Neurophysiology of Vestibular Compensation

Vestibular compensation is the process by which patients achieve functional recovery after vestibular lesions, and can be divided into static compensation and dynamic compensation. The first stage, static static compensation, consists of eliminating static symptoms (i.e., spontaneous nystagmus and skew deviation) by rebalancing the tonic neural activity in the vestibular nuclei. The second stage, dynamic compensation is much more subtle, takes longer, and involves a central recalibration of the response properties of the vestibulo-ocular reflex (VOR) (i.e., timing and gain) in order to restore the compensatory actions of the VOR to pre-impairment levels. This review is to introduce the normal vestibular function in humans to understand the neurophysiology of vestibular compensation after vestibular lesions, and to review the effects of various types of lesions and the clinical findings in various stages of compensation after each type of lesion. Vestibular compensation is most effective for unilateral vestibular dysfunctions in which tonic neural activity of the vestibular nucleus is rebalanced to achieve static compensation. Adaptive changes in tonic neural activity occur in the normal vestibular pathways to achieve dynamic compensation. In other types of vestibular lesions, vestibular compensation is possible, but not as effective.