Evoked Potentials – Patient Information
- What are evoked potential tests?
The evoked potential tests are electrical tests which test the function and integrity of nerves and pathways which transmit signals of sesntions of touch, vision and hearing to the brain. These tests are carried out to assess neurological disorders and conditions such as multiple sclerosis. - Why the Evoked Potential tests are carried out?
The VEP test is conducted in order to assess the function of peripheral nerves in the arms and legs and the sensory or motor pathways in brain and spinal cord. These are used to diagnose neurological problems and conditions such as multiple sclerosis. - What are different types of Evoked Potential test?
The main types of evoked responses are following:- Visual Evoked Potential Response (VEP/VER) : This is recorded when eyes and vision is stimulated by visual stimuli such as flashes of light and patterns and recroding signals and brain waves from the surface of the scalp.
- Somatosensory Evoked Response or Potential (SSER/SSEP): This is recorded when peripheral nerves in the arms and legs are stimulated by electrical pulses and signals and brain waves are recorded from the surface of the scalp.
- Motor Evoked Potential (MEP):
These are recorded when part of brain responsible for movements is stimulated by electrical or megnatic pulses and signals are recorded from the surface of the muscles.
- What stimuli are used for the Evoked Potential tests?
- For VEP/VER a screen with a checkerboard pattern or flashes of light are used to stimulate the eyes and the vision
- For BAEP a cliicking tone or noise is sent through earphone to stimulate ears and hearing
- For SSEP tiny electrical pulses are applied to the peripheral nerves in the arms ( at wrist) and legs ( at ankles).
- From where the responses are recorded?
The brain waves are used to record the above-mentioned responses by connecting electrodes to the head. Recording electrodes and gel are applied to the scalp. The location will be according to the response being recorded. For instance, to record the VER response, the electrodes are placed to the rear of the scalp where the brain registers the visual stimuli. - What to expect during the test?
- You may be asked to provide a consent form before the test.
- Recording electrodes and gel are applied to the scalp. The location will be according to the response being recorded. For instance, to record the VER response, the electrodes are placed to the rear of the scalp where the brain registers the visual stimuli.
- Tell your doctor about any allergies, medication, or health issues if you have any pace makers.
- What involves during the Visual Evoked Potential test?
The test is painless and safe. It requires you to sit straight in a chair as electrodes ( wires) will be attached to your head. You will be asked by the technician to look at the flashing lights or a checkerboard pattern on a screen. The electrodes will pick the tiny electrical signals from your brain and send them to the computer that records the barin waves and the test results are leter generated. These tests will be sent to you the physician or consultant neurophysiologist, who will interpret these results and provide a final report. - What is the approximate time for the VEP test?
It takesaround 30 -40 minutes to conduct the VEP and SSEP tests. - What to do before the test?
- Wear comfortable clothes and avoid jewelry.
- If you wear glasses, bring them with you.
- Shampoo and dry your hair. Make sure there is no spray, gel, or oil on them.
- Keep your hairstyle simple without any braid or intricate hairstyle.
- Keep taking medications prescribed by your doctor.
- Keep the list of medications with you.
- Arrive at least fifteen minutes before your appointment.
- How will I know the test results?
A neurolophysiology consultant physician will interpret all your test results and provide a final report. These results will be sent to your physician. Your physician will communicate the results to you and help you understand them. Call your doctor if you have any questions. - Are there any risks involved with Evoked Potential tests?
The EP tests are generally risk-free procedures. They may cause a little discomfort but are usually harmless. In case the patient has advanced symptoms, they can affect the accuracy of the tests.