The use of somatosensory evoked potentials in the evaluation of the central nervous system

SEPs may be recorded over the spine and scalp to stimulation of any accessible mixed or sensory nerve in the extremities. SEP abnormalities are useful in detecting lesions in central somatosensory pathways. They do not establish a specific diagnosis, but they may suggest or support a diagnosis made on clinical grounds. They have been used particularly to detect subclinical lesions in multiple sclerosis, but their role in following the course of this disorder is unclear. SEPs have been used as a prognostic guide in patients with hemispheric stroke and in patients who are comatose following head injury or severe cerebral anoxia; in such instances, however, the SEP often adds little to what can be determined by clinical examination. Their role in the evaluation of patients with brain death is controversial. Preserved SEPs or their early return after a spinal injury suggests an incomplete lesion, and therefore a better prognosis than otherwise. SEPs have been used to minimize or prevent intraoperative neurologic complications by monitoring spinal cord function, but their role in this regard awaits adequate validation. In patients with cervical spondylosis, SEPs elicited by stimulation of a nerve in the lower extremities may be helpful in indicating which patients are liable to develop a significant cord deficit, so that surgical treatment can be considered at an early stage. SEP abnormalities have been described in a number of other neurologic contexts, but the findings may be of more academic than clinical relevance in that they help to define the extent of neuropathologic involvement without altering the management of individual patients.