Risk Factors for Facial Nerve and Other Nonauditory Side Effects Following Cochlear Implantation

Objective: The purpose of this study was to characterize a cohort of patients with nonauditory side-effects (NASx) following cochlear implant (CI) surgery. Study Design: Retrospective case review. Setting: Tertiary referral center. Patients: One hundred twenty three multichannel CI recipients with intraoperative facial nerve stimulation (FNS). Intervention(s): Intraoperative electrical auditory brainstem responses (eABR) during CI surgery. Main Outcome Measure(s): Nonauditory side effects post-CI activation. Results: Intraoperative FNS was identified in 2.26% of patients (123/5441), of whom, 34% (42/123) experienced VII stimulation on CI activation. Pain was experienced by 22% (27/123) and vestibular dysfunction was experienced by 4% (5/123) of cases. All case who experienced pain and/or vestibular NASx also experienced VII stimulation. The majority of cases were managed by CI remapping or observation and habituation. Significant relationships were found between etiology of hearing loss and presence of FNS upon initial activation (p<0.05). No significance was found between FNS intraoperatively and at initial activation for all assumed mechanisms of hearing loss ( p>0.05) with the exceptions of acquired hearing loss of undetermined etiology and toxic etiology group ( p<0.05). There was no significant impact of implant array design (p>0.05). Conclusions: This study has characterized patients with NASx in a large cohort of CI patients. One third of cases identified with FNS intraoperatively, developed NASx post-CI activation. Risk factors for NASx postactivation include high-risk etiologies and intraoperative objective measures (i.e., eABR). This may assist surgeons and audiologists to identify at-risk patients who may need modifications in CI program planning. Key Words: Cochlear implant—Electrical auditory brainstem responses—Facial nerve stimulation—Nonauditory side-effects.