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      Impaired Dynamic Cerebral Autoregulation and Cerebrovascular Reactivity in Middle Cerebral Artery Stenosis

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          Abstract

          Purpose

          We sought to investigate the capacity of cerebral autoregulation and cerebrovascular reactivity (CVR) in patients with middle cerebral artery (MCA) stenosis.

          Methods

          Twenty-one patients with MCA stenosis diagnosed by magnetic resonance angiography and 15 healthy controls were enrolled. Cerebral autoregulation was assessed by autoregulatory parameters (rate of recovery/phase/gain) derived from transfer function from spontaneous oscillations of cerebral blood flow velocity and blood pressure. CVR was tested by a rebreathing maneuver.

          Results

          Rate of recovery, phase and CVR estimated from moderate MCA stenosis (rate of recovery  = 17.76±8.21%/s, phase  = 26.93±15.67°, and CVR  = 1.53±0.84%/mmHg, respectively) were significantly different (p<0.05) from controls (rate of recovery  = 39.62±27.99%/s, phase  = 55.66±22.10°, and CVR  = 2.18±0.80%/mmHg, respectively). Rate of recovery (r = −0.698, p<0.001), phase (r = −0.738, p<0.001)) and CVR (r = −0.690, p<0.001) were all significantly correlated with the degree of stenosis.

          Conclusion

          Cerebral autoregulation and CVR were impaired in patients with ≥ 50% MCA stenosis. The measures of both hemodynamic properties were inversely correlated with the stenotic degree.

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          Most cited references 31

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          Global burden of intracranial atherosclerosis.

           Jason K Wong (2006)
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            Severely impaired cerebrovascular reactivity predicts stroke and TIA risk in patients with carotid artery stenosis and occlusion.

            Cross-sectional studies suggest that impaired cerebral haemodynamics is associated with symptomatic status in patients with carotid stenosis and occlusion, but there is relatively little prospective data confirming this association. Transcranial Doppler ultrasonography was used to determine the reactivity of the middle cerebral artery to 8% carbon dioxide in air in 107 patients with either carotid occlusion (n = 48) or asymptomatic carotid stenosis (n = 59). Subjects were followed prospectively until stroke, transient ischaemic attack (TIA), death or study end. Mean duration of follow-up was 635 days. No patients dropped out due to operation before an end-point was reached, or were lost to follow-up. There were 11 ipsilateral ischaemic events during follow-up (six strokes, five TIAs). Exhausted ipsilateral middle cerebral artery reactivity (>20% increase in ipsilateral middle cerebral flow velocity in response to 8% carbon dioxide) predicted ipsilateral stroke and TIA risk in the whole group (P: < 0.00001) and in the carotid occlusion (P: = 0.019) and carotid stenosis (P: = 0.015) groups alone. It also predicted the risk of ipsilateral stroke alone in all three groups. Cox regression was performed, controlling for age, gender, hypertension, diabetes, smoking, ipsilateral CT infarct, degree of contralateral stenosis and the presence of ipsilateral stenosis versus occlusion. Exhausted reactivity remained an independent predictor of ipsilateral stroke and TIA (odds ratio 14.4, 95% confidence interval 2.63-78.74, P: = 0.0021). In contrast, the pulsatility index of the middle cerebral artery was a poor predictor of the risk of stroke. Reactivity to 6% carbon dioxide also predicted the risk of stroke and TIA, but slightly less effectively than reactivity to 8% carbon dioxide. Severely reduced cerebrovascular reactivity predicts the risk of ipsilateral stroke and TIA in patients with carotid occlusion, and to a lesser extent in asymptomatic carotid stenosis. Particularly in the former group, a study is required to determine whether revascularization reduces the risk of stroke in patients with exhausted reactivity.
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              Cerebral autoregulation in stroke: a review of transcranial Doppler studies.

              Cerebral autoregulation may become impaired after stroke. To provide a review of the nature and extent of any autoregulation impairment after stroke and its course over time, a technique allowing repeated bedside measurements with good temporal resolution is required. Transcranial Doppler (TCD) in combination with continuous blood pressure measurements allows noninvasive continuous bedside investigation with high temporal resolution of the dynamic and the steady-state components of cerebral autoregulation. Therefore, this review focuses on all TCD studies on cerebral autoregulation in the setting of documented ischemic stroke. PubMed and EMBASE were searched for studies of stroke, autoregulation, and TCD. Studies were either acute phase ( 96 hours after index stroke) autoregulation studies. Quality of studies was studied in a standardized fashion. Twenty-three studies met the inclusion criteria. General agreement existed on cerebral autoregulation being impaired, even after minor stroke. Bilateral impairment of autoregulation was documented, particularly after lacunar stroke. Studies showed progressive deterioration of cerebral autoregulation in the first 5 days after stroke and recovery over the next 3 months. Impaired cerebral autoregulation as assessed by TCD was related to neurological deterioration, the necessity for decompressive surgery, and poor outcome. Synthesis of the data of various studies was, however, limited by studies not meeting key methodological criteria for observational studies. TCD in combination with continuous blood pressure measurement offers a method with a high temporal resolution feasible for bedside evaluation of cerebral autoregulation in the stroke unit. TCD studies have shown impairment of cerebral autoregulation in various subtypes of ischemic stroke. To improve the synthesis of data from various research groups, there is urgent need for standardization of methodology of TCD studies in cerebral autoregulation.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2014
                4 February 2014
                : 9
                : 2
                Affiliations
                [1 ]Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
                [2 ]Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
                [3 ]Department of Radiology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
                University Medical Center (UMC) Utrecht, Netherlands
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: JC JL WHX SG LYC. Performed the experiments: JC RX JL BH WHX SG. Analyzed the data: JC JL BH. Wrote the paper: JC JL WHX SG.

                Article
                PONE-D-13-40788
                10.1371/journal.pone.0088232
                3913771

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                Page count
                Pages: 6
                Funding
                This study was funded by Innovation Fund of the Chinese Academy of Medical Sciences and Peking Union Medical College (No. 20121002039), ( http://graduate.pumc.edu.cn/). Dr Jia Liu's work was supported by the Natural Science Foundation of China (No. 81000644), ( http://www.nsfc.gov.cn/Portal0/default152.htm). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Research Article
                Biology
                Neuroscience
                Neurophysiology
                Central Nervous System
                Medicine
                Cardiovascular
                Hemodynamics
                Neurology
                Cerebrovascular Diseases
                Neuroimaging
                Radiology
                Diagnostic Radiology
                Ultrasonography
                Interventional Radiology
                Angiography

                Uncategorized

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