Vestibular and taste disorders after bilateral cochlear implantation.

The objective of this study was to investigate the occurrence of vestibular receptor deficiency and taste disorders after bilateral cochlear implantation in postlingually deafened patients and to find out whether the risk for these complications is higher for the second implantation. In a retrospective cohort study, we examined 20 patients (11-58 years, mean age 41.5 years), implanted sequentially between 2000 and 2007 (mean period between cochlear implantation 32.9 ± 25 months). Pre- and postoperative vestibular testing was performed by subjective rating [Dizziness Handicap Inventory (DHI)], caloric irrigation [vestibuloocular reflex (VOR)] and by vestibular-evoked myogenic potential (VEMP) recordings for saccular function. The sense of taste was evaluated pre- and postoperatively by a questionnaire and testing (sour/sweet/bitter/salty bilaterally on the tongue). DHI evaluation showed a moderate not significant mean increase by 2.7 ± 7.7 SD points after the first and a significant increase by 9.4 ± 16.6 SD points after the second implantation. Ipsilateral VEMP responses disappeared in three ears (27.3%) after the first and in two ears (18.2%) after the second operation. VOR disappeared only once (5.9%) after the first implantation. One (5%) patient complained of a persisting disturbance of taste in the questionnaire after unilateral and 3 (15%) after bilateral implantation. Specific testing showed in one case (5%) a unilateral taste disorder after ipsilateral cochlear implantation. Our data show that there is a higher risk for subjective vertigo after the second implantation. The occurrence of unilateral and/or bilateral vestibular dysfunction and the potential risk of taste disorder should be included in the risk counseling before bilateral cochlear implantation to increase patients' and medicolegal safety in the decision-making process.