What is the time window for intravenous (IV) thrombolysis using alteplase (tissue plasminogen activator) in a patient with acute basilar stroke?

Time Window for IV Thrombolysis in Basilar Stroke

For adults with acute basilar artery occlusion presenting within 4.5 hours from last known well, without contraindications and without extensive posterior circulation ischemic changes, IV alteplase should be administered. 1

Evidence-Based Time Window

The 2024 European Stroke Organisation (ESO) and European Society for Minimally Invasive Neurological Therapy (ESMINT) guidelines provide the most current guidance on this specific question. While there is insufficient high-quality evidence to make a formal evidence-based recommendation for basilar artery occlusion (BAO), the expert consensus is clear:

• Within 4.5 hours: All 10/10 guideline panel members recommend IV thrombolysis for BAO patients presenting within 4.5 hours from last known well, provided there are no contraindications and no extensive ischemic changes in the posterior circulation (pc-ASPECTS ≥8). 1

• Beyond 4.5 hours up to 24 hours: There are insufficient data to make an evidence-based recommendation, though observational data suggest potential benefit in highly selected patients. 1

Critical Selection Criteria

Imaging requirements before administering alteplase in basilar stroke:

• Non-contrast CT or MRI must exclude intracranial hemorrhage 1
• Posterior circulation Alberta Stroke Program Early CT Score (pc-ASPECTS) should be ≥8 (meaning minimal early ischemic changes) 1
• Extensive bilateral and/or brainstem ischemic changes are contraindications 1

Standard alteplase eligibility criteria apply, including blood pressure <185/110 mmHg, no recent surgery, normal coagulation parameters, and appropriate platelet count. 2, 3

Dosing and Administration

• Dose: 0.9 mg/kg body weight (maximum 90 mg total) 2, 3
• Administration: 10% as IV bolus over 1 minute, remaining 90% infused over 60 minutes 2, 3
• Time target: Door-to-needle time should be <60 minutes, with median target of 30 minutes 2, 3

Relationship to Endovascular Therapy

Combined IVT and EVT is preferred over EVT alone when IVT is not contraindicated in basilar artery occlusion. 1

• Do not delay IV alteplase to arrange endovascular therapy 1
• IV thrombolysis should be first-line therapy for posterior circulation stroke, as it prevents delays from invasive procedures and is appropriate for centers lacking endovascular expertise 1
• Observational data show that IV alteplase alone in BAO patients achieved favorable outcomes (mRS 0-3) in 47-50% of cases, comparable to EVT outcomes in recent trials 1

Supporting Evidence and Rationale

The catastrophic prognosis of untreated basilar artery occlusion has made randomized trials comparing IVT to placebo ethically impossible for over two decades. 1 Consequently, many centers have considered IVT standard treatment for this condition despite the lack of RCT evidence specific to BAO. 1

Key observational findings:

• In angiography-verified BAO patients (median NIHSS 17) with pc-ASPECTS ≥8, up to 50% achieved good outcomes (mRS 0-3) at 3 months regardless of time window (up to 48 hours). 1
• Symptomatic intracranial hemorrhage rates ranged from 7-11%, consistent with anterior circulation stroke data. 1
• A meta-analysis comparing IV versus intra-arterial thrombolysis found roughly equal survival and outcomes (22% vs 24% good outcomes). 1

Common Pitfalls to Avoid

Do not withhold IV alteplase from basilar stroke patients due to:

• Severe symptoms (high NIHSS score) - these patients have catastrophic prognosis without treatment and may still benefit 1
• Age >80 years - this is not a contraindication within the 4.5-hour window 1, 3
• Preference for endovascular therapy - IV thrombolysis should be administered first if eligible, as it avoids procedural delays 1

Critical contraindication: Extensive bilateral and/or brainstem ischemic changes on baseline imaging remain an absolute contraindication. 1

Practical Algorithm

1. Confirm basilar artery occlusion clinically and with imaging (CT angiography or MR angiography)
2. Determine time from last known well - if <4.5 hours, proceed with evaluation
3. Obtain non-contrast CT or MRI to exclude hemorrhage and assess pc-ASPECTS
4. If pc-ASPECTS ≥8 and no contraindications exist, administer IV alteplase 0.9 mg/kg
5. Simultaneously arrange endovascular therapy if available, but do not delay IV thrombolysis 1

The 4.5-hour window represents the evidence-supported timeframe for basilar stroke thrombolysis, mirroring anterior circulation stroke guidelines while acknowledging the unique catastrophic natural history of untreated basilar occlusion. 1