What is the time window for administering IV thrombolysis with alteplase (tissue plasminogen activator) in an adult patient with acute cerebellar stroke?

Time Window for IV Thrombolysis in Cerebellar Stroke

IV alteplase should be administered to patients with acute cerebellar stroke using the same time windows as anterior circulation strokes: within 4.5 hours of symptom onset or last known well, with the standard 0-4.5 hour window applying equally to all ischemic stroke locations including the cerebellum. 1, 2

Standard Time Windows Apply to All Ischemic Strokes

The American Heart Association guidelines make no distinction between anterior and posterior circulation strokes (including cerebellar strokes) for IV thrombolysis time windows 1. The evidence-based approach is:

0-3 Hour Window (Class I, Level A)

• IV alteplase (0.9 mg/kg, maximum 90 mg) is strongly recommended for cerebellar stroke patients who can be treated within 3 hours of symptom onset 1, 2
• This represents the strongest evidence base, supported by the NINDS trials which included all ischemic stroke subtypes 1
• 10% of dose given as IV bolus over 1 minute, remaining 90% infused over 60 minutes 1, 2

3-4.5 Hour Window (Class I, Level B-R)

• IV alteplase is also recommended for cerebellar stroke patients presenting between 3-4.5 hours from symptom onset 1, 2
• This is based on ECASS-III data, which demonstrated improved clinical outcomes despite higher symptomatic intracranial hemorrhage rates (2.4% vs 0.2%) 1, 3
• The benefit-to-risk ratio remains favorable in this extended window 3

Critical Imaging Requirements Before Treatment

Non-contrast CT or MRI must exclude intracranial hemorrhage before administering alteplase 4, 2. For cerebellar strokes specifically:

• Posterior circulation Alberta Stroke Program Early CT Score (pc-ASPECTS) should be ≥8, indicating minimal early ischemic changes 4
• Extensive bilateral and/or brainstem ischemic changes are absolute contraindications 4
• The presence of >1/3 territory involvement with early ischemic changes should preclude treatment 2

Blood Pressure Management is Critical

Blood pressure must be controlled to <185/110 mmHg before initiating alteplase and maintained below this threshold during and after infusion 1, 2. Persistently elevated blood pressure despite treatment is an absolute contraindication 2.

Extended Window Considerations (4.5-9 Hours)

While not standard practice, the World Stroke Organization guidelines suggest considering IV alteplase for cerebellar strokes presenting 4.5-9 hours after onset if CT or MRI demonstrates core/perfusion mismatch and mechanical thrombectomy is not indicated 5. However, this requires:

• Advanced perfusion imaging demonstrating salvageable tissue 5
• Confirmation that mechanical thrombectomy is not planned 5
• This approach is more established for basilar artery occlusion than isolated cerebellar infarction 4

Common Pitfalls to Avoid

Do not withhold IV alteplase from cerebellar stroke patients based on:

• Severe symptoms or high NIHSS scores - severity alone is not a contraindication 1, 2
• Age >80 years - octogenarians benefit from thrombolysis despite ECASS-III exclusion criteria 1
• Mild symptoms - cerebellar strokes can appear deceptively mild but cause devastating disability from brainstem compression 1, 2

Critical contraindications that must be respected:

• Active internal bleeding or recent major surgery within 3 months 2
• Platelet count <100,000/mm³ 2
• INR >1.7 or recent DOAC use with elevated laboratory tests 1, 2
• Blood glucose <50 mg/dL 2

Relationship to Endovascular Therapy

For cerebellar strokes caused by basilar artery occlusion, combined IV thrombolysis and endovascular therapy is preferred over endovascular therapy alone when IV alteplase is not contraindicated 4. The rationale is:

• IV thrombolysis can be initiated immediately without delays from invasive procedures 4
• Observational data show 47-50% of basilar artery occlusion patients achieve favorable outcomes (mRS 0-3) with IV alteplase alone 4
• This is particularly important for centers lacking immediate endovascular capabilities 4

Door-to-Needle Time Targets

Target door-to-needle time is <60 minutes in 90% of patients, with a median goal of 30 minutes 2. Every minute of delay reduces the probability of good outcome, making rapid treatment initiation essential even for cerebellar strokes 1.