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      Hyperacute Diffusion-Weighted Imaging Abnormalities in Transient Ischemic Attack Patients Signify Irreversible Ischemic Infarction

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          Background: To characterize the frequency and clinical features of diffusion-weighted imaging (DWI) abnormalities in the hyperacute phase of transient ischemic attacks (TIAs). Methods: We performed DWI in 21 consecutive patients with TIA (mean age 64 years; 17 men and 4 women) during both the hyperacute phase (within 6 h after onset) and subacute phase (within 2–9 days after onset). Results: DWI abnormalities were present in the hyperacute phase in 11 patients (positive group) and absent in the other 10 patients (negative group). These groups could not be differentiated based on the clinical characteristics. In the subacute phase, all 11 patients from the positive group had abnormalities on MRI including T<sub>2</sub>-weighted and fluid attenuation inversion recovery images as well as DWI, with lesions being located in regions similar to those observed in the hyperacute phase. Of the 10 patients in the negative group, new DWI abnormalities were noted in 2 during the subacute phase. Conclusions: Approximately half of TIA patients in whom MRI was performed in the hyperacute phase had DWI abnormalities, all of which persisted in the subacute phase. The findings suggest that essentially all hyperacute DWI abnormalities in TIA patients may indicate irreversibility and signify the presence of brain infarction.

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          Most cited references 9

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          Thrombolytic reversal of acute human cerebral ischemic injury shown by diffusion/perfusion magnetic resonance imaging.

          Diffusion magnetic resonance imaging provides an early marker of acute cerebral ischemic injury. Thrombolytic reversal of diffusion abnormalities has not previously been demonstrated in humans. Serial diffusion and perfusion imaging studies were acquired in patients experiencing acute hemispheric cerebral ischemia treated with intra-arterial thrombolytic therapy within 6 hours of symptom onset. Seven patients met inclusion criteria of prethrombolysis and postthrombolysis magnetic resonance studies, presence of large artery anterior circulation occlusion at angiography, and achievement of vessel recanalization. Mean diffusion-weighted imaging lesion volume at baseline was 23 cm3 (95% confidence interval [95% CI], 8-38 cm3) and decreased to 10 cm3 (95% CI, 3-17 cm3) 2.5 to 9.5 hours after thrombolysis. Mean apparent diffusion coefficient lesion volume decreased from 9 cm3 (95% CI, 2-16 cm3) at baseline to 1 cm3 (95% CI, 0.4-2 cm3) early after thrombolysis. A secondary increase in diffusion volumes was seen in 3 of 6 patients at day 7. In all 4 patients in whom perfusion imaging was obtained before and after treatment, complete resolution of the perfusion deficit was shown. Diffusion magnetic resonance signatures of early tissue ischemic injury can be reversed in humans by prompt thrombolytic vessel recanalization. The ischemic penumbra includes not only the region of diffusion/perfusion mismatch, but also portions of the region of initial diffusion abnormality.
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            Effect of intravenous thrombolysis on MRI parameters and functional outcome in acute stroke <6 hours.

            The goals of this study were to examine MRI baseline characteristics of patients with acute ischemic stroke (AIS) and to study the influence of intravenous tissue plasminogen activator (tPA) on MR parameters and functional outcome using a multicenter approach. In this open-label, nonrandomized study of AIS patients with suspected anterior circulation stroke, subjects received a multiparametric stroke MRI protocol (diffusion- and perfusion-weighted imaging and MR angiography) within 6 hours after symptom onset and on follow-up. Patients were treated either with tPA (thrombolysis group) or conservatively (no thrombolysis group). Functional outcome was assessed on day 90 (modified Rankin Score; mRS). We enrolled 139 AIS patients (no thrombolysis group, n=63; thrombolysis group, n=76). Patients treated with tPA were more severely affected (National Institutes of Health Stroke Scale score, 10 versus 13; P=0.002). Recanalization rates were higher in the thrombolysis group (Thrombolysis in Myocardial Infarction criteria 1 through 3 on day 1; 66.2% versus 32.7%; P<0.001). Proximal vessel occlusions resulted in larger infarct volumes and worse outcome (P=0.02). Thrombolysis was associated with a better outcome regardless of the time point of tPA treatment (< or =3 hours or 3 to 6 hours) (univariate analysis: mRS < or =2, P=0.017; mRS < or =1, P=0.023). Age (P=0.003), thrombolytic therapy at 0 to 6 hours (P=0.01), recanalization (P=0.016), lesion volume on day 7 (P=0.001), and initial National Institutes of Health Stroke Scale score (P=0.001) affected functional outcome (mRS on day 90) positively (multivariate analysis). The time point of tPA therapy affected the recanalization rate (P=0.024) but not final infarct volume. In this pilot study, tPA therapy had a beneficial effect on vessel recanalization and functional outcome. Multiparametric MRI delineates tissue at risk of infarction in AIS patients, which may be helpful for the selection of patients for tPA therapy. tPA therapy appeared safe and effective beyond a 3-hour time window. This study delivers the rationale for a randomized, MR-based tPA trial.
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              Detection of diffusion-weighted MRI abnormalities in patients with transient ischemic attack: correlation with clinical characteristics.

              Although diffusion-weighted MRI (DWI) has demonstrated clear superiority over other conventional imaging modalities in the detection of hyperacute cerebral ischemia, its value in the evaluation of patients with transient symptoms has received only limited attention. We assessed the utility of DWI in patients with transient ischemic attack (TIA) to further evaluate the usefulness of this technique in these individuals. A retrospective analysis was performed on all patients entered in the Stanford Stroke Center database during 1997-2001 who were clinically diagnosed with a TIA and who had also undergone a DWI scan or=1 hour, 16 times more likely to have had motor deficits, and 25 times more likely to have had aphasia than patients with negative DWI scans. The combination of all 3 symptoms was 100% specific for an abnormality on DWI. In 7 of 16 cases (44%), a DWI abnormality was present on both DWI and conventional imaging (T2-weighted imaging or fluid-attenuated inversion recovery [FLAIR]). In all of these cases the DWI clarified the extent or acuity of the lesion (n=7) or identified additional lesions not detected by conventional imaging (n=9). In TIA patients, symptom duration >or=1 hour, motor deficits, and aphasia were each independently correlated with detecting an abnormality with DWI. DWI was also helpful in differentiating between chronic versus acute lesions. These data may be of value in identifying those TIA patients for whom MRI evaluation with DWI is of greatest clinical utility.

                Author and article information

                Cerebrovasc Dis
                Cerebrovascular Diseases
                S. Karger AG
                June 2005
                23 June 2005
                : 19
                : 6
                : 362-368
                aStroke Center, Saiseikai Kumamoto Hospital, bCerebrovascular Division, Department of Medicine, Kawasaki Medical School, and cDepartment of Neurology, Kumamoto University School of Medicine, Kumamoto, Japan
                85203 Cerebrovasc Dis 2005;19:362–368
                © 2005 S. Karger AG, Basel

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                Page count
                Figures: 1, Tables: 2, References: 23, Pages: 7
                Original Paper


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