Dorsal root ganglionopathy is responsible for the sensory impairment in CANVAS

To elucidate the neuropathology in cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS), a novel cerebellar ataxia comprised of the triad of cerebellar impairment, bilateral vestibular hypofunction, and a peripheral sensory deficit.

Brain and spinal neuropathology in 2 patients with CANVAS, together with brain and otopathology in another patient with CANVAS, were examined postmortem.

Spinal cord pathology demonstrated a marked dorsal root ganglionopathy with secondary tract degeneration. Cerebellar pathology showed loss of Purkinje cells, predominantly in the vermis.

The likely underlying sensory pathology in CANVAS is loss of neurons from the dorsal root and V, VII, and VIII cranial nerve ganglia-in other words, it is a "neuronopathy" rather than a "neuropathy." Clinically, CANVAS is a differential diagnosis for both spinocerebellar ataxia type 3 (or Machado-Joseph disease) and Friedreich ataxia. In addition, there are 6 sets of sibling pairs, implying that CANVAS is likely to be a late-onset recessive or autosomal dominant with reduced penetrance disorder, and identification of the culprit gene is currently a target of investigation.