***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background and Purpose — The only Food and Drug Administration ( FDA ) -approved treatment for acute ischemic stroke is tissue plasminogen activator ( tPA ) given intravenously within 3 hours of symptom onset . An alternative strategy for opening intracranial vessels during stroke is mechanical embolectomy , especially for patients ineligible for intravenous tPA .  Methods — We investigated the safety and efficacy of a novel embolectomy device ( Merci Retriever ) to open occluded intracranial large vessels within 8 hours of the onset of stroke symptoms in a prospect i ve , nonr and omized , multicenter trial . All patients were ineligible for intravenous tPA .  Primary outcomes were recanalization and safety , and secondary outcomes were neurological outcome at 90 days in recanalized versus nonrecanalized patients . Results — Recanalization was achieved in 46 % ( 69/151 ) of patients on intention to treat analysis , and in 48 % ( 68/141 ) of patients in whom the device was deployed . This rate is significantly higher than that expected using an historical control of 18 % ( P<0.0001 ) . Clinical ly significant procedural complications occurred in 10 of 141 ( 7.1 % ) patients . Symptomatic intracranial hemorrhages was observed in 11 of 141 ( 7.8 % ) patients . Good neurological outcomes ( modified Rankin score ≤2 ) were more frequent at 90 days in patients with successful recanalization compared with patients with unsuccessful recanalization ( 46 % versus 10 % ; relative risk [ RR ] , 4.4 ; 95 % CI , 2.1 to 9.3 ; P<0.0001 ) , and mortality was less ( 32 % versus 54 % ; RR , 0.59 ; 95 % CI , 0.39 to 0.89 ; P=0.01 ) . Conclusions — A novel endovascular embolectomy device can significantly restore vascular patency during acute ischemic stroke within 8 hours of stroke symptom onset and provides an alternative intervention for patients who are otherwise ineligible for thrombolytics Background and Purpose — Endovascular mechanical thrombectomy may be used during acute ischemic stroke due to large vessel intracranial occlusion . First-generation MERCI devices achieved recanalization rates of 48 % and , when coupled with intraarterial thrombolytic drugs , recanalization rates of 60 % have been reported . Enhancements in embolectomy device design may improve recanalization rates . Methods — Multi MERCI was an international , multicenter , prospect i ve , single-arm trial of  thrombectomy in patients with large vessel stroke treated within 8 hours of symptom onset . Patients with persistent large vessel occlusion after IV tissue plasminogen activator treatment were included . Once the newer generation ( L5 Retriever ) device became available , investigators were instructed to use the L5 Retriever to open vessels and could subsequently use older generation devices and /or intraarterial tissue plasminogen activator . Primary outcome was recanalization of the target vessel . Results — One hundred sixty-four patients received thrombectomy  and 131 were initially treated with the L5 Retriever .  Mean age±SD was 68±16 years , and baseline median ( interquartile range ) National Institutes of Health Stroke Scale score was 19 ( 15 to 23 ) . Treatment with the L5 Retriever result ed in successful recanalization in 75 of 131 ( 57.3 % ) treatable vessels and in 91 of 131 ( 69.5 % ) after adjunctive therapy ( intraarterial tissue plasminogen activator , mechanical ) . Overall , favorable clinical outcomes ( modified Rankin Scale 0 to 2 ) occurred in 36 % and mortality was 34 % ; both outcomes were significantly related to vascular recanalization . Symptomatic intracerebral hemorrhage occurred in 16 patients ( 9.8 % ) ; 4 ( 2.4 % ) of these were parenchymal hematoma type II . Clinical ly significant procedural complications occurred in 9 ( 5.5 % ) patients . Conclusions — Higher rates of recanalization were associated with a newer generation thrombectomy device compared with first-generation devices , but these differences did not achieve statistical significance . Mortality trended lower and the proportion of good clinical outcomes trended higher , consistent with better recanalization Background and Purpose — This study evaluated the safety and efficacy of aggressive mechanical clot disruption ( AMCD ) in acute stroke patients with persisting middle cerebral artery ( MCA ) or internal carotid artery ( ICA ) occlusion after thrombolytic therapy .  