Behavior of the vestibular nerve following labyrinthectomy.

Transtympanic labyrinthectomy was performed on 24 cats, and after survival times of one month to three years, the temporal bones were prepared for light microscopic study. The operated ears showed mean neuronal losses of 12% in six months, 24% in 1 year, 35% in 2 years, and 53% in 3 years. These was no evidence of regeneration of vestibular nerve fibers nor of formation of traumatic neuromata. The temporal bones of two human subjects who had undergone transtympanic labyrinthectomy are also presented; one shows atrophy of the vestibular nerves while the other exhibits proliferation of nerve fibers not resembling a neuroma. It is concluded that the afferent vestibular nerves undergo slow but progressive atrophy following labyrinthectomy and that they have no potential for the creation of amputation neuromata. The evidence suggests that excision of the vestibular nerves may have no therapeutic advantage over labyrinthectomy in the treatment of intractable vertigo.