What is the recommended physical exam and management for a patient with a right M2 (middle cerebral artery) occlusion?

Physical Examination and Management for Right M2 Occlusion

Mechanical thrombectomy with stent retrievers is recommended for carefully selected patients with right M2 occlusion when treatment can be initiated within 6 hours of symptom onset, despite uncertain benefits compared to proximal occlusions. 1

Physical Examination for Right M2 Occlusion

Neurological Assessment

• NIHSS (National Institutes of Health Stroke Scale) assessment is essential for baseline evaluation and monitoring
• Look for specific deficits associated with right M2 occlusion:
  • Left-sided hemiparesis (face, arm, leg)
  • Left-sided sensory deficits
  • Left visual field defect (homonymous hemianopia)
  • Left-sided neglect
  • Aphasia (if dominant hemisphere affected)
  • Dysarthria

Vital Signs Monitoring

• Blood pressure measurement (arterial line monitoring if available)
• Heart rate and rhythm (to detect atrial fibrillation or other arrhythmias)
• Oxygen saturation
• Temperature

Vascular Assessment

• Check for carotid bruits
• Assess peripheral pulses for symmetry
• Evaluate for signs of peripheral vascular disease

Imaging Assessment

Initial Imaging

• Non-contrast CT brain - to rule out hemorrhage and assess for early ischemic changes
• CT Angiography (CTA) - to confirm M2 occlusion and assess collateral circulation
• CT Perfusion - to evaluate core infarct and penumbra

Advanced Imaging (if time permits)

• MRI with diffusion-weighted imaging - to assess infarct core
• MR Angiography - for detailed vascular anatomy

Management Algorithm

Immediate Management (0-6 hours from symptom onset)

1. IV thrombolysis

   • Administer IV rtPA if within 4.5 hours and no contraindications
   • The availability of endovascular therapy should not preclude IV thrombolysis in eligible patients 1

2. Endovascular Treatment Evaluation

   • Consider mechanical thrombectomy if:
     • Treatment can be initiated within 6 hours of symptom onset
     • Patient has disabling neurological deficits
     • No large established infarct on imaging 1

3. Mechanical Thrombectomy Procedure

   • Use stent retrievers for M2 occlusions
   • Technical success rates (modified TICI 2b-3) of approximately 75-80% can be expected 2, 3
   • Good functional outcomes (mRS ≤2) occur in approximately 58-72% of treated patients 2, 3

Extended Time Window Management (6-24 hours)

1. Advanced Imaging Selection

   • For patients presenting between 6-16 hours: Apply DAWN or DEFUSE-3 criteria
   • For patients presenting between 16-24 hours: Apply DAWN criteria 1
   • Consider perfusion-core mismatch and clinical-imaging mismatch

2. Mechanical Thrombectomy Decision

   • If patient meets DAWN/DEFUSE-3 criteria and has M2 occlusion, mechanical thrombectomy may be considered, though evidence is stronger for proximal occlusions

Post-Procedure Care

1. Neurological Monitoring

   • Intensive care monitoring for at least 24 hours
   • Regular neurological assessments to detect early deterioration 1

2. Blood Pressure Management

   • Maintain normotensive, euvolemic conditions
   • Consider tight blood pressure control with agents that do not act in the central nervous system 1

3. Complication Surveillance

   • Monitor for symptomatic intracranial hemorrhage (occurs in approximately 5-6% of M2 thrombectomy cases) 4, 3
   • Watch for cerebral edema and mass effect

Special Considerations for M2 Occlusions

1. Anatomical Variations

   • Determine if the occluded M2 branch is dominant or non-dominant
   • Dominant M2 occlusions may have clinical presentations similar to M1 occlusions 4

2. Technical Approach

   • Consider both stent retriever and aspiration techniques
   • Aspiration thrombectomy has shown good results with M2 occlusions (79.6% successful reperfusion) 2

3. Risk-Benefit Assessment

   • M2 occlusions have similar safety profiles to M1 occlusions when treated with mechanical thrombectomy
   • Symptomatic hemorrhage rates are comparable between M2 and M1 occlusions (6.6% vs 5.9%) 4

Clinical Pitfalls and Caveats

1. Avoid delays in treatment - "Time is brain" applies to M2 occlusions as well
2. Don't exclude patients based solely on M2 occlusion location - Evidence suggests benefit similar to M1 occlusions 4
3. Consider individual patient factors - Age, comorbidities, and pre-stroke functional status impact outcomes
4. Recognize anatomical variations - What appears as an M2 occlusion may functionally behave like an M1 occlusion if it's a dominant branch 5
5. Be prepared for hemorrhagic transformation - This is a common complication, especially with reperfusion 1

The management of right M2 occlusions requires rapid assessment, appropriate imaging, and timely intervention with either IV thrombolysis, mechanical thrombectomy, or both, depending on the time window and patient characteristics.