What are the outcomes of thrombectomy for Middle Cerebral Artery (MCA) thrombus?

Outcomes of Thrombectomy for MCA Thrombus

Mechanical thrombectomy for MCA occlusion achieves functional independence (mRS 0-2) in approximately 59% of patients, with successful recanalization rates of 81%, though outcomes vary significantly based on occlusion location (M1 vs M2) and baseline stroke severity. 1

Functional Outcomes

Overall Success Rates

• Functional independence (mRS 0-2) at 90 days occurs in 59% of patients with M2 segment occlusions treated with modern thrombectomy devices 1
• Good functional outcome (mRS 0-2) is achieved in approximately 36-41% of patients with M1 occlusions, depending on the specific device and technique used 2
• Successful recanalization (defined as mTICI 2b/3) is the technical goal and is achieved in 81% of M2 occlusions, with comparable rates between stent-retriever and aspiration techniques 1

Impact of Recanalization on Outcomes

• Successful recanalization is strongly associated with favorable outcomes, with an odds ratio of 4.22 for M2 occlusions compared to poor recanalization 1
• In patients with severe baseline strokes (ASPECTS 0-5), achieving successful reperfusion provides an adjusted odds ratio of 5.53 for favorable outcome and 5.58 for functional independence 3
• Recanalization rates are comparable between M1 and M2 occlusions, with no significant difference in technical success 1

Mortality Outcomes

• Overall mortality at 90 days ranges from 16-20% for M2 occlusions 1
• Mortality is higher (33-34%) in patients with M1 occlusions and those treated with earlier-generation devices 2
• In patients with severe strokes (ASPECTS 0-5), successful reperfusion reduces mortality with an adjusted odds ratio of 0.18 3
• Even in patients with ASPECTS 0-4, the mortality-reducing effect of successful reperfusion remains significant (aOR 0.167) 3

Safety and Hemorrhagic Complications

Symptomatic Intracranial Hemorrhage

• Symptomatic intracranial hemorrhage (sICH) occurs in approximately 10% of patients with M2 occlusions 1
• For M1 occlusions, sICH rates range from 6-11% depending on the device and technique used 2
• Successful reperfusion is associated with lower rates of sICH (aOR 0.235) in patients with severe baseline strokes, contrary to concerns about increased hemorrhagic risk 3

Procedural Complications

• Procedural complications occur in 6-13% of patients, including device malfunctions and thromboembolic events 2
• The risk of hemorrhagic complications does not increase with successful recanalization, even in patients with large baseline infarcts 3

Comparative Outcomes: Bridging vs Direct Thrombectomy

• Bridging thrombolysis (IV tPA followed by thrombectomy) achieves better functional outcomes than direct thrombectomy alone, with higher rates of functional independence regardless of IV tPA eligibility 2
• The bridging approach results in higher successful recanalization rates (mTICI 2b-3) compared to direct thrombectomy 2
• Mortality at 90 days is lower with bridging therapy, without increasing the risk of symptomatic intracranial hemorrhage 2

Outcomes by Occlusion Location

M1 Segment Occlusions

• M1 occlusions generally have lower rates of favorable outcomes compared to M2 occlusions 1
• In patients with M1 occlusions and distance to thrombus <16 mm, combined IV-MT achieves significantly better outcomes than IV thrombolysis alone (7-day NIHSS improvement: 10.9 vs 6.7; 90-day mRS: 2 vs 4) 4

M2 Segment Occlusions

• M2 thrombectomy is associated with 59% functional independence, though the evidence level is lower (Class IIb recommendation) 5
• Recanalization rates for M2 occlusions are equivalent to M1 occlusions (OR 1.05), suggesting technical feasibility 1
• The primary recommendation for M2 thrombectomy applies to a 6-hour time window from symptom onset 5

Special Populations

Elderly Patients

• Thrombectomy in octogenarians and nonagenarians is technically feasible with acceptable recanalization rates 2
• Clinical outcomes at 90 days are improved in elderly patients who receive thrombectomy compared to those who do not, though outcomes are worse than in younger patients 2
• Symptomatic intracranial hemorrhage rates may be higher in elderly patients undergoing thrombectomy 2

Patients with Severe Baseline Strokes (ASPECTS 0-5)

• In patients with ASPECTS 0-5, favorable outcome (mRS 0-3) occurs in 40.1% of cases, with mortality of 40.9% 3
• Successful reperfusion remains beneficial in this population without increasing hemorrhagic risk 3

Critical Time Considerations

• The benefit of thrombectomy declines with time, though the decline may be 2.5-fold less than for IV thrombolysis alone in large vessel occlusions 2
• For extended time windows (6-24 hours), strict adherence to DAWN or DEFUSE-3 criteria is essential, particularly for M2 occlusions 5
• IV thrombolysis should not be delayed or withheld while considering thrombectomy, and evaluation of response to IV tPA should not delay catheter angiography 5

Common Pitfalls to Avoid

• Failing to achieve adequate recanalization (mTICI 2b/3) significantly worsens outcomes, as the association between successful reperfusion and favorable outcomes is strong across all patient subgroups 1, 3
• Withholding thrombectomy from patients with large baseline infarcts (ASPECTS 0-5) may deny them the mortality-reducing benefits of successful reperfusion 3
• Bypassing IV thrombolysis in eligible patients reduces the likelihood of successful recanalization and favorable outcomes 2
• In patients with M1 occlusions and short distance to thrombus (<16 mm), relying on IV thrombolysis alone results in significantly worse outcomes than combined therapy 4