What is the maximum duration from symptom onset for mechanical thrombectomy (mechanical removal of a blood clot) in the brain?

Maximum Duration for Mechanical Thrombectomy in Acute Stroke

Mechanical thrombectomy for acute ischemic stroke can be performed up to 24 hours from symptom onset in selected patients, with case-by-case consideration possible beyond 24 hours in specific situations. 1, 2

Time Windows for Thrombectomy

Anterior Circulation Strokes

• 0-6 hours: Strong recommendation for thrombectomy regardless of NIHSS (stronger for NIHSS ≥6) 2
• 6-16 hours: Reasonable with DEFUSE 3 criteria (perfusion-core mismatch) 2
• 16-24 hours: Reasonable with DAWN criteria (clinical-imaging mismatch) 2

Posterior Circulation (Basilar Artery Occlusion)

• 0-12 hours: Strongly indicated (Class I, Level B-R) 1
• 12-24 hours: Reasonable (Class IIa, Level B-R) 1
• Beyond 24 hours: May be considered case-by-case (Class IIb, Level C-EO) 1

Patient Selection Criteria

For thrombectomy consideration in extended time windows, patients should meet:

• NIHSS score ≥6
• PC-ASPECTS ≥6 (for posterior circulation)
• ASPECTS ≥6 (for anterior circulation)
• Age 18-89 years (though age alone should not exclude patients) 1, 2

Evidence for Extended Time Windows

The 2024 guidelines from the Journal of Neurointerventional Surgery specifically address basilar artery occlusion (BAO) treatment beyond standard windows. While thrombectomy has proven superior to medical therapy within 24 hours, treatment beyond this timeframe shows:

• Technical feasibility with 50% successful recanalization rates in small studies 1
• Poorer outcomes compared to earlier treatment windows 3
• Comparable safety profile with similar hemorrhage rates to standard window thrombectomy 3, 4

Special Considerations

• Basilar artery occlusions: Often present with non-specific symptoms leading to delayed diagnosis, potentially justifying extended window consideration 1
• Infarct growth velocity: Late-presenting patients often have slower infarct growth (median 0.6 vs 5.1 mL/h), potentially explaining why some patients remain treatable beyond standard windows 5
• M2 occlusions: Some evidence suggests similar outcomes for thrombectomy before and after 6 hours 6

Cautions and Limitations

• Functional outcomes are generally worse when treatment is performed beyond 24 hours, with lower rates of independence (18.8% vs 34.9%) and higher mortality 3
• Patients with NIHSS ≤6 and posterior circulation occlusions have shown universally poor outcomes with late recanalization 1
• Current guidelines do not generally recommend treatment beyond 24 hours from symptom onset 2

Decision-Making Algorithm

1. Determine time from symptom onset/last known well
2. Assess vessel occlusion location (anterior vs posterior circulation)
3. Evaluate clinical severity (NIHSS)
4. Assess early ischemic changes (ASPECTS/PC-ASPECTS)
5. For patients beyond 6 hours, obtain advanced imaging (CT perfusion/MRI)
6. Apply appropriate criteria based on time window:
   • 0-6 hours: Standard criteria
   • 6-24 hours: DAWN/DEFUSE 3 criteria

   • 24 hours: Consider only in select cases with favorable imaging and clinical features

The strongest evidence supports thrombectomy within 24 hours, with treatment beyond this timeframe remaining investigational but potentially reasonable in carefully selected cases.