Efferent Influence on Vestibular Function Following Unilateral Labyrinthectomy

Abstract

Central compensation following unilateral labyrinthectomy has been studied and discussed in an earlier paper (Fluur, 1960). By depressing the activity in the intact labyrinth by means of cold water irrigation, it was possible to demonstrate a gradual return of the normal function via compensatory activation of the vestibular nuclei on the labyrinthectomized side. Bárány (1906, 1907) conducted rotatory tests on patients bereft of one labyrinth due to acute labyrinthitis. He found far greater sensitivity to ampullopetal than to ampullofugal endolymph currents, and sought to explain the phenomenon on the basis of Ewald's (1892) view that the horizontal semicircular ducts had a uni-directional sensitivity which could come into play only after loss of one labyrinth. Cawthorne, Fitzgerald & Hallpike (1942) reported caloric tests of patients who had undergone unilateral labyrinthectomy; they too, demonstrated increased sensitivity to ampullopetal endolymph currents. They termed this phenomenon “directional preponderance” and attributed it to conversion of the normal bi-directional sensitivity “into an abnormal uni-directional type”. Since different authors have placed different interpretations on their results, it has been considered worth while to investigate the possible effects of unilateral labyrinthectomy on the function of the intact labyrinth.