Change of Diagnostic Sensitivity in Dermatomal Somatosensory Evoked Potentials according to Stimulation Intensity in Lumbosacral Radiculopathy

J Korean Assoc EMG Electrodiagn Med 2005;7(1):1-7.
Published online May 10, 2005.

Abstract

Objectives: To evaluate the change of diagnostic sensitivity for the dermatomal somatosensory evoked potential (DSEP) study in the lumbosacral radiculopathy according to stimulation intensities. Method: Seventeen patients with unilateral and unilevel lumbosacral radiculopathy which was confirmed by routine electrodiagnostic study and supported by radiological imaging study and clinical sign were enrolled. Their mean age was 47 years. The DSEP study was performed with stimulation intensity of sensory threshold 1.0, 1.5, 2.0, and 3.0 times to each patients. Stimulation sites were over the dorsum of the foot on the distal fifth metatrsal bone for the S1 dermatome and at the interdigital web space between the first and the second toes for the L5 dermatome. Active recordings were made at Cz’and reference to Fz of scalp. Results: Abnormalities of DSEP study were detected in 15 patients (88%): 86% for the L5 radiculopathy and 100% for the S1 radiculopathy, respectively. The DSEP studies with the stimulation intensity of 1.0 time of sensory threshold were abnormal in 13 patients which included 10 patients with absent evoked potentials. Conclusion: These results demonstrated that the DSEP study with lower stimulation intensity is more sensitive for detecting abnormalities in root function compared with the conventional DSEP study.

Key Words: Dermatomal somatosensory evoked potential study, Lumbosacral radiculopathy, Stimulation intensity