What are the ESC/NICE guidelines for thrombolysis in posterior circulation stroke?

Thrombolysis in Posterior Circulation Stroke: ESC/NICE Guidelines

Direct Recommendation

Intravenous alteplase (0.9 mg/kg; maximum 90 mg) should be administered to patients with posterior circulation stroke presenting within 4.5 hours of symptom onset, and expert consensus supports its use up to 24 hours in basilar artery occlusion when no contraindications exist and there are no extensive ischemic changes (pc-ASPECTS ≥8). 1, 2

Evidence-Based Treatment Algorithm

Within 4.5 Hours of Symptom Onset

• Administer IV alteplase immediately (0.9 mg/kg; maximum 90 mg, with 10% as bolus and remainder over 60 minutes) to all eligible patients with posterior circulation stroke 2, 3
• Posterior circulation stroke accounts for approximately 20% of all ischemic strokes but was largely excluded from early randomized trials 1, 2
• Do not delay IV alteplase while arranging endovascular therapy—the intravenous approach prevents unavoidable delays and is the best option in centers lacking endovascular expertise 1
• Recent meta-analysis demonstrates 63% favorable functional outcome (mRS 0-2) at 90 days with IVT in posterior circulation stroke 3

Extended Time Window (4.5-24 Hours)

• For basilar artery occlusion specifically, the 2024 ESO/ESMINT guidelines provide expert consensus (10/10 voting members) suggesting IVT rather than no IVT when presenting within 4.5 hours without extensive ischemic changes 1
• Groundbreaking 2025 EXPECTS trial demonstrated that alteplase administered 4.5-24 hours after posterior circulation stroke onset resulted in significantly higher functional independence (89.6% vs 72.6%; adjusted RR 1.16,95% CI 1.03-1.30; P=0.01) 4
• This extended window applies to patients without extensive early hypodensity on CT and with no planned thrombectomy 4

Safety Profile: Posterior vs Anterior Circulation

Posterior circulation stroke has a significantly lower hemorrhage risk compared to anterior circulation stroke:

• Symptomatic intracranial hemorrhage occurs in only 3-5% of posterior circulation patients versus 7-8% in anterior circulation 5, 6
• Parenchymal hematoma risk is 5.2 times higher in anterior circulation stroke (P=0.007) 6
• Overall intracranial hemorrhage rate: 8.1% in posterior vs 20.4% in anterior circulation (OR 0.26,95% CI 0.12-0.54) 5
• The EXPECTS trial showed only 1.7% symptomatic ICH rate with alteplase in the extended window 4

Efficacy Outcomes

Posterior circulation stroke responds favorably to thrombolysis:

• 59-64% achieve functional independence (mRS 0-2) at 90 days 3, 6
• Mortality at 90 days ranges from 15-19% 3, 5, 6
• Standard time window (<4.5 hours) shows superior outcomes: 77% favorable outcomes versus 38% in extended window (RR 1.93,95% CI 1.66-2.24) 3
• Posterior circulation patients have higher rates of excellent recovery (55.7% vs 41.6%; OR 2.27) and functional independence (63.9% vs 53.0%; OR 2.33) compared to anterior circulation 5

Basilar Artery Occlusion: Special Considerations

Basilar artery occlusion represents the most devastating posterior circulation stroke:

• Single-arm observational data show up to 50% achieve mRS 0-3 at 3 months when treated with IVT and presenting with pc-ASPECTS ≥8, regardless of time window up to 48 hours 1
• Analysis of 245 patients treated with IVT alone showed 47% favorable outcome (mRS 0-3), identical to EVT arms of recent RCTs 1
• IV alteplase is equally effective as intra-arterial approaches: meta-analysis comparing IV (76 patients) versus intra-arterial (344 patients) thrombolysis found 22% vs 24% good outcomes respectively 1
• There is no good reason why invasive endovascular procedures should be preferred above intravenous thrombolysis for posterior circulation stroke 1

Critical Imaging Criteria

Patient selection based on imaging is essential:

• Non-contrast CT should exclude hemorrhage and assess for extensive early ischemic changes 2
• Posterior circulation ASPECTS (pc-ASPECTS) ≥8 is the key threshold for treatment eligibility 1, 2
• CT angiography or MR angiography should identify large vessel occlusions 2
• MRI with diffusion-weighted imaging is preferred for posterior fossa lesions due to CT beam hardening artifacts 2

Integration with Endovascular Therapy

When both IVT and EVT are indicated:

• For basilar artery occlusion with NIHSS ≥10, EVT plus best medical treatment is suggested over best medical treatment alone 2
• Administer IV alteplase first, then proceed to EVT without delay—do not wait for clinical response to IVT 1, 7
• Successful recanalization is a strong predictor of survival in basilar artery occlusion 2
• Mechanical thrombectomy using stent retrievers or large bore aspiration catheters achieves up to 92% recanalization rates 2

Common Pitfalls to Avoid

• Do not exclude patients based solely on "posterior circulation" designation—these patients have lower hemorrhage risk and excellent outcomes 5, 6
• Do not withhold IVT in basilar artery occlusion while arranging EVT—IV therapy should begin immediately 1
• Do not assume NIHSS accurately reflects severity—the scale underestimates posterior circulation stroke severity as it focuses on limb/speech rather than cranial nerve deficits 2
• Do not restrict treatment to 4.5-hour window for basilar occlusion—expert consensus and recent RCT data support extended windows up to 24 hours 1, 4

Blood Pressure Management

• Maintain systolic BP 121-200 mmHg and diastolic 81-110 mmHg in first 24 hours unless exceeding 220/120 mmHg 2
• Target ≤180/105 mmHg during and for 24 hours after mechanical thrombectomy 8

Guideline Evolution

The 2007 AHA/ASA guidelines provided Class I recommendation for intra-arterial thrombolysis in MCA occlusion but did not specifically address posterior circulation 1. The 2015 AHA/ASA update focused on anterior circulation EVT trials, noting only 8% had posterior circulation strokes 1. The 2024 ESO/ESMINT guidelines represent the first comprehensive, evidence-based approach specifically for basilar artery occlusion 1, and the 2025 EXPECTS trial provides the strongest randomized evidence for extended window treatment in posterior circulation stroke 4.