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

We report preliminary findings of nerve ultrasound in patients with cerebellar ataxia neuropathy vestibular areflexia syndrome ( C ANVAS) 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.