Abstract
Acoustic neuromas are benign tumors that usually arise within the internal auditory canal from the vestibular nerve. The therapeutic goal of acoustic neuroma surgery is total tumor excision with preservation of the facial nerve and hearing function. Currently, a preservation rate of facial nerve function has been achieved of around 90-95%, so we can give the patient satisfactory results. However, the rate of hearing preservation is still not high. By just preserving the cochlear nerve anatomically, the function of the cochlear nerve which is part of the central nervous system cannot be preserved. In order to preserve the hearing function, we thought that highly sensitive, stable and continuous monitoring would be extremely useful, which can visualize the change of hearing function in real-time. Therefore, we developed a hearing preservation operation using a new method of intraoperative continuous cochlear monitoring.
The auditory brainstem response as the conventional way of monitoring hearing function is convenient, but it needs 30 to 60 seconds to achieve average values. To create a quicker and more sensitive monitoring of hearing function, we came up with the idea of placing a special electrode on the dorsal cochlear nuclei. What is most characteristic of our monitoring surgery is to be able to operate while monitoring the status of the hearing function every 6 to 12 seconds without stopping the surgical procedure. We have termed the obtained action potential "DNAP": Dorsal cochlear nucleus action potential. During tumor removal, we observe the amplitude of the DNAP. In the event that a sudden decline is noted, we make it a rule to stop all surgical procedures and wait by 15th of minutes. We emphasize that maximizing the recuperation period in the extended recuperation treatment strategy after reversible injury may improve the outcome after acoustic neuroma surgery. Our hearing preservation rate after acoustic neuroma has improved to more than 70%.
