Auditory brainstem response equipment being operated by an audiologist. This equipment measures auditory brainstem response (ABR) by supplying auditory stimuli to the ears in the form of clicks from an earphone (not seen). The resulting neural activity in the auditory brainstem is measured through surface electrodes on the scalp and ear lobes (not seen). ABR audiometry is used to screen for retrocochlear diseases (diseases of the acoustic or eigth cranial nerve). For example, acoustic neuroma (vestibular schwannoma), which is a benign tumour of the myelin sheath surrounding the acoustic nerve.