ROLE OF THE PREMOTOR CORTEX IN RECOVERY FROM MIDDLE CEREBRAL-ARTERY INFARCTION

Objective: To study the mechanisms underlying recovery from middle cer ebral artery infarction in 7 patients with an average age of 53 years who showed marked recovery of hand function after acute severe hemipar esis caused by their first-ever stroke. Interventions: Assessment of m otor functions, transcranial magnetic stimulation, somatosensory evoke d potentials, magnetic resonance imaging, and positron emission tomogr aphic measurements of regional cerebral blood flow during finger movem ent activity. Results: The infarctions involved the cerebral convexity along the central sulcus from the Sylvian fissure up to the hand area but spared the caudate nucleus, thalamus, middle and posterior portio ns of the internal capsule, and the dorsal part of the precentral gyru s in each patient. After recovery (and increase in motor function scor e of 57%, P < .001), the motor evoked potentials in the hand and leg m uscles contralateral to the infarctions were normal, whereas the somat osensory evoked potentials from the contralateral median nerve were re duced. During fractionated finger movements of the recovered hand, reg ional cerebral blood flow increases occurred bilaterally in the dorsol ateral and medial premotor areas but not in the sensorimotor cortex of either hemisphere. Conclusions: Motor recovery after cortical infarct ion in the middle cerebral artery territory appears to rely on activat ion of premotor cortical areas of both cerebral hemispheres. Thereby, short-term output from motor cortex is likely to be initiated.