NEURAL ACTIVATION OF THE BRAIN WITH HEMODYNAMIC INSUFFICIENCY

Little is known about how ischemia affects hemodynamic responses to ne ural activation in the brain. We compare the effects of a motor activa tion task and a cerebral vasodilating agent, acetazolamide (ACZ), on r egional cerebral blood flow (rCBF) in primary sensorimotor cortex (PSM ) in six patients with major cerebral artery steno-occlusive lesions w ithout paresis of the upper extremities. Quantitative rCBF was measure d in all patients using (H2O)-O-15 autoradiographic method and positro n emission tomography. The CBF was determined at rest, during a bimanu al motor activation task, and 10 minutes after ACZ administration. Wit h bimanual motor activation, rCBF increased significantly in both PSM compared with at rest (P < 0.01 on lesion side, and P < 0.02 on contra lateral side). However, rCBF did not increase after ACZ injection in t he PSM on the lesion side, whereas rCBF increased significantly in the contralateral PSM after ACZ injection compared with the level at rest . This result suggests that despite a decreased hemodynamic reserve, t here is a nearly normal flow response to neural activation, indicating that the mechanism of vasodilation responsible for perfusion change i s different for acetazolamide and neural activation. The relations amo ng neural activation, hemodynamic status, and cerebral metabolism in t he ischemic stroke patients are discussed.