Can an operation of deaf ear be dangerous for hearing?

After a single or modified radical mastoidectomy the hearing of the contralateral ear was followed by pure tone audiometry in 55 patients. In 12 patients a sensorineural--mostly high tone--hearing loss of at least 20 dB was found in the contralateral ear. In six cases this was persistent. The number of patients with hearing loss increased with increasing operation time. The cause of this hearing loss must be the noise of the bone-cutting burr.