Intraoperative auditory monitoring in acoustic neuroma surgery

Intraoperative auditory monitoring is a useful adjunct that is currently evolving. Near-field monitoring techniques such as electrocochleography and direct eighth nerve compound action potential are being used more frequently. The use of these two techniques is compared in 26 patients undergoing hearing preservation acoustic neuroma resection. Overall, 9 (35%) of the 26 patients had their hearing preserved. Three (23%) of the 13 with electrocochleography monitoring and 6 (46%) of the 13 with direct compound action potential monitoring had hearing preserved after surgery. Although there was a suggestion of improved results with direct compound action potential monitoring, the results were not statistically different. It was noted that lack of electrical response at the completion of the procedure (regardless of monitoring technique) was correlated with poor postoperative hearing, whereas the presence of a waveform at termination in no way predicted satisfactory postoperative hearing. The two techniques and their advantages and disadvantages are discussed.