Facilitation Characteristics of Motor Evoked Potentials in Stroke Patients with Subcortical Lesion

J Korean Assoc EMG Electrodiagn Med 2003;5(2):75-81.
Published online May 10, 2003.

Abstract

Objective: To characterize the facilitation response of motor evoked potentials (MEPs) in stroke patients with subcortical lesion and to suggest the useful parameters of MEPs as an objective tool for the motor impairment after stroke. Method: MEPs induced by cortical stimulation were obtained at both thenar muscles in 15 stroke patients with subcortical lesion. Motor cortex was stimulated with 130% intensity of threshold during rest, minimal and moderate voluntary muscle contraction. We analyzed the MEP amplitude or area in 130% threshold intensity at rest (R), on minimal contraction (Fmin), and moderate contraction (Fmax). A ratio of Fmax in both hemispheres (interhemispheric facilitation ratio, FR), a ratio of Fmax to R (facilitation index, FIR), and a ratio of Fmax to Fmin (FIMIN) in each hemisphere were also analyzed. The amplitudes and areas of MEPs were expressed as a ratio to their compound muscle action potentials. Result: 1) Ten subjects had smaller Fmax in the affected side than in the unaffected side, 0.45 0.15 and 0.86 0.30, respectively. Fmax in affected side were larger than those in unaffected in five subjects. 2) FIMIN (Fmax / Fmin) of affected side was significantly smaller than that of unaffected regardless of Fmax or FR, 1.86 0.77 and 1.16 0.32, respectively(p<0.05). Conclusion: FIMIN can be useful parameter as an objective tool indicating the current motor dysfunction in stroke patients because it has a consistent abnormal value in affected side regardless of different pattens of MEP responses.

Key Words: Facilitation, Motor evoked potentials, Subcortical lesion