Diagnostic Usefulness of Dermatomal Somatosensory Evoked Potentials by Low Intensity Stimulation in Lumbar Radiculopathy

ABSTRACT

OBJECTIVE: To investigate diagnostic usefulness of dermatomal somatosensory evoked potentials (DSEP) in the evaluation of lumbar radiculopathy using stimulation intensity lower than conventional stimulation intensity. METHOD: Fifty-seven patients with low back pain were studied with DSEP and needle electromyography (EMG). The radiculopathy was diagnosed by lumbar MRI or operative findings. The DSEP study was performed with stimulation intensity of 1.0x, 1.5x, 2.5x sensory threshold, respectively. We compared the sensitivity and specificity of DSEP and needle EMG in the evaluation of L5 radiculopathy. RESULTS: Radiological and operative findings revealed unilateral herniated disc and L5 root compression in 38 patients (66.7%). Nineteen patients had no significant L5 root compression. The sensitivity and specificity of abnormality were 68.4% and 78.9% in 1.0x sensory threshold stimulation; 71.1%, 78.9% in 1.5x sensory threshold stimulation; and 44.7%, 84.2% in 2.5x sensory threshold stimulation, respectively. Whereas they were 55.2% and 100% in needle EMG. CONCLUSION: DSEP using low stimulus intensity showed higher sensitivity in the diagnosis of L5 radilculopathy, and DSEP might provide additional diagnostic usefulness in the evaluation of patients with suspected L5 radiculopathy.