Cortical potentials preceding voluntary elbow movement in recovered hemiparesis.

Scalp-recorded movement-related cortical potentials (MRCPs) preceding voluntary elbow flexion were studied in two hemiparetic patients 8 months after a stroke. Both cases had unilateral lenticular and internal capsular vascular lesion sparing the cortex. The motor recovery stage of their paretic arm remained in flexion or extension "synergistic" movements of shoulder, elbow, wrist and fingers. The NS' (negative slope) amplitude preceding voluntary unilateral elbow flexion of the intact arm showed a distinct preponderance over the contralateral precentral area, whereas NS' amplitude preceding flexion of the paretic arm was symmetrically maximal at bilateral precentral areas. It is postulated that the unilateral synergistic elbow flexion of the paretic arm is associated with an activation of bilateral brachial areas of the sensorimotor cortex (SI-MIs), whereas the isolated elbow flexion of the intact arm is associated with an activation of mainly the contralateral SI-MI.