The effect of cochlear implants on vestibular-evoked myogenic potential responses in adults

Abstract

Background Cochlear implants (CIs) as a golden solution for improving hearing for patients with profound hearing loss may although causes damage for peripheral vestibular system during insertion of electrode interpretatively leading to vestibular dysfunction. This can be assessed by several methods. One of the important methods is cervical vestibular evoked myogenic potential (cVEMP) which can assess the function of saccule. Aim of the work Study the effect of insertion of electrodes of CIs on the saccular function, by using cVEMP test which was performed before and after the operation. Also, cVEMP was measured in the CI-on and CI-off modes to determine if electrical stimulation of electrodes of CIs affects the saccular function or not. Materials and method Thirty adult CI candidates were recruited from the audiology unit of Hearing and Speech Institute. cVEMP was recorded preoperatively for each candidate and two months post operative. cVEMP testing was performed in the CI-on and CI-off modes. Results cVEMP response was recorded postoperatively for 19 out of 30 (63%) implanted ears. The amplitude of wave P and wave N in implanted ears with CI-off mode was decreased compared to preoperative results and this decrease is statistically significant. Also, amplitude of wave P and wave N in implanted ears with CI-on mode were increased compared to preoperative results and this increase is statistically significant. The interaural amplitude difference (IAD) ratio in postoperative CI-on mode was decreased compared to preoperative results and this decrease is not statistically significant. Conclusion cVEMP should be included in cochlear implant selection protocol with caloric testing as it is more sensitive for discovering vestibular disorders. Also, postoperative cVEMP testing in the CI-on and CI-off modes will offer accurate evaluation of saccule function after CI surgery.