Vestibular Function After Bilateral Simultaneous Cochlear Implantation

Objectives: Thanks to the advantages of hearing-in-noise and spatial orientation, currently bilateral cochlear implantation (CI) became popular for patients with profound hearing loss. The aim of this study was to investigate vestibular function in bilateral simultaneous CI recipients. Study Design: Retrospective analysis. Setting: University hospital. Patients: Sixteen patients with profound hearing loss were included. Interventions: Bilateral simultaneous CI with flexible electrode using round window approach. Main Outcome Measures: Vestibular function was evaluated using both objective and subjective measures in the subjects preoperatively and 4 months postoperatively. Differences were analyzed preoperatively and postoperatively. Results: Preoperative vestibular tests revealed that 8 subjects (50%) had abnormal caloric test results, 11 ears (34.4%) had abnormal ocular vestibular-evoked myogenic potential results, 6 ears (18.8%) had abnormal cervical vestibular-evoked myogenic potential results, 7 ears (21.9%) in the anterior semicircular canal, and 6 ears (18.8%) in the posterior semicircular canal had gain loss. However, surgery significantly decreased the sums of the maximal slow-phase velocities evidenced by caloric test (p < 0.05). Cervical vestibular-evoked myogenic potential abnormal rate significantly increased to 53.1% after surgery (p < 0.05). The postoperative changes regarding ocular vestibular-evoked myogenic potential, video head impulse test (vHIT), and Dizziness Handicap Inventory (DHI) were not significant among all the patients. Patients diagnosed as large vestibular aqueduct syndrome showed significantly higher DHI scores than others (p < 0.05). Spearman's correlation analysis revealed that DHI moderately correlated with the dysfunction of semicircular canals evidenced by vHIT (r = 0.702; p < 0.001), weakly correlated with caloric (r = 0.352; p = 0.048). However, no correlation was found between DHI and VEMPs. The monosyllabic and disyllabic word recognition score significantly improved from 0 to 60.4 +/- 14.3% (p < 0.05) and from 0 to 63.3 +/- 14.5% (p < 0.05) respectively. There was no correlation between the improvement of word recognition score and the change of vestibular tests. Conclusion: The study showed preservation of utricle function, vestibular function at high frequency after bilateral simultaneous CI. However, operation significantly affected vestibular function at low frequency and saccule function. Patients with large vestibular aqueduct syndrome showed dramatically higher DHI scores than others. DHI moderately correlated with vHIT and weakly correlated with caloric.