Impaired reaching adaptation links to vestibular symptoms

Abstract About 30% of adults suffer from some mild to severe vestibular dysfunction. Vestibular disorders can be expressed as acute vestibular syndrome (AVS), episodic vestibular syndrome. Only half of the sufferers can compensate for their dysfunction after three months after the onset, while the other half of them become chronic, the mechanisms behind this compensation remain unclear. Several behavioural studies have explored the role of the vestibulo-ocular reflex and saccades in the process, linking to the interaction between the superior colliculus and the cerebellum. Yet, despite cerebellar involvement in vestibular function and oculomotor adaptation, thus far, no studies have focused on the specific role of the cerebellum in the compensation process in vestibular dysfunction. In this study, we test the hypothesis that undiagnosed cerebellar dysfunction might hinder chronic vestibulopathy sufferers from compensating and recovering. We recruited 19 patients who had suffered from an acute peripheral vestibular syndrome (10 clinically recovered and 9 with chronic symptoms) and ten individuals with no history of vestibular alterations (controls). We assessed their implicit motor learning capacity with a visuomotor rotation task and measured by the angular aiming error, which showed an impaired implicit motor adaptation in chronic patients (7.04 ± 1.6º) compared to recovered (11.06 ± 1.94º, p = 0.007) and control groups (10.89 ± 7.96º, p = 0.03). These findings indicate the involvement of the cerebellum in vestibular compensation and suggest that implicit motor adaptation of reaching movements could be potentially used as an early prognostic tool in unilateral peripheral vestibular dysfunction (UPVD) patients.