Audiometry and other hearing tests.

Hearing tests of the peripheral auditory system are well established and the pure-tone audiogram is generally regarded as the screening test of choice in adults. It allows the distinction to be made between conductive, i.e., outer- and middle-ear, and sensorineural, i.e., cochlear, hearing loss, and also to describe the configuration of the hearing thresholds in terms of severity and the frequency affected. Electrophysiologic testing with auditory potentials, e.g., the auditory brainstem response, can identify sites of lesion in the eighth nerve, brainstem, and more centrally. However, it is only in the last two decades that a battery of central auditory tests has been established that can probe the central pathways in more details, i.e., when the pure-tone audiogram may be normal, and yet the patient still has symptoms of hearing dysfunction.