What is the procedure and considerations for Middle Meningeal Artery (MMA) embolization?

Middle Meningeal Artery (MMA) Embolization: Procedure and Considerations

MMA embolization is an effective endovascular procedure for treating chronic subdural hematomas (cSDH), with significantly lower recurrence rates compared to surgical evacuation alone (4.5% vs historical rates of 10-20%). 1

Procedure Overview

• MMA embolization involves catheter-directed endovascular intervention to occlude the middle meningeal artery, which supplies blood to the outer membrane of chronic subdural hematomas 2
• The procedure is performed under either general anesthesia or deep intravenous sedation with neurological monitoring, depending on the specific case requirements 3
• Direct transduction of arterial pressure is indicated during the procedure, typically via the femoral artery introducer sheath 3, 2
• Additional monitoring includes pulse oximetry on both the treatment side and the foot of the leg receiving the femoral introducer catheter to detect potential complications 3, 4

Technical Aspects

• The procedure involves:
  • Femoral artery access with placement of an arterial sheath 4
  • Selective catheterization of the external carotid artery and then the middle meningeal artery 1
  • Superselective microcatheter navigation into the MMA 1
  • Infusion of embolic material, most commonly polyvinyl alcohol particles, though Onyx is also used 1, 5
• Early sheath removal is recommended after the procedure to reduce the risk of clot formation within the sheath 4
• Manual pressure is applied 2-3 cm proximal to the puncture site during sheath removal to achieve hemostasis 4

Clinical Applications

• MMA embolization can be performed in three main clinical scenarios:
  • Primary treatment for cSDH in minimally symptomatic patients 5
  • Treatment for recurrent cSDH after surgical evacuation 5
  • Prophylactic treatment in conjunction with surgical evacuation to prevent recurrence 1, 6
• The procedure has shown particular efficacy when combined with surgical evacuation, with studies showing reduced mortality, readmission rates, and reoperation rates compared to surgery alone 6

Efficacy and Outcomes

• Recent multi-institutional studies demonstrate that patients undergoing combined MMA embolization with surgical evacuation have significantly better outcomes than those with surgical evacuation alone 6
• Recurrence rates after MMA embolization are reported to be as low as 3.6-4.5%, compared to historical recurrence rates of 10-20% with surgical evacuation alone 1, 5
• The presence or absence of visible membranes on imaging does not appear to affect outcomes after MMA embolization, suggesting that membrane presence should not be the sole selection criterion 7

Complications and Monitoring

• Post-procedure neurological monitoring is essential for at least 24 hours to detect potential complications 2
• Continuous assessment of neurological and hemodynamic parameters is required during and after the procedure 2
• Common complications to monitor for include:
  • Access site complications (hematoma, pseudoaneurysm, retroperitoneal bleeding) 4
  • Thromboembolic events 3
  • Vessel perforation or rupture 3
• No significant procedure-related complications were reported in several large studies, suggesting a favorable safety profile 1, 5

Patient Selection and Considerations

• MMA embolization is particularly beneficial for:
  • Patients with recurrent cSDH after surgical evacuation 5
  • High-risk surgical patients with significant comorbidities 2
  • Patients undergoing surgical evacuation who would benefit from prophylactic embolization to prevent recurrence 1, 6
• Patients with coagulopathies require correction of coagulation parameters before sheath removal 4
• Patients with complex medical histories and recent neurological events require more intensive post-procedural monitoring 2

Pitfalls and Caveats

• Overly vigorous compression during sheath removal can cause vessel occlusion; this can be avoided by monitoring distal pulses during compression 4
• Improper identification of the puncture site can be avoided by using anatomical landmarks or ultrasound guidance 4
• Early recognition of complications requires vigilant monitoring of the access site and distal circulation 4
• For patients requiring anticoagulation, careful planning of the timing of medication cessation and resumption is essential 4