Compensation after sudden loss of unilateral vestibular function and optokinetic after-nystagmus.

UNLABELLED: After unilateral labyrinthectomy or vestibular neurectomy, optokinetic after-nystagmus (OKAN) to the ipsilateral side was abolished, then gradually recovered. We studied whether the compensation could be evaluated by observing OKAN.

METHODS: Unilateral labyrinthectomy or vestibular neurectomy was performed under general anesthesia in cases of severe inner ear origin vertigo. Eye movements were recorded by electronystagmography (ENG), and the duration of OKAN was measured.

RESULTS: The duration of OKAN to the ipsilateral side was shorter than that to the contralateral side (85%), the ipsilateral side was longer in 15% after labyrinthectomy. After vestibular neurectomy, the duration of OKAN to the ipsilateral side was shorter in 90%, and in 10% it became symmetrical.

CONCLUSION: The stage of compensation after unilateral labyrinthectomy or vestibular neurectomy can be seen by measuring the duration of OKAN.