Facial nerve stimulation outcomes after cochlear implantation with cochlear-facial dehiscence

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ObjectivesTo examine the occurrence of facial nerve stimulation (FNS) and outcomes in patients with cochlear-facial dehiscence (CFD) who underwent cochlear implantation (CI). MethodsThe medical charts and imaging of three patients with bilateral sensorineural hearing loss (SNHL) who presented for CI evaluation were reviewed. ResultsPatient 1 (P1) had a history of Meniere's disease. Patient 2 (P2) had a history of medulloblastoma treated with surgery and chemoradiation. Patient 3 (P3) had a history of progressive SNHL. Audiometry showed moderate-to-severe SNHL in P1, severe-to-profound SNHL in P2, and profound SNHL in P3. All had poor speech discrimination ability. Temporal bone computed tomography (CT) coronal cuts were suspicious for bilateral dehiscence between the superior basal turn of the cochlea and labyrinthine segment of the facial nerve in P2 and P3, with maximum dehiscence lengths of 2.0 mm on the left in P2, and 1.8 mm on the right in P3. A thin bony partition was visualized bilaterally in P1. The left ear of P1, left ear of P2, and right ear of P3 were implanted. Facial nerve stimulation occurred immediately upon activation in P1 and P2, which resolved by decreasing the dynamic range of the offending electrodes. No FNS was observed in P3. ConclusionCochlear-facial dehiscence can predispose patients to post-implant FNS. Prior temporal bone irradiation may carry a higher risk of FNS. We recommend scrutiny for CFD in CTs of CI candidates and appropriate risk counseling for FNS if CFD is discovered and more frequent monitoring for FNS by audiology.