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Somatosensory evoked potential

Your Consultant would like you to have a somatotosensory evoked potential investigation (SEP).

What is a somatosensory evoked potential (SEP)?

This is a test that records the function of a nerve pathway between a limb and the brain by stimulating either a hand or foot depending on your symptoms. Recording this information will assist your consultant in the diagnosis or management of your complaint or condition to allow them to decide on an appropriate treatment plan for you.

A Clinical Physiologist will perform the test and staff in training may be present during your investigation. This will be explained at the time of your appointment
and consent for this will be discussed with you

What should I do before the test?

Please ensure your hair is clean and do not use any products, such as gel or hairspray Continue to take your medication as normal and please bring along a list of your current medication with you. Please wear comfortable loose fitting clothing. You are welcome to bring a friend or relative to accompany you to your appointment.

What will happen during the test?

The Clinical Physiologist performing the SEP will fully explain the test and obtain your consent to continue. They will also obtain a clinical history from you before the test. Depending on your symptoms either your arms and/or legs will be tested. Studies on your arm involve small electrodes being placed on your head, neck, shoulder and wrist using a sticky paste. For leg studies small sticky electrodes will be placed on your head, lower back and ankle using a paste. To test the pathway a nerve in your hand or foot will be stimulated with a small electrical pulse given to the skin at the wrist or ankle which will make the muscle twitch slightly. This will last for about two minutes. During the test you will be asked to relax. During stimulation you may feel a tingling or pulsing. This can be an unusual sensation and should not be painful but may produce mild discomfort. This will be repeated on the opposite arm or leg (depending on symptoms). The whole test may take up to two hours.

What happens after the test?

After the recording the small electrodes will be taken off with warm water. There are no after effects from this test. The results will go back to your consultant for the test within two to three weeks.

Are there any risks?

Please tell the Clinical Physiologist if you have a pacemaker or implanted device fitted, it’s usually still safe to have the test but please bring details of your pacemaker with you to discuss prior to the test. If you have a cardiac defibrillator fitted you must telephone the department to discuss this prior to your appointment date as the test may not be able to go ahead.

If you are unable to attend this appointment, have any specific requirements or questions (before or after this test) please ring 0151 556 3416 as soon as possible. We can provide this information leaflet in larger fonts or audio format via email if required, please phone the number above.

Further information about SEP is available from numerous organisations including:
1. The Brain Charity: 0151 298 2999 or visit or if you live locally call into their library at Neurosupport, Norton Street. Liverpool. L3 8LR

2. The Association of Neurophysiological Scientists:

  • Last Updated:
    01 October 2022
  • Review Date:
    01 October 2026
  • Author:
    SSEP Patient Information
  • Summary:

    Your Consultant would like you to have a somatotosensory evoked potential investigation (SEP).

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