Behavioral and clinical signs of Chiari-like malformation-associated pain and syringomyelia in Cavalier King Charles spaniels

Abstract

Background: Diagnosis of Chiari-like malformation-associated pain (CM-P) or clinically relevant syringomyelia (SM) is challenging. We sought to determine common signs. Animals: One hundred thirty client-owned Cavalier King Charles spaniels with neuroaxis magnetic resonance imaging (MRI) and diagnosis of CM-P/SM. Dogs with comorbidities causing similar signs were excluded with exception of otitis media with effusion (OME). Methods: Retrospective study of medical records relating signalment, signs, and MRI findings. Dogs were grouped by SM maximum transverse diameter (1 = no SM; 2 = 0.5-1.99 mm; 3 = 2-3.9 mm: 4 = ≥4 mm). Differences between all groups—groups 1 versus 2-4 and groups 1-3 versus 4—were investigated. Continuous variables were analyzed using 2-sample t-tests and analysis of variance. Associations between categorical variables were analyzed using Fisher's exact or chi-square tests. Results: Common signs were vocalization (65.4%), spinal pain (54.6%), reduced activity (37.7%), reduced stairs/jumping ability (35.4%), touch aversion (30.0%), altered emotional state (28.5%), and sleep disturbance (22%). Head scratching/rubbing (28.5%) was inversely associated with syrinx size (P =.005), less common in group 4 (P =.003), and not associated with OME (P =.977). Phantom scratching, scoliosis, weakness, and postural deficits were only seen in group 4 (SM ≥4 mm; P =.004). Conclusions and Clinical Importance: Signs of pain are common in CM/SM but are not SM-dependent, suggesting (not proving) CM-P causality. Wide (≥4 mm) SM is associated with signs of myelopathy and, if the dorsal horn is involved, phantom scratching (ipsilateral) and torticollis (shoulder deviated ipsilateral; head tilt contralateral).