Objective: We aim to present the cerebellar cognitive affective evaluation and phenotypic description of a series of genetically confirmed CANVAS.

Background: Cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS) presents in middle life as a slowly progressive ataxia, a sensory neuropathy and a bilaterally impaired vestibulo-ocular reflex. Diagnosis is based on clinical findings, recently supported by genetic testing of biallelic AAGGG repeat expansions in the replication factor complex subunit 1 (RFC1). To our knowledge, cerebellar cognitive function has not yet been studied in CANVAS patients. We present a detailed phenotypic description of a series of 9 genetically confirmed CANVAS, including neuropsychological testing.

Method: We have retrospectively collected data to describe symptoms, physical examination, family history, neuropsychological evaluation, other complementary tests and natural history.

Results: All patients are Caucasian, predominantly male (6:3). The median age of symptom onset, excluding cough, is 55. All patients (n=9) present biallelic repeat expansions in RFC1, 3 patients deny family history. All patients present ataxia with instability and broad-based gait, some also present dysmetria, dysphagia or altered proprioception. Most patients show hypoesthesia, hypopalesthesia or paresthesia. Many patients present vestibulo-ocular reflex hypofunction. The most notable associated symptoms are chronic cough, found in all patients, and altered osteotendinous reflexes (areflexia in 5 patients, hyporeflexia in 2 patients, hyperreflexia in 1 patient). All patients underwent neuropsychological evaluation using the cerebellar cognitive affective/Schmahmann syndrome scale. The main radiologic finding is mild cerebellar atrophy in 7 patients. 6 patients underwent electroneurography, all of which present sensory axonal polyneuropathy. Patients require walking aids after a median of 8 years.

Conclusion: We must include CANVAS in our differential diagnosis for late onset ataxia and sensory neuropathy, since RFC1 amplification is very likely to be underdiagnosed as it has been described recently. A detailed examination of CANVAS patients may include a cerebellar cognitive evaluation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neuropsychological-evaluation-of-cerebellar-cognitive-function-in-a-series-of-patients-with-genetically-confirmed-canvas/