Department of Neurology
Department of Neurosurgery
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Somatosensory Evoked Potential Test (SEP)
University of Iowa Department of Neurology
Peer Review Status: Internally Peer Reviewed
Creation Date: 1999
Last Revision Date: March 2004
An SEP test studies the relay of body sensations to your brain and how the brain receives those sensations. A stimulating electrode is placed on your arm or leg, and it generates an electrical signal. Recording electrodes are placed on your head and/or spine. The information received from these electrodes can help to diagnose your problem.
What is it?
- The test evaluates the health of your peripheral nerves and your spinal cord.
- It tests how your spinal cord and/or brain transmits information about body sensations through your peripheral nerves.
- It can localize a "signal blockage" either in the relay system (your peripheral nerves act like telephone wires) or in the interpretive center (your brain and spinal cord act like a telephone receiver).
How long does it take?
Why is an SEP performed?
- It is used if you are experiencing numbness anywhere, muscle weakness, loss of vibration and position sense, or symptoms following spinal or head injury.
Does it hurt?
- No. During the test your muscles may tingle and twitch, but you will not experience any pain.
- The SEP is not a shock treatment.
Where is it conducted
- The EEG and Evoked Potential Labs.
- The Lower Level of Carver Pavilion.
How many SEPs are conducted each year?
What should you do to prepare for the test?
- Eat normal meals.
- You may continue taking prescribed medications unless your doctor gives other instructions.
How is the SEP performed?
- You will recline in a comfortable chair and be asked to remain very still.
- A technologist will glue or tape "recording electrodes" on your head, neck, back, or legs. One or two "stimulating electrodes" are also placed on your arm or leg.
- Each electrode is checked with a meter to ensure proper functioning.
- A pulsing stimulus will start in one of the stimulating electrodes.
- Each time a different area is tested, the pulsing will be started again.
- Each area tested will take 10 to 15 minutes.
Following the test
- The electrodes will be removed with acetone, which dissolves the glue and leaves your hair and skin intact.
- You may return to your hospital room, or go home, unless given other instructions from the doctor.
- You may wash your hair if you wish.
- You will learn the test results either from the doctor on the day of the visit, or from a copy of the letter sent to your personal physician.