Cochlear Implantation Rarely Alters Horizontal Vestibulo-ocular Reflex in Motorized Head Impulse Test

Objective: Determine the change in vestibular function in patients receiving a unilateral cochlear implant, and to compare these results with other signs and symptoms. Study Design: Prospective cohort study. Setting: Academic tertiary referral center. Patients: Forty-four adults (mean age, 55 yr; range, 30-76 yr) receiving their first cochlear implant. Intervention: Cochlear implantation. Main Outcome Measures: Horizontal high-frequency vestibulo-ocular reflex (VOR) was measured using the motorized head impulse rotator preoperatively and twice (on average two and 19 months) postoperatively. VOR gain and asymmetry were calculated (mean +/- standard deviation). Symptoms were assessed with a structured questionnaire. Results: Gain on the operated side was 0.77 +/- 0.26 preoperatively, 0.75 +/- 0.30 in the early and 0.73 +/- 0.33 in the late postoperative control, and did not change significantly. Mean asymmetry remained within 9% to 10% in all test occasions. Dizziness symptom score or dizziness-related quality of life score did not change significantly. General quality-of-life score improved significantly from that of preoperative 3.5 +/- 1.2 to that of 2.6 +/- 1.1 postoperatively (p = 0.01). Subjective hearing scores improved significantly from 4.9 +/- 0.3 to 2.4 +/- 1.0, respectively (p = 0.0000). Gain was decreased significantly in 4 patients (10%) in the early and in 2 patients (7%) in the late postoperative control. Conclusion: Late high-frequency loss of vestibular function or vestibular symptoms is rare but possible after cochlear implantation surgery. This should be taken into account in patient counseling especially when considering bilateral cochlear implant surgery.