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"mismatch" between positive DWI and negative FLAIR allows the identification of patients that are highly likely to be within the 3-hour time window. Within the first 6 hours of stroke, the sensitivity of FLAIR sequences for acute ischemic lesions increases with time from symptom onset elapsing, approximating 100% after 3 to 6 hours.

Background and Purpose— Intracerebral hemorrhage represents the most feared complication of treatment with intravenous tissue plasminogen activator. We studied whether perfusion-weighted imaging and diffusion-weighted imaging has the potential to identify patients at risk of severe intracerebral hemorrhage after treatment with intravenous tissue plasminogen activator. Methods— We analyzed data of prospectively studied MRI selected acute ischemic stroke patients treated with intravenous tissue plasminogen activator within 6 hours. All patients were examined by perfusion- and diffusion-weighted imaging ≤6 hours. Perfusion- and diffusion-weighted imaging lesion volumes were calculated. Hemorrhagic transformation was assessed on follow-up CT or MRI and diagnosed as hemorrhagic transformation, parenchymal hemorrhage, or symptomatic intracerebral hemorrhage according to ECASS II criteria. Results— Of 152 patients, hemorrhagic transformation was seen in 60 (39.5%), parenchymal hemorrhage in 15 (9.9%), and symptomatic intracerebral hemorrhage in 4 (2.6%). Multiple logistic regression analysis identified onset to treatment time after 3 to 6 hours ( P <0.001), a larger perfusion-weighted imaging lesion volume ( P =0.002), and, as a tendency, a higher score on the National Institutes of Health Stroke Scale on admission ( P =0.068) as independent predictors of hemorrhagic transformation. Neither MRI lesion volumes nor severity of symptoms, but rather only an older age tended to be associated with parenchymal hemorrhage ( P =0.087). Conclusion— Our results further support the concept of a different pathogenesis for hemorrhagic transformation and parenchymal hemorrhage. Whereas hemorrhagic transformation should be regarded as a clinically irrelevant epiphenomenon of ischemic damage and reperfusion, parenchymal hemorrhage appears to be related to biologic effects of tissue plasminogen activator and other pre-existing pathologic conditions, which deserve further investigation.

Objective:The objectives of this study were to measure the global impact of the pandemic on the volumes for intravenous thrombolysis (IVT), IVT transfers, and stroke hospitalizations over 4 months at the height of the pandemic (March 1 to June 30, 2020) compared with two control 4-month periods.Methods:We conducted a cross-sectional, observational, retrospective study across 6 continents, 70 countries, and 457 stroke centers. Diagnoses were identified by their ICD-10 codes and/or classifications in stroke databases.Results:There were 91,373 stroke admissions in the 4 months immediately before compared to 80,894 admissions during the pandemic months, representing an 11.5% (95%CI, -11.7 to - 11.3, p<0.0001) decline. There were 13,334 IVT therapies in the 4 months preceding compared to 11,570 procedures during the pandemic, representing a 13.2% (95%CI, -13.8 to -12.7, p<0.0001) drop. Interfacility IVT transfers decreased from 1,337 to 1,178, or an 11.9% decrease (95%CI, -13.7 to -10.3, p=0.001). Recovery of stroke hospitalization volume (9.5%, 95%CI 9.2-9.8, p<0.0001) was noted over the two later (May, June) versus the two earlier (March, April) pandemic months. There was a 1.48% stroke rate across 119,967 COVID-19 hospitalizations. SARS-CoV-2 infection was noted in 3.3% (1,722/52,026) of all stroke admissions.Conclusions:The COVID-19 pandemic was associated with a global decline in the volume of stroke hospitalizations, IVT, and interfacility IVT transfers. Primary stroke centers and centers with higher COVID19 inpatient volumes experienced steeper declines. Recovery of stroke hospitalization was noted in the later pandemic months.

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Background and Purpose-Strokes have especially devastating implications if they occur early in life; however, only limited information exists on the characteristics of acute cerebrovascular disease in young adults. Although risk factors and manifestation of atherosclerosis are commonly associated with stroke in the elderly, recent data suggests different causes for stroke in the young. We initiated the prospective, multinational European study Stroke in Young Fabry Patients (sifap) to characterize a cohort of young stroke patients. Methods-Overall, 5023 patients aged 18 to 55 years with the diagnosis of ischemic stroke (3396) *Drs Rolfs, Fazekas and Grittner contributed equally to this work. Authors contributions: Dr Rolfs has conceptualized, initiated, and designed and organized the study, has been involved in the recruitment of the patients, and wrote significant parts of the manuscript. Dr Fazekas was involved in the study planning and has done together with Drs Enzinger and Schmidt the analysis of all MRI scans; this group was mainly involved in the statistical analysis of the MRI data. Drs Martus, Grittner, Holzhausen have taken responsibility for all statistical analysis and for the data structure of the total data bank. Drs Dichgans, Böttcher, Tatlisumak, Tanislav, Jungehulsing, Putaala, Huber, Bodechtel, Lichy, Hennerici, Kaps, Meyer, Kessler have been most active in the recruitment of the patients, drafting the manuscript and significantly influencing the scientific discussion. Dr Heuschmann was involved in drafting the manuscript and influencing the scientific discussion. Dr Norrving chaired the steering and publication committees of sifap, has written parts of the manuscript, and has significantly influenced the scientific discussions. Drs Lackner and Paschke, H. Mascher, Dr Riess have been involved in the laboratory analyses. Dr Kolodny has mostly contributed to the discussion of the Fabry cases. Dr Giese assisted in writing and editing the manuscript. All authors have reviewed, critically revised and approved the final version of the manuscript.The sponsors of the study had no role in the study design, data collection, data analysis, interpretation, writing of the manuscript, or the decision to submit the manuscript for publication. The academic authors had unrestricted access to the derived dataset, and assume full responsibility for the completeness, integrity, and interpretation of the data, as well as writing the study report and the decision to submit for publication.†Listed in Appendix I in the online-only Data Supplement. Jeffrey L. Saver, MD, was guest editor for this article.

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Background: We applied magnetic resonance imaging to analyze the degree of local diffusion and perfusion abnormalities and the status of reperfusion in regions with subsequent hemorrhagic transformation (HT). Methods: 51 patients with acute ischemic stroke were studied by diffusion- and perfusion-weighted imaging within 3.0 ± 0.8 h, on day 1 and days 5–8. After realignment of the image data sets, the parameter maps of the apparent diffusion coefficient (ADC), cerebral blood flow (CBF) and cerebral blood volume (CBV), and mean transit time were analyzed in the area of subsequent HT. The degree of local diffusion and perfusion impairment in the HT area was compared with the entire diffusion and perfusion abnormality. Reperfusion status was separately assessed for the entire perfusion abnormality and the HT area. Results: HT was observed in 19/51 patients (37.2%) within 8 days after symptom onset. Areas destined for HT revealed a more severe decrease in ADC (to 70 ± 13%; p < 0.01), CBV (to 31 ± 26%; p < 0.001) and CBF (to 28 ± 19%; p < 0.001) compared to the entire perfusion abnormality. Local reperfusion in the HT area was seen in 18/19 patients. The presence of HT did not coincide with a worse clinical outcome. Discussion: HT is the result of reperfusion in the region with the most severe local perfusion impairment and does not influence the neurological outcome.