Cochlear implant and vestibular function.
OBJECTIVES: To document incidences of vestibular dysfunction after cochlear implantation and investigate why it occurs. This work was also motivated by a desire to provide the basis for better preoperative counseling and postoperative vestibular therapy to cochlear implant patients. SETTING: Melbourne Cochlear Implant Clinic at a tertiary referral hospital. STUDY DESIGN: Prospective observational study. PATIENTS: One hundred forty-six adult implant recipients, mean age, 60 years (range, 20-90 yr). MAIN OUTCOME MEASURES: Postoperative vestibular disturbance was defined as symptoms lasting for 1 week or longer after surgery. The differences in preoperative and postoperative vestibular function were measured from subjective assessments (Dizziness Handicap Inventory and Activity Balance Confidence questionnaires) and objective assessments (bithermal caloric tests). The position of the postoperative electrode was classified as "loose", "regular", or "tight" fitting. RESULTS: Thirty-two percent of patients reported vestibular disturbance and had poorer Dizziness Handicap Inventory, Activity Balance Confidence, and caloric results in the implanted ear after surgery. Patient age, cause, and preoperative caloric result did not predict postoperative vestibular symptoms. Recipients aged 70 years or older had significantly poorer caloric results on the implanted side after surgery that was not related to the intracochlear electrode position or surgical team. CONCLUSION: One-third of recipients can expect to experience a significant vestibular disturbance after surgery, regardless of age, cause, or preoperative caloric result. "Older" ears seem more prone to permanent injury after cochlear implantation.