25/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Evolution of early ischemic changes on head CT scan Evolution of early ischemic changes over time in a 35-year-old woman who presented with acute aphasia. (A) NCCT at one hour after symptom onset shows loss of gray white matter differentiation in the left frontal and temporal operculum and insular cortex and hypodensity in the lentiform nucleus (ASPECTS was 4 points for involvement of insula, lentiform, M1-3, M5). (B and C) NCCT and CTA-SI at two hours after symptoms onset and IV rtPA administration show more conspicuous hypodensity and mild effacement of cortical sulci compared with https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 26/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate NCCT at one hour after symptoms onset. (D) NCCT at eight hours after symptoms onset shows frank hypodensity in the infarcted areas. The extent of the hypodense areas remains the same but is more conspicuous than prior NCCT studies. CT: computed tomography; NCCT: noncontrast-enhanced computed tomography; ASPECTS: The Alberta Stroke Program Early CT score; CTA-SI: computed tomography angiography source image; IV: intravenous; rtPA: recombinant tissue plasminogen activator. From: Prakkamakul S, Yoo AJ. ASPECTS CT in Acute Ischemia: Review of Current Data. Top Magn Reson Imaging 2017; 26:103. DOI: 10.1097/RMR.0000000000000122. Copyright 2017. Reproduced with permission from Wolters Kluwer Health. Unauthorized reproduction of this material is prohibited. Graphic 121624 Version 2.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 27/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate ASPECTS study form The ASPECTS value is calculated from two standard axial CT cuts: one at the level of the thalamus and basal ganglia (left), and one just rostral to the basal ganglia (right). A: anterior circulation; P: posterior circulation; C: caudate; L: lentiform; IC: internal capsule; I: insular ribbon; MCA: middle cerebral artery; M1: anterior MCA cortex; M2: MCA cortex lateral to insular ribbon; M3: posterior MCA cortex; M4, M5, and M6 are anterior, lateral, and posterior MCA territories immediately superior to M1, M2, and M3, rostral to basal ganglia Reproduced with permission from: Barber, PA, Demchuk, AM, Zhang, J, Buchan, AM. Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy. ASPECTS Study Group. Alberta Stroke Programme Early CT Score. Lancet 2000; 355:1670. Copyright 2000 The Lancet. Graphic 72190 Version 1.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 28/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate ASPECTS study form and MCA variants (A and B) Right hemisphere, observer variations: lower and upper ASPECTS slices show as shaded areas the minimal and maximal variations in size of the cortical areas of the MCA (M1-M6) chosen by six expert observers. Left hemisphere, ASPECTS study form: A = anterior circulation; P = posterior circulation; C = caudate head; L = lentiform nucleus; IC = internal capsule; I = insular ribbon; MCA = middle cerebral artery; M1 = anterior MCA cortex; M2 = MCA cortex lateral to insular ribbon; M3 = posterior MCA cortex; M4, M5, and M6 are anterior, lateral, and posterior MCA territories, respectively, approximately 2 cm superior to M1, M2, and M3, respectively, rostral to basal ganglia. (C and D) Cortical MCA area variations with change of baseline. In the right hemisphere, the baseline is parallel to the inferior OML; in the left hemisphere, the baseline is the superior OML. OML=orbitomeatal line. (E and F) Normal vascular variations in MCA size on the two ASPECTS slices. The right hemisphere shows the larger normal variations described by van der Zwan* (light https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 29/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate shading). The left hemisphere of each shows the smaller, textbook , variations (dark shading). References van der Zwan, A, Hillen, B, Tulleken, AF, et al. Variability of the territories or the major cerebral arteries. J Neurosurg 1992; 77:927. Osborn, AG. Neuroradiology, Mosby, St. Louis 1995. Reproduced with permission from: Pexman, JH, Barber, PA, Hill, MD, et al. Use of the Alberta Stroke Program Early CT Score (ASPECTS) for assessing CT scans in patients with acute stroke. AJNR Am J Neuroradiol 2001; 22:1534. Copyright 2001 American Society of Neuroradiology. Graphic 63480 Version 1.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 30/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Multiphase CTA images (A) Images in a patient with a left M1 MCA occlusion (arrow) and good collaterals (backfilling arteries). (B) Images in a patient with a left M1 MCA occlusion (dashed arrow) and intermediate collaterals. (C) Images in a patient with a right M1 MCA occlusion (arrowhead) and poor collaterals (minimal backfilling arteries). CTA: computed tomography angiography. https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 31/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Reproduced with permission from: Menon BK, d'Esterre CD, Qazi EM, et al. Multiphase CT angiography: A new tool for the imaging tria patients with acute ischemic stroke. Radiology 2015; 275:510. Copyright 2015 RSNA. Graphic 121648 Version 1.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 32/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Classic pattern of DWI-PWI mismatch Representative case with classic pattern of mismatch. (A) Diffusion weighted-image (DWI). (B) DWI abnormal lesion (shown in red) and hypoperfusion lesion (shown in green) superimposed on DWI. (C) DWI abnormal lesion and hypoperfusion lesion with brain image (DWI) removed. PWI: perfusion-weighted image. Reproduced with permission from: Ogata T, Nagakane Y, Christensen S, et al. A topographic study of the evolution of the MR DWI/PWI mismatch pattern and its clinical impact: a study by the EPITHET and DEFUSE Investigators. Stroke 2011; 42:1596. Copyright 2011 Lippincott Williams & Wilkins. Graphic 82701 Version 5.