Brainstem auditory evoked potential is a type of electromyography, which is used to check whether the brainstem function is impaired. During the examination, the patient is asked to wash his hair the day before, and then in a dark room, the patient is instructed to relax and put on headphones to record a series of electrical activities from the scalp to the brainstem through sound stimulation, which mainly reflects the functional status of the auditory conduction pathway and the function of the relevant structures from the cochlea to the brainstem. For example, for demyelinating lesions such as multiple sclerosis, or when we find suspicious signs and symptoms of brainstem lesions and need to examine brainstem function, we can do a brainstem auditory evoked potential. In addition, brainstem auditory evoked potentials can also be used as a criterion in the diagnosis of brain death.