Special Surgical Considerations

In cases of cochlear dysplasia, a cerebrospinal fluid (CSF) gusher may be encountered. The senior author prefers to enter the cochlea through a small fenestra and tightly pack the electrode at the cochleostomy with fascia. The flow of CSF has been successfully controlled in this way. In patients with severe malformations of the labyrinth, the facial nerve may follow an aberrant course. In these cases, the most direct access to a common cavity deformity may be by a transmastoid labyrinthotomy approach. The otic capsule is opened posterosuperior to the second genu of the facial nerve, and the common cavity is entered directly. Four patients have been treated in this way with no vestibular side effects.33

In cases of cochlear ossification, our preference is to drill open the basal turn and create a tunnel approximately 6 mm in length and partially insert a Nucleus electrode. This approach permits implantation of 10 to 12 active electrodes, yielding very satisfactory results. Gantz et al.34 described an extensive drill-out procedure to gain access to the upper basal turn. The benefits of this extended procedure are under investigation. Steenerson et al.35 described the insertion of the active electrode into the scala vestibuli in cases of cochlear ossification. This procedure has merit. However, the scala vestibuli is frequently ossified when the scala tympani is completely obliterated.

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