Influence of cochlear implantation on peripheral vestibular receptor function

Abstract

Objective: The objectives of this study were 1) to assess the influence of a cochlear implantation on peripheral vestibular receptor function in the inner ear in the implant and in the nonimplant side, and 2) to analyze a possible correlation with resulting vertigo symptoms. Study Design: Prospective clinical study. Setting: Cochlear implant center at tertiary referral hospital. Subjects and Methods: A total of 32 patients, aged 15 to 83 years, undergoing cochlear implantation were assessed pre- and postoperatively for caloric horizontal semicircular canal response and vestibular-evoked myogenic potentials of the sacculus, and postoperatively for subjective vertigo symptoms. Patients with vertigo were compared with patients without symptoms with regard to the findings of the vestibular function tests. Results: Cochlear implantation represents a significant risk factor for horizontal semicircular canal impairment ( P < 0.001) and sacculus impairment ( P = 0.047) in the implanted ear. In eight of 16 patients with preoperatively preserved caloric response, this response was decreased postoperatively. Before surgery, 14 of 30 patients had regular vestibular-evoked myogenic responses. Two months after implantation, six patients had a new loss and another six showed depression of sacculus function on vestibular-evoked myogenic potentials testing. The impaired vestibular function did not correlate with vertigo symptoms. Function on the contralateral side remains unaffected ( P > 0.05). Conclusion: Cochlear implantation is a relevant risk factor for damage of peripheral vestibular receptor function. Therefore, preservation not only of residual hearing function but also of vestibular function should be aimed for, by using minimally invasive surgical techniques.