Motor behavior in stroke patients with isolated medial frontal ischemic infarction.

Abstract

Current interpretation of hemiparesis in anterior cerebral artery infarction holds that whereas leg weakness correlates with destruction of the corticospinal tract at the paracentral lobe, faciobrachial symptoms indicate extension of the infarct to the upper lateral convexity or to subcortical structures, where the corticospinal tract subserving the arm would be interrupted. We analyzed the motor behavior in eight patients with purely medial hemispheric infarctions who had face, arm, and leg involvement. In addition to careful clinical testing, we performed neuroimaging or pathological studies to exclude the involvement of the primary motor cortex or subcortical structures. Motor function was further tested in three patients by studying the reaction time to an auditory stimulus and by stimulating the motor cortex and the cervical and lumbar spine with a magnetic stimulator. All patients had signs of motor neglect, such as lack of spontaneous movement in the upper limb, unilateral reaction to pain stimuli, clumsy voluntary movements, or motor impairment on bimanual tasks. Electrophysiologically, we found absent or poor voluntary activity in both upper and lower limbs contralateral to the infarction. However, whereas cortical stimulation showed absent responses in the lower limb, it disclosed normal latencies in the upper limb, indicating that the corticospinal tract to paretic muscles of the upper limb was intact. Our findings suggest that faciobrachial symptoms in purely medial hemispheric infarctions in the anterior cerebral artery territory reflect motor neglect caused not by involvement of primary motor pathways but by damage to medial premotor areas.