Influence of cochlear implantation on the vestibular function.

The aim of the present study was to examine the influence of cochlear implantation on vestibular function. The function of the horizontal semicircular canal, the saccular function, and the incidence of vestibular symptoms were assessed before and after cochlear implantation. Twenty unilaterally cochlear implant patients were evaluated preoperatively, 1 and 6 months postoperatively, with caloric testing with electronystagmography (ENG) recordings and vestibular evoked myogenic potentials (VEMP) testing. A medical history was taken from every subject, noting the presence or absence of vertigo before and after the operation. A possible correlation between the appearance of postoperative vertigo and age, sex, implant side, preoperative caloric results and VEMP status, and postoperatively recorded changes in caloric and VEMP testing was also investigated. A statistically significant difference was found in the percentages of canal paresis (p = 0.01) and the percentages of VEMP waveform absence (p = 0.002) between the repeated measurements in the implanted side, whereas in the non-implanted side no difference was (p > 0.05) found. Four patients complained of postoperative vestibular symptoms. In three of them the symptoms lasted less than 6 months postoperatively, but the fourth patient was still dizzy 6 months after cochlear implantation. No correlation was found between the above-mentioned factors and the occurrence of postoperative vertigo. In conclusion, although changes of the peripheral vestibular function of the implanted side were recorded in our patients, permanent vertigo was rare. Predictive factors for the occurrence of postoperative vestibular symptoms could not be identified.