Basal Turn Cochleostomy via the Middle Fossa Route for Cochlear Implant Insertion

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Abstract

Objective: The current article describes the surgical technique and the very preliminary results of insertion of a cochlear implant, via the middle fossa (MF), in patients with middle ear disease.

Study Design: The study design was a case report and a description of surgical technique.

Setting: The study was conducted at an ENT Department, University of Verona, Verona, Italy.

Patients: Two subjects with profound bilateral hearing loss, the first one presenting a bilateral radical mastoidectomy cavity and the second one with fibroadhesive otitis media, were operated on via the current technique.

Intervention: After adequate exposure of the MF floor, a triangular bony area between the greater superficial petrous nerve and the projection of the labyrinthine portion of the facial nerve was drilled out. The basal cochlear turn facing the middle cranial fossa floor was easily encountered, a small cochleostomy measuring 1 1/2 mm in diameter was performed on the most superficial part of the basal turn, and the electrode carrier was inserted into the fenestrated cochlea. The receiver-stimulator was positioned on a bone well drilled previously in the temporal squama.

Main Outcome Measures: The activity of the inserted electrodes was tested by means of telemetry and intraoperative recording of the electrically evoked auditory responses. Speech perception tests, performed 15 and 30 days after cochlear implant activation, showed a remarkable improvement in the outcomes versus the preoperative values that are provided for comparison.

Conclusions: This new surgical approach to cochlear implant insertion via the MF route allows stimulation of part of the basal and the middle and apical areas of the cochlea, where greater survival rates of spiral ganglion cells are observed. Cochlear implant insertion via the MF approach represents a promising technique for auditory rehabilitation of subjects with a bilateral radical mastoidectomy cavity, patients suffering from middle ear malformations or chronic middle ear disease due to eustachian tube dysfunction, or subjects with doubtful responses to promontory stimulation.

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