The authors reviewed the diagnostic utility of electrodiagnostic and radiologic data in evaluating 44 patients with lower back pain and radicular symptoms. Electrodiagnostic examination included dermatomal somatosensory evoked potentials of L4, L5, S1 roots stimulating specific sensory nerves. Radiologic examination included the lumbar myelogram and the lumbar spine CT.

Patients were classified into three groups based on their radiological findings: Group 1 had herniated or bulging disc or spinal stenosis with root compression; Group 2 had herniated or bulging disc or spinal stenosis without root compression; Group 3 had normal radiologic findings.

The results were as follows;

1) Electrodiagnostic abnormality rate of the patients in group 1 were 81.8% by needle electromyography and 90.9% by somatosensory evoked potential study.

2) Electrodiagnostic abnormality rate of the patients in group 2 were 58.8% by needle electromyography and 82.4% by somatosensory evoked potential study.

According to the above results, somatosensory evoked potentials are valuable diagnostic tool for the evaluation of radiculopathy, particularly where radiological findings reveal less well-defined evidence for root compression.