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Somatosensory Evoked Potential Patient Information Leaflet
Your consultant would like you to have a Somatosensory Evoked Potential in-
We hope that the following information will help to answer any questions you
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.
What should I do before the test?
Please wash your hair and do not use any hair products (gel, hairspray etc).
Take your medication as normal unless otherwise directed by your doctor.
Eat as normal.
Bring a list of medication that you take with you.
Please wear comfortable loose fitting clothing.
What will happen during the test?
It will be necessary for us to obtain consent before your investigation. This will
be done at the beginning of the test.
The clinical physiologist performing the SEP will explain each aspect of the test
and will be happy to answer any questions you may have.
You will be asked to lie on a couch or chair during the test.
The clinical physiologist will measure your head with a tape measure and mark
some points with a skin pencil.
Depending on your symptoms either your arm or leg will be tested.
Studies on your arm involve small electrodes being placed on your head, shoul-
der 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 2 minutes.
During the test you will be asked to relax. During stimulation you may feel a
tingling or pulsing.
This will be repeated on the opposite arm or leg (depending on symptoms).
How will the results of this test assist my consultant?
An SEP will help your consultant in the diagnosis and management of your
complaint or condition.
Are there any risks?
Please tell the doctor if you have a pacemaker or implanted device fitted,
it 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 depart-
ment to discuss as the test may not be performed.
Is an SEP test painful?
Most people say that the electric pulse produces an unusual sensation such
as tingling or pulsing.
How long will the test take?
The whole test will take about 45 minutes.
What are the consequences of not having an SEP?
An SEP is a well established method of helping doctors to diagnose and treat
a wide range of medical conditions. Your doctor would not have as complete a
picture as they require and hence your diagnosis may take longer and/or your
treatment may not be the most appropriate.
Are there any alternative ways of getting the same information that an
No. However, there are many areas of research taking place and the develop-
ment of scanning techniques may mean that in future different methods of
measuring electrical brain activity may be available.
What happens after the test?
After the recording the small electrodes will be taken off with warm water.
You may wish to wash your hair as it will feel a little sticky. Hair washing
facilities are available in the department, you should bring with you
shampoo and a towel if you wish to use this facility.
You will then be able to go home or back to work and carry on as usual.
There are no after-effects from this test.
The results will go back to your consultant for the test within 2 weeks.
If for any reason you are unable to make this appointment or have any
questions please ring 0151 529 5602 as soon as possible.
We welcome feedback about our services. Please tell a member of staff
if you felt this service was good or otherwise.
This information can be translated on request or if preferred an interpreter can
be arranged for additional information regarding these services please contact
the Walton centre on 0151 525 3611
For practical advice our Patient Advice and liaison service (PALS) can be of
assistance. Contact PALS manager Tony Murphy on 0151 529 6100, email
firstname.lastname@example.org or www.thewaltoncentre.nhs.uk
Alternatively, log on to: www.neurosupport.org.uk or call 0151 298 2999 for
advice and information for people with neurological conditions and their car-