Nerve ultrasound in CANVAS‐spectrum disease: Reduced nerve size distinguishes genetically confirmed CANVAS from other axonal polyneuropathies

Ultrasound nerve cross‐sectional area (CSA) of patients affected with axonal neuropathy usually shows normal value. Cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS) seems to represent an exception, showing smaller CSA, but previous reports did not test for biallelic RFC1 gene repeat expansions.