***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: Eighteen patients underwent stenting for symptomatic basilar artery stenosis . There were three major periprocedural complications ( 16.7 % ) without fatality . At a mean 26.7 ± 12.1-month follow-up , 15 patients ( 83.3 % ) had an excellent long-term outcome . Only one patient ( 5.6 % ) had moderate disability from recurrent stroke , and two patients died of medical illness at 30 and 36 months after stenting . In this uncontrolled study , stenting appeared to be effective in reducing stroke risk and death and worthy of further scrupulous trial BACKGROUND AND PURPOSE There are limited data on the prognosis of patients with angiographically proved symptomatic stenosis of the intracranial vertebral artery or basilar artery . METHODS We studied 68 patients with 50 % to 99 % stenosis of one of the following arteries : intracranial vertebral ( n = 31 ) , basilar ( n = 28 ) , posterior cerebral ( PCA ) ( n = 6 ) , or posterior inferior cerebellar ( PICA ) ( n = 3 ) . All patients had previous transient ischemic attack or stroke in the territory of the stenotic artery and were treated with warfarin ( n = 42 ) or aspirin ( n = 26 ) . Follow-up was by chart review and personal or telephone interview . RESULTS During a median follow-up of 13.8 months , 15 patients ( 22 % ) had an ischemic stroke ( 4 fatal ) , 3 patients ( 4.5 % ) had a fatal myocardial infa rct ion ( MI ) or sudden death , and 6 patients ( 9 % ) had a nonfatal MI . Stroke rates in any vascular territory ( per 100 patient-years of follow-up ) were 15.0 in patients with basilar artery stenosis , 13.7 in patients with vertebral artery stenosis , and 6.0 in patients with PCA or PICA stenosis . Stroke rates in the same territory as the stenotic artery ( per 100 patient-years of follow-up ) were 10.7 in patients with basilar artery stenosis , 7.8 in patients with vertebral artery stenosis , and 6.0 in patients with PCA or PICA stenosis . CONCLUSIONS Patients with symptomatic intracranial vertebral artery or basilar stenosis are at high risk of stroke , MI , or sudden death . Further studies are needed to clarify optimal therapy for these patients Background — Antithrombotic therapy for intracranial arterial stenosis was recently evaluated in the Warfarin versus Aspirin for Symptomatic Intracranial Disease ( WASID ) trial . A prespecified aim of WASID was to identify patients at highest risk for stroke in the territory of the stenotic artery who would be the target group for a subsequent trial comparing intracranial stenting with medical therapy . Methods and Results — WASID was a r and omized , double-blinded , multicenter trial involving 569 patients with transient ischemic attack or ischemic stroke due to 50 % to 99 % stenosis of a major intracranial artery . Median time from qualifying event to r and omization was 17 days , and mean follow-up was 1.8 years . Multivariable Cox proportional hazards models were used to identify factors associated with subsequent ischemic stroke in the territory of the stenotic artery . Subsequent ischemic stroke occurred in 106 patients ( 19.0 % ) ; 77 ( 73 % ) of these strokes were in the territory of the stenotic artery . Risk of stroke in the territory of the stenotic artery was highest with severe stenosis ≥70 % ( hazard ratio 2.03 ; 95 % confidence interval 1.29 to 3.22 ; P=0.0025 ) and in patients enrolled early ( ≤17 days ) after the qualifying event ( hazard ratio 1.69 ; 95 % confidence interval 1.06 to 2.72 ; P=0.028 ) . Women were also at increased risk , although this was of borderline significance ( hazard ratio 1.59 ; 95 % confidence interval 1.00 to 2.55 ; P=0.051 ) . Location of stenosis , type of qualifying event , and prior use of antithrombotic medications were not associated with increased risk . Conclusions — Among patients with symptomatic intracranial stenosis , the risk of subsequent stroke in the territory of the stenotic artery is greatest with stenosis ≥70 % , after recent symptoms , and in women Background and aim Posterior circulation stenosis may be a risk factor associated with stroke after intracranial stenting as compared with anterior circulation