Postural Effects on Brain Hemodynamics in Unilateral Cerebral Artery Occlusive Disease: A Positron Emission Tomography Study

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Abstract
To investigate effect of assuming of upright posture on brain hemodynamics in patients with unilateral internal carotid or middle cerebral artery occlusion (MCAO), local tissue oxygen extraction fraction (OEF), and postural changes in regional cerebral blood flow (rCBF) during supine and sitting conditions were examined using positron emission tomography (PET) with 15O-gas steady-state method and H215O autoradiographic method. A total of 22 minor stroke patients at relatively early stages participated. The regions of interest method was used for analyzing levels of perfusion and oxygen metabolic parameters, and postural rCBF change within MCAO group was investigated using statistical parametric mapping. Region of interest analyses showed significant rCBF reduction in the cortical and subcortical regions distal to the artery occlusion in CAO patients during sitting. Regression analyses showed that magnitudes of rCBF reduction in those areas were correlated positively with OEF values and inversely with metabolic rates of oxygen ( P < 0.05). Statistical parametric mapping for MCAO patients demonstrated further rCBF reduction by sitting in the occlusion-side MCA territory. The current study suggested that assumption of upright posture could exert an adverse effect on local perfusion in hemodynamically compromised patients with major cerebral vessel occlusion, possibly caused by impairment of local autoregulation.