Peripheral nerve ultrasound in cerebellar ataxia neuropathy vestibular areflexia syndrome (CANVAS).

INTRODUCTION: We report preliminary findings of nerve ultrasound in patients with cerebellar ataxia neuropathy vestibular areflexia syndrome (CANVAS) who have sensory impairment due to dorsal root ganglionopathy.

METHODS: The ultrasound cross-sectional area (CSA) of median and ulnar nerves of 7 CANVAS patients was compared with 7 age- and gender-matched controls and with the mean CSA of our reference population.

RESULTS: The nerve CSA of CANVAS patients was significantly smaller than that of controls at all sites (P < 0.01). All but 1 individual measurement of CSA at the mid-forearm level in the CANVAS patients fell outside the normal control range and was >2 standard deviations below the reference mean.

CONCLUSIONS: The small nerves in CANVAS probably reflect nerve thinning from axonal loss secondary to ganglion cell loss. Our data show a role for ultrasound in the diagnosis of CANVAS ganglionopathy. This may also be applicable to ganglionopathy from other causes. Muscle Nerve 56: 160-162, 2017.