Somatosensory-evoked potentials in lumbar nerve root decompression.

The adequacy of decompression of nerve roots is determined by direct visual observations and by correlation with roentgenograms of the pathological lesion. The usefulness of additional evidence of adequate neural decompression from intraoperative somatosensory-evoked potential (SEP) data was tested in 41 cases of a herniated intervertebral disc (27 patients) or spinal stenosis (14 patients). Postoperative observations at three weeks and three months were evaluated by intraoperative observation of decreased latency and/or increased amplitude of SEP recordings. In patients with unilateral or asymmetrical bilateral radiculopathy, the asymptomatic or less-affected leg acted as a control in the study. Successful function correlated significantly with intraoperative changes in latency toward normal in the more-affected leg, whether the lesion was herniated nucleus pulposus or spinal stenosis. Intraoperative physiological testing (SEP) is valuable for determining the adequacy of lumbar nerve root decompression and for the prediction of the successful relief of symptoms.