Surgical technique for implantation of the totally ossified cochlea

Among the technical challenges of cochlear implant surgery is electrode insertion into the fully ossified cochlea. Earlier drill-out techniques have two significant drawbacks: 1. up to one half fail when the electrode pulls away from the cochlea; and 2. extended radical mastoidectomy, abdominal fat graft for obliteration, and closure of the external auditory meatus are required. A simplified technique is described that allows positive fixation of the cochlear implant electrode and in selected cases avoids a radical cavity with obliteration.

Technical description with case reports and hearing outcomes.

Ten cadaver temporal bones were dissected to determine middle ear landmarks that overlie the basal turn of the cochlea from the transcanal approach and to establish the feasibility of the intact canal wall procedure. Surgery was performed on four patients who had preoperative imaging evidence of full ossification, two with the canal wall down, and two with canal wall up. Standard measures of speech recognition were used to evaluate hearing.

Critical surgical landmarks are the round window, carotid artery, cochleariform process, and oval window. The procedure was successfully performed on four patients and open-set speech recognition is present in each.

This canal wall up procedure allows long electrode insertion without radical cavity/obliteration in patients with fully ossified cochleas and prevents distraction of the electrode from the cochlea. While open-set word recognition was achieved by all subjects, results are poorer than expected for patients with limited or no ossification.