What are evoked potentials?
Evoked potentials are a set of tests, which measure impulses travelling through the
In order to carry out these investigations, electrodes need to be connected to your
head, neck, shoulders and legs, depending upon which tests are being carried out.
The test recommended for you by your consultant will be highlighted or ticked below:
Visual evoked potential (VEP)
Please bring spectacles if you normally wear them.
A visual acuity eye test will be carried out firstly – which entails you reading a wall
chart approximately 6 metres away.
5 electrodes will be placed on your head. You will be asked to concentrate on the
centre of a television screen that has black/white checks. Each eye will be tested in
turn. You may be shown a flashing lamp at the end.
- Time length of test: Between 20 to 45 minutes.
Brainstem Auditory Evoked Potentials (BAEP)
Electrodes are placed behind each ear and one on top of the head. Headphones are
placed over the ears and a clicking noise will be heard. Each ear will be tested in
- Time length of test: Between 20 to 30 minutes.
Somatosensory Evoked Potentials (SSEP)
An impulse is passed through the wrist, which will make your thumb twitch. The
response will be monitored from the electrodes at your shoulder, neck and head.
In the same way as for the arms, an impulse will be passed through your ankle to
make your big toe twitch. This response is monitored from your head and leg.
- Time length of test: Between 30 to 60 minutes for arms or legs in total.
A consultant neurophysiologist will interpret the recording. The results will be
forwarded onto your referring consultant physician. If you wish to make further enquiries, you may contact a technician directly on 01642 282755.