Somatosensory Evoked Potentials

SSEP studies or SOMATOSENSORY EVOKED POTENTIALS are the evaluation of the central nervous system via sensory tracts in the spinal cord conecting the extremities to the brain. This is the mechanism by which we are able to perceive pain and temperature.

The studies are performed by supplying a nerve in your wrist and/or ankle with a small electrical shock and recording the time it takes for your brain to register that response. This usually takes in the neighborhood of 20 thousandths of a second from the wrist, and 40 thousandths of a second from the ankle. The amplitude of the response is so small that it must be averaged (adding several stimulus responses together in order to obtain one reproducable response). Even after the response is averaged, the amplitude often does not exceed one microvolt, and must therefore be repeated to insure accuracy. Recordings are obtained by placing small electrodes on the scalp over an area called the somatosensory strip (thus the name).

The studies are usually performed in the office, or on occasion, in the operating room when surgery is taking place on or near the spinal cord.

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