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(Stroke. 2006;37:1418.)
© 2006 American Heart Association, Inc.

Original Contributions

Persistent Infarct Hyperintensity on Diffusion-Weighted Imaging Late After Stroke Indicates Heterogeneous, Delayed, Infarct Evolution

Carly S. Rivers, MSc, PhD; Joanna M. Wardlaw, MBChB, MD, FRCR, FRCP; Paul A. Armitage, PhD; Mark E. Bastin, DPhil; Trevor K. Carpenter, PhD; Vera Cvoro, MBChB, MD, MRCP; Peter J. Hand, MBChB, MD, MRCP Martin S. Dennis, MBChB, MD, FRCP

From the Division of Clinical Neurosciences (J.M.W., P.A.A., M.E.B., T.K.C., V.C., M.S.D.), Western General Hospital, Edinburgh, UK; RMH Stroke Centre (P.J.H.), Department of Neurology, Royal Melbourne Hospital, Victoria, Australia; and Clinical Trials Research Unit (C.S.R.), University of Leeds, United Kingdom.

Correspondence to Professor J.M. Wardlaw, Division of Clinical Neurosciences, Bramwell-Dott Building, Western General Hospital, Crewe Rd, Edinburgh, EH4 2XU, UK. E-mail jmw{at}skull.dcn.ed.ac.uk

Background and Purpose— Some infarcts have persistently hyperintense areas on diffusion-weighted MRI (DWI) even at 1 month after stroke, whereas others have become isointense to normal brain. We hypothesized that late DWI hyperintensity reflected different infarct evolution compared with areas that were isointense by 1 month.

Methods— We recruited patients prospectively with ischemic stroke, performed DWI and perfusion-weighted MRI (PWI) on admission, at 5 days, 14 days, and 1 month after stroke, and assessed functional outcome at 3 months (Rankin Scale). Patient characteristics and DWI/PWI values were compared for patients with or without "still hyperintense" infarct areas on 1-month DWI.

Results— Among 42 patients, 27 (64%) had "still hyperintense" infarct regions at 1 month, mostly in white matter. Patients with "still hyperintense" regions at 1 month had lower baseline apparent diffusion coefficient ratio (ADCr; mean±SD 0.76±0.12 versus 0.85±0.12; hyperintense versus isointense; P<0.05), prolonged reduction of ADCr (repeated-measures ANOVA; P<0.01), no difference in baseline perfusion but delayed normalization of mean transit time (P<0.05) and cerebral blood flow ratios (repeated measures ANOVA; P<0.05), initially more severe stroke, and worse 3-month outcome than patients whose lesions were isointense by 1 month.

Conclusion— The late DWI lesion hyperintensity emphasizes the heterogeneity in temporal evolution of stroke injury and suggests ongoing "ischemia." Lower baseline ADCr precedes delayed perfusion normalization, suggesting that worse cell swelling impedes reperfusion. Further study is required to determine underlying mechanisms and any potential for subacute intervention to improve recovery.

Key Words: cerebrovascular disorders • magnetic resonance imaging • magnetic resonance imaging, diffusion-weighted • magnetic resonance imaging, perfusion-weighted • stroke