Szmulewicz et al outlined criteria for the diagnosis of cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS). These can help to differentiate it from other disorders with ataxia. The authors are from Royal Victorian Eye & Ear Hospital (Melbourne), St. Vincent's Hospital (Melbourne), Alfred Hospital, University of Sydney, Monash University and Royal Prince Alfred Hospital in Australia.
Key diagnostic features:
(1) a hereditary disorder
(2) degeneration of the cerebellum with atrophy and ataxia. Examination of the cerebellum shows atrophy of the anterior and dorsal vermis and atrophy of the lateral hemispheres. Microscopically there is neuronal loss in the Purkinje cell layer.
(3) ganglionopathy affecting the dorsal root ganglia neurons with loss of myelinated neurons in the posterior columns of the spinal cord. Nerve conduction studies are abnormal with abnormal sensory nerve action potentials in a least one upper and one lower extremity nerve.
(4) bilateral vestibular neuronopathy (ganglionopathy) with bilateral vestibular hypofunction and an abnormal visually enhanced vestibular-ocular reflex (VVOR)
(5) exclusion of alternative diagnoses
In addition to cerebellar, vestibular and sensory deficits the patient may develop dysphagia, cough, autonomic dysfunction, allodynia and dysesthesia.
Differential diagnosis:
(1) Friedreich ataxia
(2) spinocerebellar ataxia
(3) multiple system atrophy with predominant cerebellar ataxia
(4) idiopathic cerebellar ataxia with bilateral vestibulopathy (iCABV)
(5) Wernick encephalopathy
Various findings allow for diagnosis as pathologically definite, clinically definite, clinically probable and clinically possible.