Methods — Retrospective case series were used from a prospect ively collected stroke data base on consecutive acute ischemic stroke patients treated with intra-arterial ( IA ) thrombolytics and mechanical clot disruption during a 5-year interval .  Thrombolytic dosage , endovascular techniques , immediate and final recanalization rates , symptomatic hemorrhage , mortality , and outcome were determined . Results — Thirty-two patients received AMCD .  Median baseline National Institutes of Health Stroke Scale ( NIHSS ) score was 18 , and median time to initiation of IA treatment was 261 minutes from symptom onset . ICA occlusion was noted in 16 patients and MCA occlusion in 16 patients : 22 received combined IV/IA thrombolytics , 3 received IV thrombolytics , 6 received IA thrombolytics , and 1 patient received no thrombolytics before AMCD . No immediate periprocedural complications were noted . Immediate recanalization was achieved in 38 % ( 50 % MCA , 25 % ICA ) and final recanalization in 75 % ( 88 % MCA , 63 % ICA ) of patients . Favorable outcome occurred in 19 ( 59 % ) patients , symptomatic cerebral hemorrhage in 3 ( 9.4 % ) patients , and mortality in 4 ( 12.5 % ) patients . Conclusion — AMCD can be performed safely with comparable intracerebral hemorrhage and mortality rates to other IA therapies even after use of intravenous thrombolytics in selected patients . Early deployment of this technique leads to immediate recanalization in one third of patients . AMCD may potentially shorten the time to flow restoration and improve overall recanalization rates achieved with IA therapy Background and Purpose — Acute revascularization is associated with improved outcomes in ischemic stroke patients . However , it is unclear which method of intraarterial intervention , if any , is ideal . Numerous case series and cardiac literature parallels suggest that acute stenting may yield high revascularization levels with low associated morbidity . We therefore conducted a Food and Drug Administration-approved prospect i ve pilot trial to evaluate the safety of intracranial stenting for acute ischemic stroke . Methods — Eligibility criteria included presentation ≤8 hours after stroke onset , age 18 years or older , National Institutes of Health Stroke Scale score ≥8 , angiographic demonstration of focal intracerebral artery occlusion ≤14 mm , and either contraindication to intravenous tissue plasminogen activator or failure to improve 1 hour after intravenous tissue plasminogen activator administration . Exclusion criteria included known hemorrhagic diathesis or coagulopathy , platelet count < 100 000 , intracranial hemorrhage , blood glucose level of < 51 mg/100 mL , or CT perfusion imaging demonstrating more than one-third at-risk territory with nonsalvageable brain ( low cerebral blood volume ) . Data are presented as mean±SD . Results — Twenty patients were enrolled ( mean age , 63±18 years;14 women ) . Mean presenting National Institutes of Health Stroke Scale was 14±3.8 ( median 13 ) . Presenting thrombolysis in myocardial infa rct ion score was 0 ( 85 % of patients ) or 1 ( 15 % ) . Recanalization to thrombolysis in myocardial infa rct ion score of 3 ( 60 % of patients ) or 2 ( 40 % of patients ; P<0.0001 ) was achieved . One ( 5 % ) symptomatic and 2 ( 10 % ) asymptomatic intracranial hemorrhages occurred . At 1-month follow-up , a modified Rankin scale score of ≤3 was achieved in 12 of 20(60 % ) patients and a modified Rankin scale score of ≤1 was achieved in 9 of 20 ( 45 % ) patients . Conclusion — This Food and Drug Administration-approved prospect i ve study suggests primary intracranial stenting for acute stroke may be a valuable addition to the stroke treatment armamentarium BACKGROUND AND PURPOSE We prospect ively evaluated the safety of aggressive mechanical disruption of thrombus following full-dose intravenous ( IV ) recombinant tissue plasminogen activator ( rt-PA ) to treat ischemic stroke in 24 patients with an initial National Institutes of Health stroke scale ( NIHSS ) score of > or=10 . METHODS Clinical evaluations were performed at presentation and 24 hours , 7 to 10 days , and 1 to 3 months ( using modified Rankin scale ) after treatment . These end points were compared to matched historical controls treated with IV rt-PA alone . RESULTS Of the 24 patients , mechanical disruption was undertaken in 17 patients with persistent angiographic occlusion using microcatheter exploration ( n= 3 ) , angioplasty ( n= 5 ) , snare maneuvers ( n= 7 ) , and combination of both ( n= 2 ) .  