Influence of cochlear implantation on sacculus function.

OBJECTIVES: To examine the influence of cochlear implantation (CI) on the sacculus function and to analyze a possible correlation with resulting vertigo symptoms. METHODS: In a prospective study including 25 patients undergoing CI, preoperative and postoperative assessment of vestibular evoked myogenic potentials (VEMP), caloric horizontal semicircular canal (hSCC) response, and subjective vertigo symptoms were assessed. The patients with postoperative vertigo were compared to the patients without postoperative vertigo with regard to the findings of VEMP responses and caloric testing. RESULTS: Nine patients reported postoperative vertigo. Before surgery, eight of 23 patients (35%) had regular VEMP responses. Two months after CI, four patients had a new loss of sacculus function on VEMP testing. The CI represents a significant risk factor for sacculus impairment. In seven of 12 patients with preoperatively preserved caloric response, this decreased after the operation. The impaired vestibular function did not correlate with vertigo symptoms. When comparing the patient group with vertigo and the group without vertigo after CI, there is a significant difference in the patients' age. CONCLUSIONS: Although CI can cause damage to sacculus and hSCC function, this is probably not the only cause for postoperative vertigo. Advanced age is a significant risk factor for vertigo after CI.