Analysis of postoperative vertigo or dizziness in cochlear implant patients

Cochlear implants (CIs) are associated with a potential risk for vestibular system insult or stimulation with resultant dysfunction. Twenty-six patients underwent equilibrium tests before undergoing CI surgery at our institute. As part of the equilibrium tests, a caloric test, static posturography, observation of nystagmus using an infrared CCD camera, and measurement of the vestibular-evoked myogenic potential (VEMP) were performed. Half of the patients (13 out of 26 patients) complained of vertigo or dizziness after the operation. In most patients (12 out of 13 patients), these symptoms occurred immediately after the operation and disappeared within one week. Patients who did not complain of vertigo or dizziness after the CI surgery had a statistically significant lower response for the caloric testing than the patients who experienced these symptoms. No significant differences in the static posturography, nystagmus and VEMP test results were seen between the group of patients who did not complain of vertigo or dizziness after the CI surgery and the group of patients who experienced these symptoms. This result suggests that the patients with normal peripheral vestibular functions preoperatively had a greater tendency to complain of vertigo or dizziness after the operation. The cause of postoperative vertigo or dizziness was judged to be due to the peripheral vestibular function before surgery. It is important for CI candidates to undergo equilibrium tests preoperatively as means of predicting postoperative vertigo or dizziness.