As your body experiences light, sound, touch, and other sensations, your brain takes in that information as a series of electrical signals. If you have multiple sclerosis (MS), the disease causes damage to your nerves that may slow down, garble, or stop this activity entirely. Evoked potential tests can help doctors see if this is happening to you.
The tests measure the electrical activity in parts of the brain caused by light, sound, and touch. They can help doctors diagnose someone with MS because they can detect problems along some nerves that are too subtle to find through other exams.
There are three main types of evoked potential tests:
- Visual evoked potentials (VEP): You sit in front of a screen and watch an alternating checkerboard pattern.
- Brainstem auditory evoked potentials (BAEP): You hear a series of clicks in each ear.
- Sensory evoked potentials (SEP): You get short electrical pulses on one of your arms or legs.
A fourth type of test, motor evoked potentials, can find damage along nerves in the brain and spinal cord that make your body move. But doctors don’t usually use this type to diagnose MS.
When you have the tests, you’ll have wires placed on your scalp. It’s safe and painless. It usually takes about 2 hours to do all three types of evoked potential tests. A doctor with special training in these tests will interpret the results.
While evoked potentials can help diagnose MS, they can’t let your doctor know for sure whether the condition is causing problems with the signals in your nerves or if they’re happening because of another health problem. Your doctor will consider the results of these tests along with those of other lab tests and your symptoms before he makes a diagnosis.