Risk of basilar membrane perforation by intracochlear electrodes.

Insertion of intracochlear electrodes may damage the basilar membrane, the stria vascularis and adjacent structures. When electrodes were placed in human temporal bone specimens, perforations were shown to be independent of the type of implant used, the depth of insertion or the use of a lubricating agent. Helical electrode reinforcements and failure to enlarge the round window frame increase the risk of damage. Perforations are invariably localized at a distance of about 7-14 mm from the round window and occur at the site where the curvature of the basal turn is greatest.