Investigation of Sensory Thresholds in Cavalier King Charles Spaniels with and without Chiari-like Malformations and Syringomyelia

Introduction: Ninety-two percent of Cavalier King Charles Spaniels (CKCS) have a skull malformation called Chiari-like malformation (CM). CM is frequently associated with syringomyelia (SM), an accumulation of fluid within the spinal cord that has been linked to a neuropathic pain syndrome. The purpose of this study was to obtain quantitative data on thermal and mechanical thresholds in CKCS with and without SM. We hypothesized that CKCS affected with SM will have lower sensory thresholds when compared with unaffected dogs.

Materials and Methods: Fifty-four dogs were classified as symptomatic or not by their owners, presence of pain was noted on neurological examination, sensory thresholds testing was performed, and SM was identified on magnetic resonance imaging.

Results: Owners reported 24/54 dogs as painful, 33/54 had scratching signs, 40/54 were painful on examination and 34/54 had SM. There was no significant difference in sensory thresholds between dogs with and without SM (p > 0.5). Owner-reported symptomatic dogs had lower mechanical thresholds on the paw (median: 0.367 kg) and neck (2.075 kg) compared with asymptomatic dogs (0.6275 kg and 2.545 kg, respectively) (p = 0.009 and 0.007, respectively). Dogs that exhibited pain on neurological examination had decreased latencies to heat at the thorax (median = 17.55 seconds) compared with dogs that were not painful (22.16 seconds) (p = 0.03). Mechanical thresholds were lower on the side of the neck that corresponded to lateralization of SM in dogs with asymmetrical syrinxes (p = 0.015, 0.09).

Discussion: This information can be leveraged to optimize treatment protocols and objectively study efficacy of future therapeutics in CKCS.

Acknowledgments: Research Grant: The American Cavalier King Charles Spaniel Club Charitable Trust through the American Kennel Club Canine Health Foundation. Student Support: AVMA/AVMF 2nd Opportunity Summer Research Scholarship; George H. Hitchings New Investigator Award in Health Research