VESTIBULAR COMPENSATION AFTER LABYRINTHECTOMY AND VESTIBULAR NEURECTOMY IN CATS

Labyrinthectomy and vestibular neurectomy are two ablative procedures used for definitive control of disabling vertigo. It is not known if vestibular compensation after labyrinthectomy and vestibular neurectomy differs. We have addressed this question by examining the pattern of recovery of the vestibular ocular reflex in cats after either labyrinthectomy or vestibular neurectomy. Temporal bone histologic examination confirmed the surgical lesion. Our results demonstrate a reduction of the long time constant of the vestibular ocular reflex in both groups of animals. Although gain of the vestibular ocular reflex recovered substantially, it never returned to control levels in either group. In general, animals that had undergone vestibular neurectomy demonstrated greater vestibular ocular reflex asymmetries than did labyrinthectomized animals. The recovery pattern of the vestibular ocular reflex indicates vestibular compensation is more rapid after labyrinthectomy than after vestibular neurectomy. We believe this result is related to survival of the vestibular nerve after labyrinthectomy, but not after vestibular neurectomy, suggesting that the vestibular nerve can contribute to the adaptive response after labyrinthectomy.