[Cochlear damage caused by middle ear surgeries].

A prospective study was set up to study the reaction of the cochlea after the trauma of middle-ear surgery. For this purpose, the bone conduction of 50 patients was tested every day, beginning on the first post-operative day. To collect information on possible damaging mechanisms, three surgical techniques were studied: Stapes surgery with the opening of the inner ear; mastoidectomy with drill-generated noise; tympanoplasty with manipulations at the stapes. The comparison of the bone conduction thresholds with audiometry results after completed healing of the ear, disclosed that even under the ear-packing, bone conduction can give reliable information on cochlea function, if a 10-15 dB variance due to methodological causes is taken into account. Excessive drilling may result in a temporary threshold shift, which has already resolved at the time of unpacking the ear. No signs of hydraulic damage after manipulation at the stapes could be discovered.