Evoked Potential Studies measure electrical activity in the brain in response to stimulation of sight, sound, or touch. Stimuli delivered to the brain through each of these senses evoke minute electrical signals. These signals travel along the nerves and in case of touch through the spinal cord to specific regions of the brain and are picked up by electrodes, amplified, and displayed for a doctor to interpret.
Visual Evoked Potential (VEP) - This test can diagnose problems with the optic nerves that affect sight. Electrodes are placed along the scalp and the electrical signals are recorded as you watch a checkerboard pattern flash for several minutes on a screen.
Auditory Brainstem Response (ABR) - This test can diagnose hearing ability and can point to possible brainstem tumors or multiple sclerosis. Electrodes are placed on the scalp and earlobes. Auditory stimuli, such as clicking noises and tones, are delivered to one ear after another.
Somatosensory Evoked Potential (SSEP) - This test can detect problems with the spinal cord. For this test, electrodes are attached to the wrist, the back of the knee, or other locations. A mild electrical stimulus is applied through the electrodes. Electrodes on the scalp then determine the amount of time it takes for the current to travel along the nerves and spinal cord to the sensation centers in brain.