Gentamicin-induced bilateral vestibulopathy in rabbits: vestibular dysfunction and histopathology.

OBJECTIVES/HYPOTHESIS: Bilateral vestibulopathy (BV) is a mostly persistent and disabling disorder causing dizziness, oscillopsia, and imbalance during locomotion. The animal model is a prerequisite for experimental investigation on prevention and treatment of this disorder. The aim of this study was to determine the vestibular dysfunction and histopathology in rabbits with gentamicin-induced BV.

STUDY DESIGN: Prospective animal study in rabbits.

METHODS: We performed intratympanic gentamicin (ITGM) injections in 12 Lionhead rabbits. The injection was applied to each ear with a 3-day interval. The control group received injections of 0.9% normal saline. The animals were subjected to sinusoidal harmonic accelerations and open field tests for evaluation of the vestibular function before and after the procedures. We also determined histologic changes in the vestibular labyrinth 30 days after the first injection.

RESULTS: One day after unilateral ITGM injection, the rabbits mostly showed ipsiversive head tilt, contralesional spontaneous nystagmus, ipsiversive circling behavior, and decreased gain of the vestibulo-ocular reflex (VOR) during ipsiversive rotation. The second injection to the contralateral ear improved the head tilt but induced marked reduction in the activities and the VOR gains in both directions. These changes persisted until the histologic study confirmed the loss of the hair and supporting cells, diminished nerve fibers, and thinning of the sensory epithelium of the cristae ampullaris and otolith organs in the ITGM group 1 month later.

CONCLUSIONS: ITGM injection securely induced BV in rabbits without side effects such as nephrotoxicity. This rabbit model may be utilized for experiments on the prevention and treatment of BV.