Successful Cochlear Implantation of a Split Electrode Array in a Patient With Far-advanced Otosclerosis Assisted by...

Incomplete electrode insertion is frequent when implanting ossified cochleae with conventional linear electrodes. If split electrode arrays (SEA) are used, this complication occurs less frequently resulting in improved audiological performance (AP). Additional implementation of electromagnetic navigation systems (EMNS) may add additional safety to this procedure and may further improve AP. However, previously performed SEA cochlea implantations rarely implemented EMNS. The few cases reported a laborious approach with customized, three-dimensional-printed microstereotactic headframes, which limited clinical feasibility. Moreover, no postoperative AP was reported. In this case report a more feasible approach, using a commercially available EMNS, is described and postoperative AP is reported.

A 70-year-old man with far-advanced otosclerosis was referred because of unsatisfactory speech intelligibility (monosyllabic word score of 0% at 75 dB sound pressure level) after cochlear implantation of a conventional linear electrode. Preoperative computed tomography revealed subtotal cochlear ossification and incomplete electrode insertion.

Four titanium screws were inserted into the petrous bone for computed tomography-based registration using an EMNS. The previous mastoidectomy was expanded, the misplaced conventional linear electrode extracted and a manual, free-handed superior cochleostomy at the level of the tendon of the tensor tympani muscle was performed. The location and course of the drill-out procedure for the SEA was planned and verified with EMNS.

Full electrode insertion for both electrode arrays of the SEA was achieved without any nerve dysfunction. Monosyllabic word score, determined 207 days after surgery, improved to 50 and 60% at 65 and 75 dB sound pressure level respectively.

The implementation of EMNS in SEA cochlear implantation added additional safety to the procedure, which resulted in full electrode insertion and superior AP. Yet, outcome in cochlear implantation may vary. Larger case series to confirm this observation are required. The approach proposed for EMNS-guided SEA in this case report, using commercially available EMNS, may lead to a more frequent implementation in clinical routine due to its good clinical feasibility. Thus, larger case series may be generated.