stenosis . Our aim was to test our hypothesis that there was no difference in clinical outcome poststenting between patients with severe stenosis of the basilar artery ( BA ) and intracranial vertebral artery ( VA ) . Methods Using the Cox proportional hazards regression model adjusted for prespecified factors ( qualifying event , and timing of stenting after the qualifying event ) , we compared primary endpoint ( ischemic stroke in the vertebrobasilar territory , including any stroke or death within 30 days of stenting ) between patients with severe symptomatic atherosclerotic BA and VA stenosis who underwent elective stenting in our prospect i ve data base . Analysis was by intention-to-treat principle . Results Primary endpoint event occurred in 13 ( 18.8 % ) of 69 patients with BA stenosis during a mean 23.4 months ( 9 within 30 days and 4 afterward ) and 3 ( 4.3 % ) of 70 patients with VA stenosis during a mean 26.4 months ( 2 within 30 days and 1 afterward ) . Patients with BA stenosis had a significantly higher risk of the primary endpoint ( adjusted HR=4.87 , 95 % CI 1.37 to 17.29 ; p=0.014 ) or any stroke or death within 30 days of stenting ( adjusted HR=5.13 , 95 % CI 1.10 to 23.96 ; p=0.038 ) than those with VA stenosis . Conclusion A significantly higher stroke risk poststenting exists in patients with severe BA stenosis than those with VA stenosis . The discrepancy in clinical outcome after stenting between patients with BA and VA stenosis should be considered in clinical practice and stenting trials Background : Symptomatic intracranial atherothrombotic stenoses ( ICAS ) are associated with high rates of cerebrovascular ischemic events . Objective : To conduct a prospect i ve multicenter study to evaluate the natural history of ICAS and , in those patients refractory to medical treatment , the outcomes associated with intracranial angioplasty . Methods : Patients aged 18 to 80 were enrolled with symptoms attributed to a single ICAS of ≥50 % .  Optimal medical therapy of vascular risk factors and preventive antithrombotic therapy were at the discretion of the local investigator . Patients were eligible for intracranial angioplasty after experiencing recurrent stroke despite medical therapy . Neurologic and ultrasonographic examinations were performed at study inclusion , 3 months after enrollment , and every 6 months of follow-up thereafter , for 36 months . Results : One hundred two patients were included , with a mean age of 63.3 ± 10.4 years . Intracranial artery stenoses involved the vertebral artery in 22.5 % , the basilar artery in 25.5 % , the middle cerebral artery in 26.5 % , and the internal carotid artery in 25.5 % . In 27.4 % of the patients , the stenoses had clinical hemodynamic characteristics . During a mean follow-up of 23.4 months , 38.2 % of the patients had a cerebrovascular event : ischemic stroke in 13.7 % and TIA in 24.5 % . Among patients with a hemodynamically significant stenosis , 60.7 % had a recurrent stroke or TIA in the territory of the stenotic artery ; this association was significant in univariate analysis . Twenty-eight patients underwent an endovascular procedure  with a neurologic periprocedural complication rate of 14.2 % . The overall vascular death rate was 8.8 % . Conclusions : Despite medical treatment , the 2-year recurrence rate of ischemic events in the territory of the stenotic artery was 38.2 % . Cardiovascular events occurred in 18.6 % of patients . Clinical ly significant hemodynamic stenoses were associated with stroke recurrence and may help identify a high risk subset of patients Background and Purpose — 20 % of ischemic stroke is in the posterior circulation , but there is little prospect i ve data on early recurrent stroke risk and whether vertebrobasilar stenosis predicts a high recurrence risk . This natural history data are important as it is technically possible to stent such lesions . Contrast enhanced MRA ( CE-MRA ) and CT angiography ( CTA ) now allow noninvasive identification of vertebrobasilar stenosis . Methods — 216 consecutive patients presenting with posterior circulation TIA or stroke were recruited and prospect ively followed for 90 days . 