Dermatomal SEPs--a complementary study in evaluating patients with lumbosacral disc prolapse.

We investigated the value of Dermatomal Somatosensory Evoked Potentials in 24 patients with unilateral radiculopathy due to lumbosacral disk prolapse. All patients had clinical signs and symptoms of disk prolapse and positive findings on neuroradiologic testing. We assessed the latency and the amplitude of the first positive waveform of Dermatomal SEPs, as well as conducting peripheral nerve conduction studies and electromyography. Our studies showed a clear correlation of Dermatomal SEP abnormalities and radiculopathy in up to 83.3% of subjects studied. Use of electromyography testing provided this correlation in about 62.5% of the same subjects. On the basis of these results, we propose that Dermatomal SEPs have value in complementing the routine electrophysiological testing of the patients with radiculopathy and provide a sensitive non-invasive technique for defining the level of disk prolapse.