Dorsal root ganglionopathy is responsible for the sensory impairment in CANVAS

Objective: 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. Method: Brain and spinal neuropathology in 2 patients with CANVAS, together with brain and otopathology in another patient with CANVAS, were examined postmortem. Results: Spinal cord pathology demonstrated a marked dorsal root ganglionopathy with secondary tract degeneration. Cerebellar pathology showed loss of Purkinje cells, predominantly in the vermis. Conclusion: 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.