Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS): a review of the clinical features and video‐oculographic diagnosis

The association of bilateral vestibulopathy with cerebellar ataxia was first reported in 1991 and delineated as a distinct syndrome with a characteristic and measurable clinical sign--an absent visually enhanced vestibulo-ocular reflex--in 2004. We reviewed 27 patients with this syndrome and show that a non-length-dependent sensory deficit with absent sensory nerve action potentials is an integral component of this syndrome, which we now call "cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome" (CANVAS). All patients had brain MRI and 22/27 had evidence of cerebellar atrophy involving anterior and dorsal vermis, as well as the hemispheric crus I. Brain and temporal bone pathology in one patient showed marked loss of Purkinje cells and of vestibular, trigeminal, and facial ganglion cells, but not of spiral ganglion cells. There are two sets of sibling pairs, suggesting CANVAS is a late-onset recessive disorder. The characteristic clinical sign-the visual vestibulo-ocular reflex deficit-can be demonstrated and measured clinically using video-oculography.