Collaterial Flow, A Key Factor To The Outcome Of Atherosclerotic Ischemia Stroke

PART 1 Hyperintense vessels sign on fluid-attenuated inversion recovery imaging and collateral circulation in patients with atherosc- lerotic stenosis or occlusion of middle cerebral artery.Objective: Hyperintense vessels (HV) in lateral fissure and cortical sulci are frequently observed on fluid-attenuated inversion recovery imaging (FLAIR) in acute ischemic stroke patients. However, the background of hemodynamics and clinical implications of this sign have not yet been well defined.The objective of this study was to investigate the features of HV in other Magnetic resonance imaging (MRI) factors and its relevance to perfusion of ischemia zone and clinical outcome in acute ischemic stroke patients. Methods: Prominence and location of HV were documented in 41 consecutive patients with atherosclerotic stenosis or occlusion of middle cerebral arterial stem. Conventional MRI included FLAIR , Gradient recalled echo (GRE) , time-of-flight magnetic-resonance-angiography (TOF MRA) were collected along with Gd contrast-enhanced TOF MRA and perfusion weighted (PW) MRI on a 3.0 tesla system. NIH Stroke Scale (NIHSS) was used as a measure of clinical severity.The graded data of FLAIR HV was correlated with infarct core area and perfusion deficits.Results: HV distal to arterial occlusion was observed in 75.6% of patients. Evidence from multiple MR imaging suggested that the sign of HV attribute to slow colateral flow coming from meningeal vessels . The sign of hyperintense vessels in those patients without recanalization theraphy persistently exist from acute stroke phase to chronic phase without apparent change. The grade of HV was relative to the NIHSS (r=0.26, p=0.04).Conclusion: FLAIR HV represented slow flow of collateral circulation, which was important to sustain perfusion to cortical ischemic territory.PART 2 Collateral circulation and residual perfusion in patients with atherosclerotic stenosis or occlusion of middle cerebral artery and without recanalization therapyObjective: Infarct growth in acute cerebral ischemic stroke can be effected by multhple factors. We supposed collateral flow seems to be substantial factor that correlated with the growth of infarct core and perfusion deficit zone of penumbra.Methods: 41 patients with atherosclerotic stenosis or occlusion of middle cerebral artery and without recanalization therapy were included in this study.Gd contrast enhancement time-of-flight MR angiography was used to evaluate collateral flow grade. Diffusion weighted(DW)and Perfusion weighted ( PW)magnetic resonance imaging, MRI)were used to detect infarct core and perfusion deficit zone. And follow up FLAIR was used to determine the final infarct volumes.Results: In background of stenosis or occlusion of MCA, infarct cores usually located in peripheral region of dital artery ,eg deep white matter of parietal lobe , basal ganglia,and watershed area of cortical, where the collateral flow due to reduction of amount of collatery vessel can not reach amply. The amount of collateral artery in lateral fissure and cortical sulcus was related with the volume of ischemia on DWI( r=0.45,p=0.04) and NIHSS ( r=0.35,p=0.04) .Redistribution of flow was observed in infarct core and PWI deficit region.Conclusion: Collateral circulation and redistribution of residual perfusion played a key role in preventing the growth of infarct core.PART 3 Interpretation perfusion data of flow sensitive alternating inversion recovery (FAIR)imaging with collateral circulaiton in patients with acute artherosclerosis ischemic strokePurpose: A flow sensitive alternating inversion recovery(FAIR)arterial spin labeling(ASL) magnetic resonance (MR) imaging used electromag- netically labeled arterial blood water as a diffusible tracer to noninvasively measure cerebral blood flow (CBF). We hypothesized that FAIR could detect perfusion deficits and perfusion/diffusion mismatches and predict outcome in acute ischemic stroke in combination with collateral flow imaging.Methods: We studied 53 patients with acute ischemic stroke with middle cerebral artery (MCA) stenosis or occlusion within 3 days of symptom onset. FAIR was measured at a 3.0 T MR unit. Collateral vessel imaging , diffusion- weighted images, magnetic susceptibility perfusion-weighted image (PWI) were also obtained. Visual inspection for perfusion deficits, perfusion/ diffusion mismatches, and comparision between FAIR and PWI . Regional CBF values were correlated with the final infarction volume at 60 days, National Institutes of Health Stroke Scale (NIHSS) score on admission and discharge.Results: Interpretable FAIR images were obtained in all patients. 28 patients(52.8%)had hypoperfusion, 15(28.3%)had normal perfusion, and 10(18.8%)had relative hyperperfusion. Diffusion/FAIR mismatches were present in 45 patients. The amount of collateral vessel had a weak relationship with the FAIR CBF in those hypoperfusion patients (r=0.26, p=0.02). Followed imaging showed that the hypoperfusion area encompassing necrosis core usually did not translate to infarction. FAIR CBF in the affected hemisphere correlated with NIHSS (r=0.37, p=0.03, Spearman rank correlation).Conclusions: FAIR provides rapid noninvasive multislice imaging in brain with quantitative regional CBF. Yet it need to combinate with PWI CBV, MTT and collateral flow imaging to depicts perfusion deficits and penumbra of perfusion/diffusion mismatches.