Partial or complete recanalization was observed in 10 of the 17 patients . Neurological improvement at 24 hours ( > or=4 point reduction in NIHSS score ) was observed in 11 of 17 patients . Comparisons with matched controls suggest potential equivalence for symptomatic ICH ( 0 % vs 12 % ) , asymptomatic ICH ( 18 % vs 15 % ) , and early neurological improvement ( 65 % vs 53 % ) . CONCLUSION The study shows that aggressive mechanical thrombus disruption in large artery occlusion in the setting of acute ischemic stroke is safe with acceptable rates of ICH and promotes angiographic recanalization Background and Purpose — The purpose of this study was to evaluate the safety and efficacy of direct percutaneous transluminal angioplasty ( PTA ) for patients with acute middle cerebral artery ( MCA ) trunk occlusion . Methods — Over the past 9 years , a total of 70 patients with acute MCA trunk occlusion were treated with intra-arterial reperfusion therapy . In the last 5 years , 34 patients were treated with direct PTA  , and subsequent thrombolytic therapy was added if necessary for distal embolization . The other 36 patients , mainly in the first 4 years , were treated with thrombolytic therapy alone and were used as controls .  Pretherapeutic neurological status was evaluated with National Institutes of Health Stroke Scale scores . The modified Rankin Scale ( mRS ) was used to assess clinical outcome at 90 days . Results — There were no significant differences in pretherapeutic National Institutes of Health Stroke Scale score and duration of ischemia between the 2 groups . The rate of partial or complete recanalization in the PTA group was 91.2 % , whereas that in the thrombolysis-alone group was 63.9 % ( P < 0.01 ) . The incidence of large parenchymal hematoma with neurological deterioration in the PTA group was 2.9 % , while that in the thrombolysis-alone group was 19.4 % ( P = 0.03 ) . Although direct PTA did not improve the rate of favorable outcome ( mRS score 0 or 1 ; 41.7 % for the thrombolysis-alone group versus 52.9 % for the PTA group;P = 0.48 ) , outcome in terms of independence ( mRS score 0 , 1 , 2 ) was significantly better in the PTA group ( 73.5 % ) than in the thrombolysis-alone group ( 50.0%;P = 0.04 ) . Conclusions — Although definitive conclusions on the comparative merits of these 2 therapies can not be drawn because of an open trial , direct PTA may be an effective alternative option to intra-arterial thrombolysis for acute MCA trunk occlusion Background and Purpose — The purpose of this clinical evaluation was to assess the safety and effectiveness of the Penumbra System in the revascularization of patients presenting with acute ischemic stroke secondary to intracranial large vessel occlusive disease . Methods — In this prospect i ve , multicenter , single-arm study , 125 patients with neurological deficits as defined by a National Institutes of Health Stroke Scale score ≥8 , presented within 8 hours of symptom onset , and an angiographic occlusion ( Thrombolysis In Myocardial Infa rct ion [ TIMI ] Grade 0 or 1 ) of a treatable large intracranial vessel were enrolled . Patients who presented within 3 hours from symptom onset had to be ineligible or refractory to recombinant tissue plasminogen activator therapy .  All patients were followed clinical ly for 90 days postprocedure . Results — A total of 125 target vessels in 125 patients were treated by the Penumbra System . Postprocedure , 81.6 % of the treated vessels were successfully revascularized to TIMI 2 to 3 . There were 18 procedural events reported in 16 patients ( 12.8 % ) , 3 patients ( 2.4 
    Output:
    
MET is associated with acceptable safety and efficacy in stroke patients , and it may be a therapeutic option in those presenting with isolated middle cerebral artery occlusion