CANVAS Patients :  Inclusion Criteria:  Patients followed at the University Hospital of Nîmes between 2018-2021 Age > 18 years Diagnosis of CANVAS with genetic evidence (RFC1+) Diagnosis of neuronopathy  Exclusion Criteria:  Age <18 years Chronic polyradiculoneuritis or other demyelinating neuropathy  Control group, inclusion criteria :  Patient with axonal sensory-motor or pure sensory neuropathy confirmed by electro neuromyography, and concordant with the clinic.