SURGICAL TECHNIQUE FOR IMPLANTATION OF THE TOTALLY OSSIFIED COCHLEA

Objectives: 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 radic al 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 electr ode and in selected cases avoids a radical cavity with obliteration. S tudy Design: Technical description with case reports and hearing outco mes. Methods: Ten cadaver temporal bones were dissected to determine m iddle ear landmarks that overlie the basal turn of the cochlea from th e transcanal approach and to establish the feasibility of the intact c anal wall procedure. Surgery was performed on four patients who had pr eoperative imaging evidence of full ossification, two with the canal m all down, and two with canal wall up. Standard measures of speech reco gnition were used to evaluate hearing. Results: Critical surgical land marks 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. Conclusions: This canal wall up procedure allows long electrode insertion without radic al cavity/obliteration in patients with fully ossified cochleas and pr events distraction of the electrode from the cochlea. While open-set w ord recognition was achieved by all subjects, results are poorer than expected for patients with limited or no ossification.