Advanced Intraoperative Continuous Cochlear Monitoring and Cochlear Nerve Mapping for CP Angle Surgery: Dramatic Improving the Hearing Preservation

How we can preserve cochlear function in all CP angle surgical cases given that there is a status of reversible cochlear nerve injury? Our first answer is to create continuous and sensitive cochlear monitoring. The second is that we should make the injuring period minimum and the recuperating period maximum immediately after the insult. To this end, we have invented a new intraoperative continuous cochlear monitoring electrode and developed its devices. By using this biocompatible electrode we measure the directly auditory evoked action potential from dorsal cochlear nucleus (DNAP). DNAP voltage is approximately 2 to 10ƒÊV, which is 10 to 100 times the amplitude of ABR. This makes it easy to monitor stably and sensitively. It only needs 50 to 100 times averaging, so it is taking only 3 to 7 seconds. This is “real-time” cochlear monitoring. During the surgery, we try to keep the percentage of the DNAP amplitude to initial amplitude so that it does not go below 40% of the initial amplitude. When it goes below 40%, we stop any surgical maneuver and just to wait for recovering of DNAP at least 15 minutes. This recuperation treatment is one of the keys to hearing preservation in acoustic neurinoma surgery. In addition, by using the monopolar stimulation on the 8th cranial nerve, we can identify cochlear nerve. We call this new technique as cochlear nerve mapping. This new technique is also very powerful tool for hearing preservation surgery. We will show you actual video of cochlear nerve mapping in this round table.