Please read this information carefully before coming in for your Somatosensory Evoked Potential (SEP).
What is an SEP?
SEP stands for somatosensory evoked potential. It is a test that assesses the function of the sensory nerve pathways from the arms and legs to the brain, rather than taking images as you would see following a scan. It is a non-invasive procedure, that records the electrical activity of the brain in response to a series of small electrical impulses on your wrists and ankles.
Why do an SEP?
If you are experiencing numbness, weakness, or other problems in your arms and legs you may be referred for a SEP to see if there are any problems affecting your sensory nerve pathways to the brain.
What happens during the test?
The SEP is usually split into 2 tests; an upper limb SEP where your wrist will be stimulated, and a lower limb SEP which involves ankle stimulation.
Each test will take around 45-60 minute. First your head will be measured, then a few small metal discs will be attached to your head, neck, collar bone, stomach, lower back, and behind your knees using a sticky paste, tape and possibly some glue.
Once everything is attached you will be asked to relax comfortably on a couch. Felt, stimulating pads are then attached either to the wrists or ankles. A small electrical impulse will then be applied to each wrist which will cause your thumb to twitch, this will then be repeated on each of your ankles causing your toes to twitch.
The series of impulses will continue for several minutes until all appropriate responses have been collected and recorded on the machine.
After the procedure the metal discs will be removed, and your head will be cleaned with warm water. If glue has been used, then some acetone (nail varnish remover equivalent) will be used to remove the discs.
Preparing for the test
- Wear loose fitting clothing to give easy access to your neck, back, arms, and legs when applying the metal discs.
- You should arrive with clean, dry hair with no grease, gel, wax, or other hair products.
- Continue taking all regular medication and eat as normal before the test.
- You will be asked if you understand this information and whether you consent to the test before we start. At your appointment you are welcome to ask the physiologist doing the test to give you further information or to explain more about the procedure.
Contact details
This information is intended as a guideline only. If you have any further questions about your test (excluding about results) please contact the department on the numbers below and a member of staff will be happy to help.
Your responsibility as a patient
Outpatient services at North Bristol NHS Trust are in great demand. Even so, every week an average of 600 patients fail to attend, which wastes appointments. Please tell us with as much notice as possible if you no longer need your appointment and we can allocate this to another patient.
What if I am unwell or need to change my appointment?
If you have an infectious condition, such as COVID-19, measles, mumps, chickenpox, flu, stomach upset, have head lice, or are unable to attend your appointment for any other reason, please let us know with as much notice as possible so that your appointment can be rescheduled and offered to someone else.
If you want to change the appointment for a second time, we cannot offer you another date unless there are exceptional circumstances.
What if I don’t attend?
We will assume that you no longer require your appointment, and we will not offer you another one. We will write to the consultant/doctor who referred you and inform them that you did not attend.
© North Bristol NHS Trust. This edition published December 2024. Review due December 2027. NBT003746
