Dr. Elizabeth Erickson O'Neill, CCC-A, CISC

• Visual evoked potential, which tests how the brain reacts to visual stimuli. During the test, electrodes will be applied on the scalp and patients are shown a flashing checkerboard pattern. The electrical signals the patients' brain produces in response to the pattern will be recorded. This test is able to identify issues in the optic nerve and is a helpful tool in diagnosing multiple sclerosis, as optic nerve damage is an early sign of that disease.
• Auditory evoked potential, which measures how the brain responds to sound. In this test, the electrodes will be applied on the earlobes and on the scalp. Different sounds, such as clicks and tones, will be played through headphones, and responses to those sounds will be recorded. Aside from hearing loss in children, this test also diagnoses acoustic neuromas, which are noncancerous tumors in the ear canal that affect hearing and balance.
• Somatosensory evoked potential, which tests how well the brain communicates with the spinal cord and the rest of the body. Faint electrical signals will be sent through electrodes that are applied on the wrist or the back of the knee. Electrodes on the scalp will measure how long it takes for the brain to receive the signals. This evoked potential test is often used to diagnose multiple sclerosis. In addition, since it can identify spinal cord issues, it may also be given to individuals who experience numbness following a spinal injury.
• Motor evoked potential, which measures how the motor pathways function. These pathways deliver signals from the brain and spinal cord to the motor neurons, which are specialized cells directly responsible for controlling muscles. The test uses a device to send magnetic or electrical pulses to any part of the body. Patient response will show if motor neurons can adequately receive signals from the brain and spinal cord. Because this test detects communication issues in the motor pathways, it is used to diagnose multiple sclerosis, as well as to evaluate stroke recovery.

Each test takes between 30 to 60 minutes to complete, and can be done at the doctor's office. Application and removal of the electrodes do not hurt, but since they are placed on the scalp, patients should wash their hair with shampoo and avoid using conditioner or other hair products prior to the test.