001 (n = 240).MethodsA cross‐sectional questionnaire‐based prevalence study validated by telephone interviews and clinically investigated clinical signs of SM. Dogs were 6 years at the time of investigation. A prospective observational litter study including clinical investigations, MRI and 5‐year follow‐up of symptomatic and asymptomatic siblings. Heritability was estimated based on the scale of liability in the study population and litter cohort.ResultsThe cross‐sectional study estimated a prevalence of symptomatic SM at 15.4% in the population. Thirteen symptomatic and 9 asymptomatic siblings participated in the litter study. Spinal cord syringes were confirmed in 21 of 22 littermates (95%). Syrinx diameter and mean syrinx : spinal cord ratio were significantly correlated with clinical signs (P < .01). Estimated heritability of symptomatic SM was 0.81. Symptomatic SM motivated euthanasia in 20%. Dogs with syringes, which expressed no clinical signs at the age of 6, remained asymptomatic in 14/15 cases (93%).Conclusions and Clinical ImportanceThe prevalence of symptomatic SM is high and genetics have a high impact on clinical disease expression. Further investigations of factors influencing the outbreak threshold of clinical signs of SM are desirable.

Investigation of sensory thresholds in Cavalier King Charles Spaniels with and without Chiari‐like malformations and syringomyelia

“…Lastly, we recognize that hyperesthesia could have been caused by coat clipping before thermal testing in some dogs, potentially increasing variability in thermal latencies. Although this lack of association is contrary to previous studies demonstrating a strong relationship between SM and pain,1, 11, 36, 37 there have been reports of asymptomatic CKCS with SM and CKCS displaying classical clinical signs without SM 8, 20, 38, 39. In our study, we had 7 symptomatic dogs without SM and 8 asymptomatic dogs with SM.…”

Dogs attending primary‐care practice in England with clinical signs suggestive of Chiari‐like malformation/syringomyelia

“…The main breeds identified as affected by symptomatic CM/SM in the current study align with those reported in the literature with brachycephalic and miniature breeds being predisposed (Thofner and others 2015). Risk factor analysis revealed that CKCS, KCS, Pomeranian, Chihuahua and Affenpinscher had increased odds of diagnosis of symptomatic CM/SM compared with crossbreds.…”

“…The period prevalence of symptomatic CM/SM in CKCS aligns with the results of Summers and others (2015), who reported symptomatic CM/SM in 1.7 per cent of CKCS in primary-care practice. Although a recent study of CKCS reported 15 per cent prevalence for symptomatic CM/SM in Denmark (Thofner and others 2015), the age range it focused on was restricted to dogs aged over six years, whereas the current study included dogs of all ages. However, responder bias in the Danish study could have resulted from some over-reporting of the condition because respondents were asked to volunteer their time to fill-in the questionnaire and it can be assumed that owners with experience and awareness of CM/SM would be more inclined to participate in this kind of study (Thofner and others 2015).…”

“…Although a recent study of CKCS reported 15 per cent prevalence for symptomatic CM/SM in Denmark (Thofner and others 2015), the age range it focused on was restricted to dogs aged over six years, whereas the current study included dogs of all ages. However, responder bias in the Danish study could have resulted from some over-reporting of the condition because respondents were asked to volunteer their time to fill-in the questionnaire and it can be assumed that owners with experience and awareness of CM/SM would be more inclined to participate in this kind of study (Thofner and others 2015). Other reports on CM/SM prevalence originate mainly from investigations relying, for definitive diagnosis, on MRI (Parker and others 2011, Thofner and others 2015) among all cases (symptomatic and asymptomatic) rather than records of clinically affected animals from primary-care practice, which are the dogs that have compromised welfare.…”

Questionnaire‐based Analysis of Owner‐reported Scratching and Pain Signs in Cavalier King Charles Spaniels Screened for Chiari‐like Malformation and Syringomyelia

“…Cavalier King Charles Spaniels (CKCS) have an extremely high prevalence of Chiari‐like malformations (CM) and syringomyelia (SM) . Chiari‐like malformation results in a brain and skull mismatch that produces a relatively small caudal fossa with crowding of the foramen magnum, and stenosis of cranial venous sinuses and skull foraminae .…”