Postural effects on brain hemodynamics in unilateral cerebral artery occlusive disease: A positron emission tomography study

To investigate effect of assuming of upright posture on brain hemodynamics in patients with unilateral internal carotid or middle cerebral artery occl usion (MCAO), local tissue oxygen extraction fraction (OEF), and postural c hanges in regional cerebral blood flow (rCBF) during supine and sitting con ditions were examined using positron emission tomography (PET) with O-15-ga s steady-state method and H-2 O-15 autoradiographic method. A total of 22 m inor stroke patients at relatively early stages participated. The regions o f interest method was used for analyzing levels of perfusion and oxygen met abolic parameters, and postural rCBF change within MCAO group was investiga ted using statistical parametric mapping. Region of interest analyses showe d significant rCBF reduction in the cortical and subcortical regions distal to the artery occlusion in CAO patients during sitting. Regression analyse s showed that magnitudes of rCBF reduction in those areas were correlated p ositively with OEF values and inversely with metabolic rates of oxygen (P < 0.05). Statistical parametric mapping for MCAO patients demonstrated furth er rCBF reduction by sitting in the occlusion-side MCA territory. The curre nt study suggested that assumption of upright posture could exert an advers e effect on local perfusion in hemodynamically compromised patients with ma jor cerebral vessel occlusion, possibly caused by impairment of local autor egulation.