Evaluation of the Global Auditory Nerve Activity for Exploration of Hearing in Humans

Inclusion Criteria: * 18 - 80 years ( inclusive borders) * patient having to undergo surgery at the level of the ponto-cerebellar angle (microvascular decompression, vestibular neurotomy, tumor resection of the meningioma type or schwannoma) and * Unaffected by neuro-sensory hearing loss, defined by mean auditory thresholds of less than 20 dB in tone audiometry in bone conduction on the side of the ear to be operated (N = 15, Group 1) or * Showing mild to moderate hearing loss defined by average hearing loss (average of 500, 1000, 2000 and 4000 Hz thresholds) greater than 20 dB and less than 55 dB in air conduction threshold tone audiometry (N = 15 Group 2). * Voluntary subjects to participate in the study, * Subjects having signed written consent to participate in the study, * Easily accessible topics. Exclusion Criteria: * Subjects unable to understand the nature and goals of the study and / or having difficulty communicating with the investigator, * Subjects refusing to participate, subjects whose free and informed consent has not been sought, subjects for which a consent form has not been signed, * Subjects for whom there is a contraindication to general anesthesia, * Subjects with a central neurological pathology that can disrupt electrophysiological recordings * Not affiliated to a French social security scheme or not benefiting from such a scheme, * Majors protected by law, * Pregnant women, * deprived of liberty by judicial or administrative decision, * Infectious or inflammatory pathology of the middle ear.