Impact of cochlear implantation on canal and otolith function

Objective: To quantify the impact of cochlear implantation (CI) on all five vestibular end-organs and on subjective ratings of post-CI dizziness. Methods: Seventy-two patients undergoing unilateral CI were recruited for the study. All participants completed pre- and post-CI three-dimensional video head-impulse tests (3D vHITs) to assess semicircular-canal (SC) function, air- and bone-conducted (AC and BC) cervical and ocular vestibular-evoked myogenic potentials (cVEMPs and oVEMPs) to assess otolith-function and the dizziness handicap inventory (DHI) to measure self-perceived disability. Results: Nineteen percent of patients reported new or worsened dizziness postsurgery. Post-CI abnormalities (new lesions and significant deteriorations) were seen in the AC cVEMP (48%), AC oVEMP (34%), BC cVEMP (10%), and BC oVEMP (7%); and lateral (L) (17%), posterior (P) (10%), and anterior (A) (13%) SC vHITs. CI surgery was more likely to affect the AC cVEMP compared with the other tests (χ²test, p < 0.05). Fifty percent of patients reported no dizziness pre- and postsurgery. In the implanted ear, normal pre-CI vHIT gain was preserved in lateral semicircular canal (LSC) (69%), anterior semicircular canal (ASC) (74%), and posterior semicircular canal (PSC) (67%), and normal reflex amplitudes were found in AC cVEMP (25%), AC oVEMP (20%), BC cVEMP (59%), and BC oVEMP (74%). Statistically significant decreases were observed in LSC vHIT gain, AC cVEMP amplitude, and AC oVEMP amplitude postsurgery (p < 0.05). There was a significant moderate positive correlation between change in DHI scores and the summed vestibular deficit postsurgery (r(51) = 0.38, p < 0.05). Conclusion: CI can impact tests that assess all five vestibular end-organs and subjective ratings of dizziness. These results support pre and post-surgical vestibular testing and assist preoperative counseling and candidate selection.