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 midforearm 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.