Cerebellar ataxia syndrome with neuropathy and vestibular areflexia (CANVAS) is a genetic pathology of recent discovery (bi-allelic expansion in intron 1 of the RFC1 gene with AAGG repetition). The clinical picture is protean, associating a neuronopathy, a bilateral vestibulopathy evidenced by an alteration of the oculovestibular reflex (VOR), an atrophy of the cerebellum and a chronic cough.

In the initial stage of the disease the clinical picture is heterogeneous and often incomplete. Ataxia at the beginning of the disease may be the consequence of peripheral nervous system involvement (neuronopathy) and the cerebellar syndrome may manifest itself clinically late.

Eye movement involvement in central nervous system pathologies is common (4). Oculomotor abnormalities are often subclinical and sometimes exclusively identifiable by an instrumental study, video-oculography (VOG) (5).

VOG is a non-invasive examination of eye movements, which is increasingly used in the differential diagnosis of neurodegenerative syndromes (6). This examination allows, among other things, to identify oculomotor anomalies, even discrete and asymptomatic, by studying the combined movements of the eyes and the oculocephalic movements.

The study of oculomotricity by VOG can therefore potentially contribute to the early differential diagnosis of ataxiating neuropathies, including CANVAS, by revealing infra-clinical oculomotor abnormalities correlated with a cerebellar expectation (knowing the role of the dorsal vermis in the precision of saccades and pursuits).

Inclusion Criteria:

Patients followed at the University Hospital of Nîmes between 2018-2021

• Age > 18 years
• Patients with CANVAS with genetic confirmation (RFC1 gene mutation)
• Patients with axonal neuropathy, autoimmune neuronopathy and anti-MAG neuropathy
• Healthy controls

Patients followed at the CHU of Nîmes between 2018-2021, with a diagnosis of CANVAS with several control groups constituted by patients with a neuropathy of different etiology (a first control group with axonal neuropathies and thus no ataxia in the foreground, a second group with ataxiating neuropathies : (anti-MAG neuropathy, neuronopathies of autoimmune origin) and a healthy control group without neuropathy).