What is the recommended treatment for M1 (Middle Cerebral Artery) occlusion thrombectomy?

Mechanical Thrombectomy for M1 Occlusion

Mechanical thrombectomy with a stent retriever is strongly recommended as first-line treatment for patients with M1 (middle cerebral artery) occlusion who meet eligibility criteria, with treatment initiated within 6 hours of symptom onset. 1

Primary Eligibility Criteria

• Patients should receive mechanical thrombectomy with a stent retriever if they meet all of the following criteria:
  • Prestroke modified Rankin Scale (mRS) score of 0 to 1 1, 2
  • Causative occlusion of the internal carotid artery or MCA segment 1 (M1) 1, 2
  • Age ≥18 years 1, 2
  • NIHSS score of ≥6 1, 2
  • ASPECTS of ≥6 1, 2
  • Treatment can be initiated (groin puncture) within 6 hours of symptom onset 1, 2

Treatment Protocol

• Do not delay mechanical thrombectomy to observe for clinical response after IV alteplase administration (Class III: Harm recommendation) 1
• The technical goal of thrombectomy should be to achieve reperfusion with a modified Thrombolysis in Cerebral Infarction (mTICI) grade 2b/3 3, 2
• Stent retrievers are the preferred devices for mechanical thrombectomy 1, 2
• Time to treatment is critical - each 1-hour delay to reperfusion is associated with:
  • Less favorable degree of disability (common odds ratio 0.84) 1
  • Reduced functional independence (odds ratio 0.81) 1

Extended Time Window Considerations

• For patients within 6-16 hours of last known normal, mechanical thrombectomy is recommended if they meet DAWN or DEFUSE 3 eligibility criteria 2
• For patients within 16-24 hours of last known normal, mechanical thrombectomy is reasonable if they meet DAWN eligibility criteria 2
• Advanced imaging (CTP or DW-MRI with or without MRI perfusion) is required for patient selection in the extended time window 2

Special Considerations

• Pretreatment with IV alteplase is not required for mechanical thrombectomy eligibility, as demonstrated by the HERMES collaboration analysis (cOR 2.43; 95% CI 1.30-4.55) 1
• Mechanical thrombectomy shows benefit across age groups, including patients ≥80 years old (cOR 3.68; 95% CI 1.95-6.92) 1
• For patients ≥90 years of age, the benefit is less clear due to limited trial data, and comorbidities should be carefully considered 1

M2 Occlusions

• Mechanical thrombectomy may be reasonable for carefully selected patients with M2 occlusions within 6 hours of symptom onset (Class IIb recommendation) 1, 3
• The HERMES meta-analysis showed a positive treatment effect for M2 occlusions, though the adjusted common odds ratio was not statistically significant (1.28; 95% CI: 0.51-3.21) 3
• Reperfusion in patients with M2 occlusions has been associated with excellent functional outcomes (mRS 0-1; OR: 2.2; 95% CI: 1.0-4.7) 3

Implementation Requirements

• Treatment requires an experienced stroke center with immediate access to cerebral angiography and qualified interventionalists 2
• Patients should be transported rapidly to the closest available certified primary stroke center or comprehensive stroke center 2
• An integrated, multidisciplinary approach including stroke physicians, interventional cardiologists, neurologists, radiologists, and anesthesiologists is essential for optimal treatment decisions 1

Clinical Outcomes

• Early thrombectomy can provide excellent outcomes, with case reports demonstrating complete recovery with no infarct when treatment is initiated rapidly 4
• Stent-based thrombectomy has shown high rates of successful recanalization (90-100%) and good functional outcomes (mRS 0-2) in 77% of patients at 90 days 5

Common Pitfalls and Caveats

• Observing for clinical response after IV alteplase before pursuing mechanical thrombectomy should be avoided as it delays treatment and worsens outcomes 1
• IV thrombolysis should not be withheld in eligible patients, even if mechanical thrombectomy is being considered 3, 2
• Strict adherence to DAWN or DEFUSE-3 eligibility criteria is necessary for patient selection in the extended time window 2