Intraoperative Auditory System Monitoring.

A new electrophysiological system for intraoperative, continuous, near-real time monitoring of cochlear nerve function through acoustic stimulation in the ear canal and recording of the evoked dorsal cochlear nucleus potentials (DNAPs) by a specially designed DNAP electrode placed directly on the brainstem is described. The system is denominated "(cerebellopontine angle) CPA Master" and is designed for hearing preservation surgery in the cerebello-pontine angle, through the retro-sigmoid or the retro-labyrinthine approach. As an additional novelty within the field, the system allows intraoperative mapping and thus precise localization of the cochlear nerve in its entire trajectory from the brainstem to the fundus of the internal auditory canal, which is a major advance in relation to atraumatic dissection of the nerve. The system can be used for surgery of all types of CPA tumors, for example, vestibular schwannomas, meningiomas and epidermoid cysts, but also for vestibular nerve section and vascular decompression. The system also allows evaluation of the electrical functionality of an anatomically intact cochlear nerve in translabyrinthine surgery, thus predicting the benefit of optional cochlear implantation.