Background Sensory ganglionopathy is typified by selective peripheral sensory axonal loss on nerve conduction studies (NCS) and can occur with CANVAS (cerebellar ataxia with neuropathy and bilateral vestibular areflexia) syndrome.

Case: A 53-year old woman had a 4-year history of some unsteadiness, slurred speech and distal sensory symptoms. She also reported a daily cough over the past 10 years. Clinically, she had dysarthria and mild sensory ataxia. Proprioception and deep tendon reflexes were preserved.

Results of Investigations: NCS demonstrated markedly reduced sensory nerve action potential (SNAP) amplitudes in upper and lower limbs with normal motor NCS. The tibial H-reflexes were strikingly retained. Genetic testing confirmed biallelic RFC1 intronic repeat expansion mutation consistent with CANVAS syndrome.

Discussion The retained H-reflexes (and tendon reflexes) indicates relative sparing of the group Ia muscle afferents that originate from muscle spindle primary endings and are known to contribute significantly to proprioception. This accounts for the relatively mild gait ataxia in the setting of CANVAS syndrome despite marked sensory NCS abnormalities.