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The probability of middle cerebral artery MRA flow signal abnormality with quantified CT ischaemic change: targets for future therapeutic studies

¹ Calgary Stroke Program, Department of Clinical Neuroscience, Seaman Family Magnetic Research Centre, 1403-29 St. NW, Calgary, AB, Canada
² Department of Medicine and Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada
³ Department of Clinical Radiology, University of Calgary, Calgary, AB, Canada
⁴ Department of Radiology, University of Calgary, Calgary, AB, Canada

Correspondence to:
Correspondence to:
P A Barber Assistant Professor
Department of Clinical Neurosciences, University of Calgary, Institute for Biodiagnostics (West), Room 153, 3330 Hospital Drive, Calgary, Canada AB T2N 4N1; pabarber{at}ucalgary.ca

Objectives: In this study we define the probability of vascular abnormality in the middle cerebral artery (MCA) territory according to the extent of ischaemic change seen using computed tomography (CT). We assessed the sensitivity and specificity of the hyperdense middle cerebral artery (HMCA) and the "dot" sign using magnetic resonance angiography (MRA).

Methods: Patients presenting with ischaemic stroke had a CT scan (<6 h) prior to MRI (<7 h). A quantitative CT scoring system (ASPECTS) was applied to CT and diffusion weighted images (DWI) at baseline and follow up (24 h) by five independent observers. The presence of HMCA and the MCA "dot" sign was also evaluated. An expert reader assessed the 3D time of flight (TOF) MRA in the anterior circulation for areas of decreased vascular signal in the MCA territory, with an absent signal taken to represent severely reduced or absent flow.

Results: A total of 100 consecutive patients had baseline CT and MR scans. The median NIHSS was 9. The median CT ASPECTS was 8 and equalled the median DWI ASPECTS. There were a total of 10 HMCA and 19 MCA "dot" signs, with four patients having both HMCA and "dot" signs. A total of 47 MRA flow signal abnormalities were observed in the anterior circulation.

Conclusions: In the absence of accessible neurovascular imaging, the extent of CT ischaemia (ASPECTS) is a strong predictor of vascular occlusion. The CT hyperdense artery signs have a high positive predictive value but low negative predictive value.

Abbreviations: ACAs, anterior cerebral artery; ASPECTS, Alberta Stroke Program Early CT Score; BA, basilar artery; CT, computed tomography; DWI, diffusion weighted imaging; FLAIR, fluid attenuated inversion recovery; HMCA, hyperdense MCA; ICA, internal carotid artery; MCA, middle cerebral artery; MRA, magnetic resonance angiography; mRS, modified Rankin scale; NIHSS, National Institute of Health Stroke Scale; PCA, posterior cerebral artery; PROACT-II, ProLyse for Acute Cerebral Thromboembolism trial; tPA, tissue plasminogen activator

Keywords: acute stroke; computed tomography; magnetic resonance angiography; vascular occlusion

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