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 success ful monitoring of cochlear compound action potentials; 20 were not mon itored because their surgery predated monitoring; and 4 had unsuccessf ul monitoring. A significant difference was found in hearing preservat ion rates between the group in whom compound action potential monitori ng was performed and those in whom monitoring was either unavailable o r failed (p = 0.02). Overall, 38% (30 of 80) had preserved hearing. Th ere were 51 patients in whom the click threshold for the cochlear comp ound action potential was measured during surgery. Twenty-one patients had a threshold shift of 20 dB or less, 15 (71%) of these retained se rviceable 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 service able hearing after surgery. The click threshold shift was predictive o f a Significant postoperative hearing change (p < 0.001].