What criteria do patients need to meet to most likely benefit from mechanical thrombectomy, as shown in randomized trials, such as evidence of salvageable brain tissue on advanced imaging, Modified Rankin Scale (MRS) score, National Institute of Health (NIH) Stroke Scale score, or presence of a large anterior circulation vessel occlusion?

Mechanical Thrombectomy Patient Selection Criteria

The correct answer is A: evidence of salvageable brain tissue on advanced imaging. Randomized controlled trials, particularly DAWN and DEFUSE-3, have definitively demonstrated that patients with salvageable brain tissue identified through perfusion imaging (clinical-imaging mismatch or perfusion-core mismatch) achieve superior functional outcomes with mechanical thrombectomy. 1

Key Trial Evidence Supporting Salvageable Tissue Selection

The landmark trials establishing thrombectomy benefit specifically required demonstration of salvageable brain tissue:

• The DAWN trial used clinical-imaging mismatch (combining NIHSS with CTP or DW-MRI findings) and demonstrated 49% versus 13% achieved good functional outcome (mRS 0-2) with thrombectomy versus control (adjusted difference 33%, 95% CI 21-44). 1

• The DEFUSE-3 trial used perfusion-core mismatch criteria and showed 44.6% versus 16.7% achieved good functional outcome with thrombectomy (RR 2.67,95% CI 1.60-4.48, P<0.0001). 1

• The AHA/ASA guidelines explicitly state that DAWN or DEFUSE-3 eligibility criteria should be strictly adhered to in clinical practice, and these trials are the only RCTs showing benefit beyond 6 hours. 1

Why the Other Options Are Incorrect

Option B (Modified Rankin Scale >2) is wrong:

• Patients most likely to benefit have pre-stroke mRS 0-1, not >2. 2
• Good baseline functional status is a selection criterion FOR thrombectomy, not against it. 2

Option C (NIHSS <6) is wrong:

• Patients require NIHSS ≥6 to benefit from thrombectomy. 3, 2
• The BASICS registry demonstrated universally poor outcomes when recanalization was achieved in patients with NIHSS ≤6. 4
• Low NIHSS indicates insufficient stroke severity to justify the procedural risks. 4

Option D (no evidence of large vessel occlusion) is wrong:

• This is the opposite of what's needed—patients must have documented large vessel occlusion (LVO) of the anterior circulation. 3, 2
• Thrombectomy specifically targets removal of thrombi from large, proximal intracranial arteries. 5

Time-Based Imaging Requirements

The imaging requirements differ based on time from symptom onset:

• Within 0-6 hours: Noncontrast CT plus CTA is sufficient if ASPECTS ≥6, NIHSS ≥6, and LVO is confirmed—advanced perfusion imaging is not mandatory in this early window. 3

• Beyond 6-24 hours: CTP or DW-MRI with perfusion imaging is required to demonstrate salvageable tissue (sizable mismatch between ischemic core and hypoperfusion area). 1, 3

Complete Selection Criteria for Thrombectomy

Patients most likely to benefit meet ALL of the following:

• Age ≥18 years 2
• Pre-stroke mRS 0-1 (functionally independent) 2
• NIHSS ≥6 (sufficient stroke severity) 3, 2
• ASPECTS ≥6 (limited irreversible injury) 3, 2
• Documented large vessel occlusion (ICA or M1 segment) 2
• Treatment initiated within 6 hours, OR if 6-24 hours, must have salvageable tissue on perfusion imaging 1, 3

Common Pitfalls to Avoid

Do not delay thrombectomy for unnecessary testing:

• Only blood glucose measurement must precede treatment—other labs (INR, aPTT, platelets) should not delay reperfusion therapy. 3
• Multimodal imaging should not delay IV alteplase administration. 1

Do not perform thrombectomy in patients with extensive established infarction:

• ASPECTS 0 indicates extensive irreversible damage and is a contraindication. 2
• Absence of perfusion mismatch indicates no salvageable tissue. 2