The collateral circulation plays a crucial role in maintaining perfusion to brain tissue in ischemic stroke, which prolongs the time window for effective therapies to be provided and ultimately avoids irreversible damage that may lead to worse clinical outcomes. The understanding of this complex vascular bypass system has advanced greatly in the past few years, yet effective treatments for its potentiation as a therapeutic target remain a challenge. The assessment of the collateral circulation is now part of the routine neuroimaging protocols for acute ischemic stroke, which provides a more complete pathophysiological picture in each patient that allows for a better selection for acute reperfusion therapies and a more accurate prognostication of outcomes, among other potential uses. In this review, we aim to provide a structured and updated approach to the collateral circulation while highlighting ongoing research areas with promising future clinical applications.

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BACKGROUND AND PURPOSE: Thrombolysis >4.5 hours after ischemic stroke onset is unproven. We assessed the feasibility of tenecteplase (TNK) treatment in patients with evidence of an ischemic penumbra 4.5 to 24 hours after onset. METHODS: Acute ischemic stroke patients underwent perfusion computed tomography (CT)/magnetic resonance imaging. Patients with cerebral blood volume (CBV) or diffusion weighted imaging Alberta Stroke Program Early CT Scores (ASPECTS) >6 and mismatch score >2 (defined as >2 ASPECTS regions with delay on mean transit time maps and normal CBV) were eligible for treatment with TNK (0.25 mg/kg). Patients with mismatch patterns enrolled in non-endovascular/non-thrombolysis trials and those without mismatch patterns served as comparators. RESULTS: The median (interquartile range) baseline National Institutes of Health Stroke Scale (NIHSS) in TNK treated patients (n=16) was 12 (range, 8 to 15). In the untreated mismatch (n=18) and nonmismatch (n=23) groups, the baseline NIHSS was 12 (range, 7 to 12) and 16 (range, 8 to 20; P=0.09) respectively. There was one symptomatic hemorrhage each in the TNK group (parenchymal hematoma [PH] 2) and non-mismatch group (PH 2). Penumbral salvage volumes were higher in TNK treated patients (48.3 mL [range, 24.9 to 80.4]) than the non-mismatch (–90.8 mL [range, –197 to –20]; P < 0.0001) patients. CONCLUSIONS: This prospective, non-randomized study supports the feasibility of TNK therapy in patients with evidence of ischemic penumbra 4 to 24 hours after onset.
Alberta ; Blood Volume ; Diffusion ; Hematoma ; Hemorrhage ; Humans ; National Institutes of Health (U.S.) ; Perfusion ; Prospective Studies ; Stroke

Background: and Purpose There are reports of decline in the rates of acute emergency presentations during coronavirus disease 2019 (COVID-19) pandemic including stroke. We performed a meta-analysis of the impact of COVID-19 pandemic on rates of stroke presentations and on rates of reperfusion therapy. Methods: Following the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines, we systematically searched the literature for studies reporting changes in stroke presentations and treatment rates before and during the COVID-19 pandemic. Aggregated data were pooled using meta-analysis with random-effect models. Results: We identified 37 observational studies (n=375,657). Pooled analysis showed decline in rates of all strokes (26.0%; 95% confidence interval [CI], 22.4 to 29.7) and its subtypes; ischemic (25.3%; 95% CI, 21.0 to 30.0), hemorrhagic (27.6%; 95% CI, 20.4 to 35.5), transient ischemic attacks (41.9%; 95% CI, 34.8 to 49.3), and stroke mimics (45.6%; 95% CI, 33.5 to 58.0) during months of pandemic compared with the pre-pandemic period. The decline was most evident for mild symptoms (40% mild vs. 25%–29% moderate/severe). Although rates of intravenous thrombolytic (IVT) and endovascular thrombectomy (EVT) decreased during pandemic, the likelihood of being treated with IVT and EVT did not differ between the two periods, both in primary and in comprehensive stroke centers (odds ratio [OR], 1.08; 95% CI, 0.94 to 1.24 and OR, 0.95; 95% CI, 0.83 to 1.09, respectively). Conclusions Rates of all strokes types decreased significantly during pandemic. It is of paramount importance that general population should be educated to seek medical care immediately for stroke-like symptoms during COVID-19 pandemic. Whether delay in initiation of secondary prevention would affect eventual stroke outcomes in the long run needs further study.

Background: and Purpose Although onset-to-treatment time is associated with early clinical recovery in acute ischemic stroke (AIS) patients treated with intravenous tissue plasminogen activator (tPA), the effect of the timing of tPA-induced recanalization on functional outcomes remains debatable. Methods: We conducted a multicenter, prospective observational cohort study to determine whether early (within 1-hour from tPA-bolus) complete or partial recanalization assessed during 2-hour real-time transcranial Doppler monitoring is associated with improved outcomes in patients with proximal occlusions. Outcome events included dramatic clinical recovery (DCR) within 2 and 24-hours from tPA-bolus, 3-month mortality, favorable functional outcome (FFO) and functional independence (FI) defined as modified Rankin Scale (mRS) scores of 0–1 and 0–2 respectively. Results: We enrolled 480 AIS patients (mean age 66±15 years, 60% men, baseline National Institutes of Health Stroke Scale score 15). Patients with early recanalization (53%) had significantly (P<0.001) higher rates of DCR at 2-hour (54% vs. 10%) and 24-hour (63% vs. 22%), 3-month FFO (67% vs. 28%) and FI (81% vs. 39%). Three-month mortality rates (6% vs. 17%) and distribution of 3-month mRS scores were significantly lower in the early recanalization group. After adjusting for potential confounders, early recanalization was independently associated with higher odds of 3-month FFO (odds ratio [OR], 6.19; 95% confidence interval [CI], 3.88 to 9.88) and lower likelihood of 3-month mortality (OR, 0.34; 95% CI, 0.17 to 0.67). Onset to treatment time correlated to the elapsed time between tPA-bolus and recanalization (unstandardized linear regression coefficient, 0.13; 95% CI, 0.06 to 0.19). Conclusions Earlier tPA treatment after stroke onset is associated with faster tPA-induced recanalization. Earlier onset-to-recanalization time results in improved functional recovery and survival in AIS patients with proximal intracranial occlusions.