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 33/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Brain MRI showing large core-penumbra mismatch on diffusion- and perfusion- weighted sequences in a patient with acute ischemic stroke Diffusion- and perfusion-weighted brain MRI showing a large core-penumbra mismatch in a patient with an acute ischemic stroke. Diffusion-weighted MRI (panel A) indicates the infarction core in red as tissue with apparent diffusion coefficient <620 that measures 17 mL in volume. Perfusion-weighted MRI (panel B) indicates the ischemic penumbra in green as tissue with T volume. The mismatch volume is 122 mL and the mismatch ratio is 8.2. >6.0 seconds that measures 139 mL in max MRI: magnetic resonance imaging. Glenn A Tung, MD, FACR. Graphic 129431 Version 2.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 34/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Brain MRI showing a small core-penumbra mismatch on diffusion- and perfusio weighted sequences in a patient with acute ischemic stroke Diffusion- and perfusion-weighted brain MRI showing a small core-penumbra mismatch in a patient with an acute ischemic stroke. Diffusion-weighted MRI (panel A) indicates the infarction core in red as tissue with apparent diffusion coefficient <620 that measures 151 mL in volume. Perfusion-weighted MRI (panel B) indicates the ischemic penumbra in green as tissue with Tmax >6.0 seconds that measures 177 mL in volume. The mismatch volume is 26 mL and the mismatch ratio is 1.2. MRI: magnetic resonance imaging. Glenn A Tung, MD, FACR. Graphic 129434 Version 2.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 35/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate MRI showing DWI-FLAIR mismatch in acute ischemic stroke due to left middle cerebral artery occlusion A 49-year-old woman presented with right hemiplegia and dysarthria. The patient arrived at the emergency department 72 minutes after symptom detection. Her initial NIHSS score was 13. Brain MRI showed an acute ischemic lesion in the left MCA territory on DWI (A and B) without parenchymal signal changes on FLAIR (C and D). MRA showed occlusion of the M1 segment of the left MCA with collateral blood flow in the distal cerebral artery territory (E). Intravenous thrombolysis was started 140 minutes after symptom detection. On DSA, the left MCA was still occluded on the M1 segment (F) and was recanalized after mechanical thrombectomy with a TICI score of 3 (G). Time from symptom detection to recanalization was 189 minutes (3 hours and 9 minutes). The mRS score at three months was 0. NIHSS: National Institutes of Health Stroke Scale; MRI: magnetic resonance imaging; MCA: middle cerebral artery; DWI: diffusion-weighted imaging; FLAIR: fluid-attenuated inversion recovery; MRA: magnetic resonance angiography; DSA: digital subtraction angiography; TICI: thrombolysis in cerebral infarction; mRS: modified Rankin scale. https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 36/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Used with permission of the American Society of Neuroradiology, from: Mourand I, Milhaud D, Arquizan C, et al. Favorable bridging therapy based on DWI-FLAIR mismatch in patients with unclear-onset stroke. AJNR Am J Neuroradiol 2016; 37:88; permission conveyed through Copyright Clearance Center, Inc. Copyright 2016. Graphic 129421 Version 1.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 37/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Indications for mechanical thrombectomy to treat patients with acute ischemic IV: intravenous; tPA: tissue plasminogen activator (alteplase or tenecteplase); CTA: computed tomography an artery occlusion; MT: mechanical thrombectomy; ASPECTS: Alberta Stroke Program Early CT Score; NIHSS: Na tomography; MRI: magnetic resonance imaging; mRS: modified Rankin Scale; MCA: middle cerebral artery; IC recovery. Patients are not ordinarily eligible for IV tPA unless the time last known to be well is <4.5 hours. However, im that is diffusion positive and FLAIR negative) is an option at expert stroke centers to select patients with wake associated UpToDate topics for details. Usually assessed with MRA or CTA, less often with digital subtraction angiography. There is intracranial arterial occlusion of the distal ICA, middle cerebral (M1/M2), or anterior cerebral (A1/A2 MT may be a treatment option for patients with acute ischemic stroke caused by occlusion of the basilar ar stroke centers, but benefit is uncertain. [1] Based upon data from the Aurora study . Reference: https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 38/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate 1. Albers GW, Lansberg MG, Brown S, et al. Assessment of Optimal Patient Selection for Endovascular Thrombectomy Beyond 6 Hou Neurol 2021; 78:1064. Graphic 117086 Version 3.0 https://www.uptodate.com/contents/neuroimaging-of-acute-stroke/print 39/40 7/5/23, 12:16 PM Neuroimaging of acute stroke - UpToDate Contributor Disclosures Jamary Oliveira-Filho, MD, MS, PhD No relevant financial relationship(s) with ineligible companies to disclose. Maarten G Lansberg, MD, PhD No relevant financial relationship(s) with ineligible companies to disclose. Scott E Kasner, MD Grant/Research/Clinical Trial Support: Bayer [Stroke]; Bristol Meyers Squibb [Stroke]; Medtronic [Stroke]; WL Gore and Associates [Stroke]. Consultant/Advisory Boards: Abbvie [Stroke]; AstraZeneca [Stroke]; BMS [Stroke]; Diamedica [Stroke]; Medtronic [Stroke]. All of the relevant financial relationships listed have been mitigated. Glenn A Tung, MD, FACR No relevant financial relationship(s) with ineligible companies to disclose. John F Dashe, MD, PhD No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. 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