Somatosensory evoked potential to peroneal nerve stimulation in patients with herniated lumbar discs.

The somatosensory evoked potential (SEP) to peroneal nerve stimulation was recorded from 76 patients with myelographically proven herniated lumbar disc and was compared with normative data obtained from 65 healthy subjects. All patients with disc herniation had an abnormal SEP even when examination failed to disclose sensory deficits. In the patients with distortion of a root sleeve, the SEP abnormality was confined to the involved side. When myelography demonstrated large defects in the dural sac, there was electrophysiological evidence of disturbed conduction from the asymptomatic leg also. SEP changes in postoperative examinations correlated well with improvement or worsening of the patient's condition and enabled objective evaluation of the dynamics of sensory conduction along the involved structures.