brain, spinal cord, and nerve disorders
Tests for Brain, Spinal Cord, and Nerve Disorders
Evoked Responses
For this test, doctors use stimuli for sight, sound, and touch to activate specific areas of the brain, that is, to evoke responses. EEG is used to detect the response evoked by the stimuli. Based on these responses, doctors can tell how well those areas of the brain are working. For example, a flashing light stimulates the retina of the eye, the optic nerve, and the nerve pathway to the back part of the brain where vision is perceived and interpreted. Evoked responses are particularly useful in testing how well the senses are functioning in infants and children. For example, doctors can test an infant’s hearing by checking for a response after a clicking sound is made at each ear. Evoked responses are also useful in identifying the effects of Multiple Sclerosis (MS) and other disorders on areas of the optic nerve, brain stem, and spinal cord. Such effects may or may not be detected by MRI. Evoked responses can also help predict the prognosis for people who are in a coma. If stimuli do not evoke typical brain activity, the prognosis is likely to be poor. 