HEARING PRESERVATION IN ACOUSTIC NEUROMA SURGERY - VALUE OF MONITORING COCHLEAR NERVE ACTION-POTENTIALS

This study reviews the hearing results in 80 consecutive patients who underwent complete removal of histologically proven acoustic neuromas by use of the suboccipital approach. Of these, 56 patients had successful monitoring of cochlear compound action potentials; 20 were not monitored because their surgery predated monitoring; and 4 had unsuccessful monitoring. A significant difference was found in hearing preservation rates between the group in whom compound action potential monitoring was performed and those in whom monitoring was either unavailable or failed (p = 0.02). Overall, 38% (30 of 80) had preserved hearing. There were 51 patients in whom the click threshold for the cochlear compound action potential was measured during surgery. Twenty-one patients had a threshold shift of 20 dB or less, 15 (71%) of these retained serviceable hearing (speech reception threshold less than or equal to 50 dB; speech discrimination score greater than or equal to 60%). Of 12 patients in whom the threshold shift was 30 to 60 dB, none had serviceable hearing after surgery. The click threshold shift was predictive of a Significant postoperative hearing change (p < 0.001].