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Somato-sensory Evoked Potentials (Lower Limb)

What is a Somato-sensory Evoked Potential?

These are tests of the nerve pathways from the leg through the spinal cord to the brain.  An electrical stimulator is used to pass brief electrical pulses along the nerve.  You will be able to feel the electrical currents as a pulsing/tapping sensation.  You will also get a small twitch of your foot with the pulses. This can be uncomfortable, but should not be painful. There are no after effects.

This test can take 45 to 60 minutes.

How is it performed?

Leads are attached to your knee, back and scalp.  The leads are attached with sticky white paste which will be removed at the end of the test. The tibial nerve in your ankle will be stimulated with the electrical impulse.  The responses are recorded by the leads.  The responses are seen on a screen as wave patterns.

How do I prepare for the test?

Please ensure your hair is clean and free from hairspray and oil. 

If you are taking medication please continue to take it and bring a list of your medication with you.

Continue to eat meals as normal.

There are no side effects from this test.

How long will I have to wait?

You have been given a specific appointment time and patients are usually seen on time.  It is important that you arrive on time.  Please allow plenty of time for parking.

When will I get the results?

The results are sent to the doctor that referred you for the test and are usually available within seven days.


If you have any concerns or questions please speak to one of the physiologists on the number below or when you attend for your appointment.

Neurophysiology Department   01422 222976