Somatosensory Evoked Potentials (SEPs or SSEPs) measure the electrical response in the brain and spinal cord when a nerve in an arm or leg is stimulated with a small electrical pulseIn multiple sclerosis.  There may be a delay in the passage of the signals up the spinal cord or through the brainstem, this will show up in the test, which may also give information about where in the nervous system this delay has occurred.

The test is also used to help with the diagnosis of a range of other disorders known to produce abnormal SEPs, including being used during spinal surgery to monitor the spinal cord function. This can reduce the risk of serious injury to the spinal cord during this type of operation.