Vestibular impact of Friedreich ataxia in early onset patients

Abstract

Background: Friedreich ataxia (FRDA) is the most frequent form of inherited ataxias. Vestibular and auditory assessments are 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. Abnormal neural conduction in the central auditory pathways was frequently observed. Oculomotor abnormalities were frequent, mostly hypermetric saccades and gaze instability. Inhibition of the vestibulo-ocular reflex by fixation was normal.

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 Friedreich patient's evaluation may help physicians improve patient's management.

Keywords: Auditory neuropathy; Friedreich Ataxia; Hearing; Vestibular function.

Fig. 1

Proportion of subjects showing normal and abnormal oculomotor and vestibular tests

Fig. 2

Hearing evaluation. Graphic representation of the prevalence of the various observations. Impedancemetry was performed on 41 subjects (82 ears); Hearing evaluation was performed on 40 subjects (80 ears); DPOAEs were evaluated on ears with normal type A tympanometry (69 ears); ABRs were performed on 39 subjects (78 ears)

Fig. 3

Hearing threshold of subjects with normal ABRs in black, and abnormal ABRs in grey. Auditory thresholds are slightly higher in low and high frequencies in the group of patients with abnormal ABR. (*) indicates frequencies with statistically significant difference (U Mann-Whitney test, p < 0,05)

Fig. 4

Correlation between disease duration and EVAR time constant. The longer the disease duration, the shorter the EVAR time constant (Pearson’s correlation, r = − 0.3419, p = 0.04)