Scala vestibuli cochlear implant supported by 3D modeling of the inner ear

Abstract

Patients with scala tympani (ST) ossification present a distinct surgical challenge. Three-dimensional (3D) segmentation of the inner ear offers accurate identification of ossification and surgical planning of the cochleostomy to access the scala vestibuli. The scala vestibuli placement of cochlear implantation electrode is an alternate solution in these patients and is well supported by the literature. The present report describes a case of cochlear implantation in the scala vestibuli assisted by 3D segmentation of the cochlea for a patient with ossification in the ST and reviews the relevant literature. Clinical presentation of a 45-year-old Austrian female who was referred with a history of sudden sensorineural hearing loss 2 years ago in the right ear, confirmed by pure tone audiometry (PTA) and acoustically evoked auditory brainstem response (ABR). 3D segmentation of the inner ear identified the extent of ossification in the ST and assisted in the surgical planning of cochleostomy drilling anterior-superior to the round window to access the scala vestibuli for the electrode placement. Postoperative computed tomography (CT) to confirm the electrode placement in the scala vestibuli and PTA was performed to assess the hearing threshold following the cochlear implantation. Postoperative CT confirmed the full insertion of a flexible electrode. The hearing threshold measured by PTA was ≤ 40 dB across all frequencies tested. Review of the literature identified a total of 13 published reports on cochlear implantation electrode placement in scala vestibuli in cases with ossification in the ST.