Somatosensory evoked potentials (SEPs) are used as an extension of the electrodiagnostic evaluation and nerve conduction tests that are performed in large myelinated sensory fibers of the peripheral and central nervous systems. SEP studies are noninvasive; SEPs are obtained by the repetitive submaximal stimulation of a sensory or mixed sensory/motor peripheral nerve and recording the average responses from electrodes placed over proximal portions of the nerves stimulated in the plexus, spine, and scalp.

Current clinical applications of SEPs assess short latency responses. These are portions of a SEP waveform occurring within 25 ms after stimulation of a nerve at the wrist, 40 ms after stimulation of a nerve at the knee, and 50 ms after stimulation of a nerve at the ankle. The amplitude, peak, and interpeak latency measurements, with side-to-side comparisons, are used to assess abnormalities. Depending on the clinical condition being studied, several nerves in one extremity may have to be tested and the results compared with those for the contralateral limb to assess focal and diffuse disease processes.

SEPs may also be used to assess the functional integrity of central and peripheral sensory pathways. Common conditions in which SEPs have demonstrated usefulness in electrodiagnostic medicine include, but are not limited to, the following: mononeuropathy, polyneuropathy, plexopathy, neuronopathy, radiculopathy, spinal cord trauma, subacute combined degeneration, non-traumatic spinal cord lesions, multiple sclerosis (MS), spinal cerebellar degeneration, myoclonus, coma, and the intraoperative monitoring of peripheral/cranial nerves, the spinal cord, and the brain stem/brain.