F33. Cross sectional peripheral nerve area in canvas syndrome (cerebellar ataxia neuropathy vestibular areflexia syndrome)

Abstract

Introduction Patients with Cerebellar Ataxia Neuropathy Vestibular Areflexia Syndrome (CANVAS) have sensory impairment due to dorsal root ganglionopathy. After preliminary findings of small nerves on ultrasound in CANVAS, we sought to systematically study a larger cohort of CANVAS patients to see if this is a feature of this ganglionopathy and thus distinct from the ultrasound findings in axonal neuropathy. Methods The ultrasound cross sectional area (CSA) of median and ulnar nerves of 14 CANVAS patients was compared with 14 age- and gender-matched healthy controls (HCONT) and 14 age-and gender-matched patients with acquired axonal neuropathy (PNCONT). The individual CSAs of CANVAS and PNCONT patients were also compared with the mean CSA of our reference population. Results The nerve CSA of CANVAS patients was significantly smaller than the CSA of both HCONT and PNCONT at all sites ( P > 2 SDs below a reference mean. Conclusion The small nerves in CANVAS probably reflect nerve thinning from axonal loss secondary to ganglion cell loss. This is in contradistinction to the ultrasound abnormality in PNCONT, in which the nerves are mildly enlarged. Our data show a role for ultrasound in the diagnosis of CANVAS ganglionopathy. This may also be applicable to sensory neuronopathy from other causes.