Caloric stimulation of the vestibular organ after cochlear implant surgery

Background: Alterations of the vestibular organ after intracochlear insertion of the electrode array in cochlear implant (CI) surgery are estimated in the literature to be more than 30% [1 - 5]. By performing a most atraumatic electrode insertion following the soft surgery technique as described by Lehnhardt [6], the risk of postoperative vestibular dysfunction should be minimised. Methods: In the present study we compared pre- and postoperative results of the caloric stimulation test in cochlear implant patients and analysed the influence of untimely opening of the perilymphatic space under cochleostomy. In addition we used a nonvalidated questionnaire, asking for continuous postoperative vertigo after cochlear implant surgery. Results: From patients with preoperative normal or hyperfunction on the implanted ear (n = 32) approximately 16% showed a hypofunction or nonfunction on the implanted side postoperatively, independent of the technique of the cochleostomy. Only 12% (n = 98) of the patients who were without vestibular problems preoperatively described postoperative vertigo longer than two days in the questionnaires. Conclusions: Although we found no significant difference regarding the influence of the technique of the cochleostomy on the preservation of vestibular function, we conclude that the concept of an atraumatic electrode insertion reduces the risk of vestibular dysfunction after CI-surgery.