CANVAS (Cerebellar Ataxia, Neuropathy, and Vestibular Areflexia Syndrome) Video Head Impulse Test (vHIT) Figure

CANVAS (Cerebellar Ataxia, Neuropathy, and Vestibular Areflexia Syndrome) is a genetic condition consisting of slowly progressive late-onset ataxia, bilateral vestibulopathy, sensory neuropathy, chronic cough, and autonomic dysfunction. While the term vestibular areflexia typically implies bilateral vestibular loss, these patients may have varying degrees of vestibulopathy depending on their stage of disease. Herein, we present three patients with RFC1+ CANVAS demonstrating the heterogeneity of vestibular impairment. Prior to the recent identification of the RFC1 gene expansion in CANVAS, patients A. (mild unilateral vestibulopathy) and B. (mild bilateral vestibulopathy) probably would not have been diagnosed with CANVAS. However, it is likely that vestibular loss and vHITs in patients A. and B. will eventually resemble that of patient C. (severe bilateral vestibulopathy). Video head impulse test (vHIT) findings in three patients with clinical CANVAS syndrome and confirmed biallelic RFC1 gene expansion (A.) A 70-year-old patient (sibling of patient B.) with a 30-year history of chronic cough, a 25-year history of progressive sensory neuropathy, and a 3-year history of dizziness time-locked to head movements. Overt saccades (corrective saccades occurring after the head movement - arrows) are seen mainly in the planes of the right horizontal (lateral) and posterior canals, suggestive of a mild right vestibulopathy. Gains horizontally were slightly higher than 1, likely due to calibration error or goggle slippage, and abnormally low (<0.7) in the plane of the right posterior canal. (B.) A 63-year-old patient (sibling of patient A.) with a 32-year history of chronic cough and a 10-year history of progressive imbalance and incoordination. Gains are abnormally low in the planes of the left anterior canal and bilateral posterior canals, and low-normal (~0.7) with clear overt corrective saccades in the planes of the horizontal canals, suggestive of mild bilateral vestibulopathy. (C.) A 76-year-old patient (no relation to patients A. or B.) with a 20-year history of progressive imbalance (now requiring a walker to mobilize), peripheral sensory loss and chronic cough. Significantly reduced gains are seen in the planes of all 6 semicircular canals with associated bilateral overt saccades, consistent with severe bilateral vestibulopathy.