Vestibular impact of Friedreich ataxia in early onset patients.

Objective: Friedreich ataxia (FRDA) is the most frequent form of inherited ataxias. Vestibular and auditory assessment is not commonly part of the check up for these patients despite hearing and balance complaints. Screening of vestibular and auditory function was performed in a large group of young patients with genetically confirmed FRDA.
Methods: Our study included 43 patients (7-24 years of age). A complete vestibular assessment was performed including the canals function evaluation at 3 head velocities (bithermal caloric test, earth vertical axis rotation (EVAR) and head impulse test (HIT)) and otolith function evaluation (cervical vestibular evoked myogenic potentials). Information regarding the hearing evaluation of the patients were also retrieved including impedance tympanometry, distortion product otoacoustic emissions (DPOAEs), air and bone conduction audiometry and auditory brainstem response (ABR).
Results: Vestibular responses were impaired for canal responses (only at high and middle head velocities) and vestibulospinal otolithic responses. Oculomotor abnormalities were frequent, mostly hypermetric saccades and gaze instability. Inhibition of the vestibulo ocular reflex by fixation was normal. Abnormal neural conduction in the central auditory pathways was frequently observed.
Conclusions: We show that Friedreich ataxia, even at onset, frequently associate saccadic intrusions, abnormal ABRs and decreased vestibulo ocular and vestibulospinal responses progressing over time. These sensory impairments combined with ataxia further impair patient’s autonomy. These vestibular, auditory and visual impairments could be used as markers of the severity and progression of the disease. Adding vestibular and auditory testing to ataxic patient’s evaluation may help physicians to distinguish Friedreich ataxia from other progressive ataxia syndromes and improve patient’s management.