8 patients with vertebral dissection were excluded .  CE-MRA or CTA at presentation and 90-day follow-up was available in 182 . Any posterior circulation TIA/stroke in the month before the presenting episode was recorded . Results — Taking the first event ( including TIA/stroke in the previous month ) as the index case recurrent stroke risk in patients with stenosis was 30.5 % versus 8.9 % in those without ; RR 3.4 ( 95 % CI 1.7 to 7.0 ) , P<0.001 ) . Taking the presenting episode as the index case the risk was 13.8 % versus 4.1 % ; RR 3.4 ( 95 % CI 1.1 to 10.5 ) P=0.0274 . The probability of recurrence was highest soon after the initial event . Conclusions — The presence of vertebro-basilar stenosis identifies a group of patients with posterior circulation stroke who have a high early recurrent stroke risk . Early intervention might reduce recurrent stroke risk . Vertebral stenosis can now be treated by stenting , but determining whether this reduces the early stoke risk requires r and omized controlled trials Objective : To determine the prognosis of patients with symptomatic intracranial atherosclerosis who fail antithrombotic therapy .  Background : The outcome of patients with symptomatic intracranial atherosclerosis who fail antithrombotic therapy  is unknown . These patients may represent the target group for investigation of more aggressive therapies such as intracranial angioplasty . Methods : The authors performed a chart review and telephone interview of patients with symptomatic intracranial atherosclerosis identified in the Stanford Stroke Center clinical data base . A Cox regression model was created to identify factors predictive of failure of antithrombotic therapy . The authors generated Kaplan – Meier survival curves to determine the timing of recurrent TIA , stroke , or death after failure of antithrombotic therapy . Results : Fifty-two patients had symptomatic intracranial atherosclerosis and fulfilled entry criteria . Twenty-nine of the 52 patients ( 55.8 % ) had cerebral ischemic events while receiving an antithrombotic agent ( antiplatelet agents [ 55 % ] , warfarin [ 31 % ] , or heparin [ 14 % ] ) . In a Cox regression model , older age was an independent predictor of failure of antithrombotic therapy , and warfarin use was associated with a decrease in risk . Recurrent TIA ( n = 7 ) , nonfatal/fatal stroke ( n = 6/1 ) , or death ( n = 1 ) occurred in 15 of 29 ( 51.7 % ) of the patients who failed antithrombotic therapy . The median time to recurrent TIA , stroke , or death was 36 days ( 95 % CI 13 to 59 ) . Conclusions : Patients with symptomatic intracranial atherosclerosis who fail antithrombotic therapy  have extremely high rates of recurrent TIA/stroke or death . Recurrent ischemic events typically occur within a few months after failure of st and ard medical therapy . The high recurrence risk observed warrants testing of alternative treatment strategies such as intracranial angioplasty We conducted a retrospective , multicenter study to compare the efficacy of warfarin with aspirin for the prevention of major vascular events ( ischemic stroke , myocardial infa rct ion , or sudden death ) in patients with symptomatic stenosis of a major intracranial artery . Patients with 50 to 99 % stenosis of an intracranial artery ( carotid ; anterior , middle , or posterior cerebral ; vertebral ; or basilar ) were identified by review ing the results of consecutive angiograms performed at participating centers between 1985 and 1991 . Only patients with TIA or stroke in the territory of the stenotic artery qualified for inclusion in the study . Patients were prescribed warfarin or aspirin according to local physician preference and were followed by chart review and personal or telephone interview . Seven centers enrolled 151 patients ; 88 were treated with warfarin and 63 were treated with aspirin .  Median follow-up was 14.7 months ( warfarin group ) and 19.3 months ( aspirin group ) . Vascular risk factors and mean percent stenosis of the symptomatic artery were similar 
    Output:
    
A small preventive effect of endovascular therapy may exist , particularly if the 30 day postprocedural risk is reduced