What is the management of left Middle Meningeal Artery (MMA) embolization?

Middle Meningeal Artery Embolization for Chronic Subdural Hematoma

Middle meningeal artery (MMA) embolization is a minimally invasive endovascular procedure that occludes the MMA to treat chronic subdural hematomas (cSDH), performed via transarterial catheterization with embolic agents, and can be used as primary treatment, adjunct to surgery, or for recurrent hematomas. 1

Indications and Patient Selection

MMA embolization should be considered for:

• New (untreated) chronic subdural hematomas as primary therapy in patients preferring non-surgical management 2, 3
• Recurrent cSDH after failed surgical evacuation 3
• Prophylactic treatment immediately following surgical evacuation to reduce recurrence risk 3
• High-risk surgical patients with significant medical comorbidities who may not tolerate craniotomy 1

The procedure has demonstrated a 91% long-term success rate for avoiding surgical intervention when used as primary or recurrent treatment 3. When used as adjunct therapy combined with surgical evacuation, it reduces treatment failure (OR 0.43), reoperation rates (OR 0.45), and 30-day readmissions (OR 0.50) compared to surgery alone 4.

Procedural Technique

Access and Approach

• Femoral artery access is standard, though transradial access is a viable alternative that allows same-day discharge 1, 2
• Place arterial sheath with direct arterial pressure transduction throughout the procedure 1
• Use 6 French guide catheter for support into the external carotid artery 2

Anesthesia and Monitoring

• Perform under general anesthesia or deep intravenous sedation with continuous neurological monitoring 1
• Mandatory monitoring includes:
  • Direct arterial pressure transduction via femoral sheath 1
  • Pulse oximetry on both the treatment side and the foot receiving the femoral catheter to detect thromboembolic complications 1
  • Continuous neurological and hemodynamic assessment during and for at least 24 hours post-procedure 1

Embolization Strategy

The location and number of branches embolized does not significantly affect outcomes 5. This finding simplifies technical planning:

• Embolization of proximal trunk only, distal branches only, or combined yields similar rescue surgery rates (7.4%, 13.0%, and 6.8% respectively) and similar hematoma volume reduction ≥50% (74.1%, 80.0%, and 77.5% respectively) 5
• Single branch embolization is as effective as multiple branch embolization, with rescue surgery rates of 9.3% vs 7.8% 5
• Target any accessible location in the MMA to achieve sufficient flow restriction for spontaneous hematoma resolution 5

Embolic Agent Selection

Both Onyx (ethylene vinyl alcohol) and polyvinyl alcohol particles (PVA) are equally effective 6:

• Failure rates: Onyx 12.2% vs PVA 25.0% (not statistically significant, p=0.112) 6
• Rescue surgery rates: Onyx 10.2% vs PVA 16.7% (not statistically significant, p=0.354) 6
• PVA may result in smaller residual hematoma thickness at late follow-up (4.6mm vs 7.8mm) 6
• Both agents can be used safely without increased complication rates 6

Post-Procedure Management

Immediate Post-Procedure Care

• Remove sheath early after procedure to reduce risk of clot formation 1
• Apply manual pressure 2-3 cm proximal to puncture site during sheath removal to achieve hemostasis 1
• Correct coagulopathies before sheath removal in anticoagulated patients 1

Monitoring Protocol

• Minimum 24-hour neurological monitoring to detect complications 1
• Same-day discharge is possible with transradial approach in uncomplicated cases 2
• Patients with complex medical histories require more intensive monitoring 1

Follow-Up Imaging

• Day 1: Initial post-procedure assessment 3
• 2 weeks: Early response evaluation 3
• 6 weeks: Definitive outcome assessment 3
• Additional intervals as clinically indicated 3

Expected Outcomes

Primary Treatment Success

When used as primary therapy for new or recurrent cSDH:

• 91.1% of patients avoid surgical evacuation with stable or decreased hematoma size 3
• 68.9% achieve resolution or >50% size reduction at longest follow-up 3
• Recurrence requiring surgery: 8.9% 3

Adjunct to Surgery

When combined with surgical evacuation:

• Significantly lower treatment failure compared to surgery alone 4
• Reduced reoperation rates by 55% 4
• 50% reduction in 30-day readmissions 4
• No increase in complications or mortality compared to surgery alone 4

Complications and Safety

• No procedural complications reported in the largest single-center series of 60 cases 3
• Treatment-related complications are comparable to surgery alone (OR 0.89) 4
• Mortality rates equivalent to surgery alone (OR 1.05) 4
• Common complications to monitor:
  • Access site complications (hematoma, pseudoaneurysm) 1
  • Thromboembolic events 1
  • Vessel perforation or rupture 1

Clinical Pitfalls

• Do not delay treatment in patients with mass effect or progressive symptoms—MMA embolization provides rapid symptom relief 2
• Assess for cross-calvarial supply from contralateral MMA or accessory meningeal vessels before planning unilateral embolization 2
• Tailor embolization when multiple meningeal vessels supply the hematoma 2
• Avoid over-planning the specific branches to embolize—any MMA location provides sufficient flow restriction 5
• Consider prophylactic embolization immediately after surgical evacuation in high-risk patients for recurrence 3