Change in vestibular function and vertigo after cochlear implantation

Abstract

Background: The evaluation of vestibular function and symptomatic vertigo before and after cochlear implantation (CI) is important. The objective of this study was to test the vestibular function after CI and to evaluate the correlation with symptomatic vertigo and postoperative vestibular impairment as risk factors. Material and methods: Twenty-five adult patients who had undergone CI at our hospital between September 2005 and September 2010 were studied. All the patients were subjected to caloric tests and the measurement of vestibular-evoked myogenic potentials (VEMP) pre-and postoperatively. Postoperative vertigo and nystagmus were assessed and their correlations with the results of the caloric tests and the VEMP measurements were examined. Results: Ten of the 25 cases (40.0%) exhibited canal paresis on the preoperative caloric tests and 11 of the 25 cases (44.0%) exhibited low VEMP responses. Five of the 18 cases (27.8%) showed reduced caloric responses, and 4 of the 14 cases (28.6%) showed reduced VEMP responses after CI. Thirteen of the 25 cases (52.0%) complained of vertigo after CI, and 17 of the 25 cases (68.0%) showed spontaneous nystagmus postoperatively. Preoperative vertigo and the duration of hearing loss were significantly different between the patients with and those without postoperative vertigo. The patient age at the time of the operation, gender, cause of hearing loss, and type of implant device were not correlated with the change in vestibular functions, vertigo, or nystagmus after CI. Conclusion: Postoperative vertigo and nystagmus were not correlated with the preand postoperative caloric responses and the VEMP. Acute vertigo attacks may have been induced by acute inflammation of the labyrinth as a result of the cochleostomy and electrode insertion. Delayed vertigo attacks may have resulted from chronic changes within the inner ear, including endolymphatic hydrops.