Objectives: The National Cochlear Implant Programme at Beaumont Hospital has been providing high quality care for adults with severe to profound hearing loss since 1995. During cochlear implantation a thin flexible electrode array is placed inside the cochlea in the inner ear. This facilitates restoration of hearing and speech following rehabilitation. There may be some effects on the vestibular apparatus during surgery, which has been reported in the literature (Chen 2016). Vestibular dysfunction, including dizziness, decreased balance and impaired walking, after cochlear implantation may occur due to the proximity to the surgical site, but this has not been comprehensively investigated. The aim of the study was to evaluate the prevalence and severity of dizziness, balance and walking problems in cochlear implant users.
Methods: The study design was an observational, cross-sectional, clinical study of a cohort of 16 cochlear implant users. Subjective dizziness was assessed using the Vestibular Rehabilitation Benefit Questionnaire (VRBQ). The presence of Benign Paroxysmal Positional Vertigo (BBPV) was assessed using the Dix-Hallpike test. Gait was measured using the Functional Gait Assessment and walking speed with the 10 metre walk test. Standing balance was assessed using computerised posturography, using the Equitest Balance Manager, with subjective balance confidence during daily tasks evaluated using the Activities Specific Balance Questionnaire (ABC). Dynamic Visual Acuity was measured using the DVA.
Results: Sixteen participants (females=9), with a mean age of 58.4 (SD16.7) years were assessed. Time post implantation varied from one month to ten years. Timed 10 metre walk was 5.8 (SD1.2) seconds with a mean FGA score of 25.3 (SD4.5). The subjective dizziness questionnaire (VRBQ) score was a mean of 6.4 (SD18.1)% and the ABC score 83.5 (SD14.2)%. Dix Hallpike was positive in one participant. Fifty percent of participants lost more than 2 LOGmar on DVA. The mean Equitest score was 59.5 (SD14.2), with 59% of participants demonstrating vestibular dysfunction by falling on balance conditions 5 and 6.
Conclusion: The results of the study provide evidence of vestibular specific balance dysfunction in cochlear implant users. The Equitest provides a high level balance assessment and clear evidence of balance impairment were identified. However, walking was relatively good, potentially indicating adaptation to any vestibular deficit, which is expected in most individuals. Reports of dizziness at the time of assessment were low, although most reported experiencing dizziness post operatively. This again suggests vestibular compensation. The number of included patients was small, limiting statistical analysis and generalisability of findings. However, the findings indicate an unmet need for vestibular assessment and access to rehabilitation when required for this patient group. Further longitudinal investigation of balance, walking and dizziness pre- and post- operatively is required and is currently underway.
References: Chen X, Chen X, Zhang F, Qin Z.Influence of cochlear implantation on vestibular function. Acta Otolaryngol. 2016 Jul;136(7):655-9.
Ethical Considerations: The study protocol was approved by the Beaumont Hospital Medical Ethics Committee (June2016).
