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

Middle Meningeal Artery (MMA) Embolization: Procedure and Management

Indications for MMA Embolization

MMA embolization is indicated for chronic subdural hematoma (cSDH) as either primary treatment, adjunctive therapy with surgical evacuation, or for recurrent hematomas after conventional surgery. 1, 2, 3

• Primary treatment: Appropriate for relatively asymptomatic patients with cSDH who can avoid surgical evacuation 3, 4, 5
• Perioperative adjunct: Performed in conjunction with surgical evacuation (craniotomy or burr hole drainage) to reduce recurrence rates 3, 6
• Recurrent hematomas: Effective for patients with one or more recurrences after conventional surgery 4, 6, 7
• Prophylactic use: Can be performed after surgical evacuation to prevent recurrence 3, 7

Pre-Procedure Considerations

• Patient selection factors: Older age, antiplatelet drug use, severe brain atrophy, and bilateral hematomas are associated with need for embolization 6
• Coagulation management: Patients on anticoagulation (23.9%) or antiplatelet therapy (30.4%) can undergo the procedure, though coagulopathies should be corrected before arterial sheath removal 2, 4
• Anesthesia choice: The procedure can be performed under general anesthesia (46.1% of cases) or deep intravenous sedation with neurological monitoring 2, 4

Technical Procedure Details

Access and Catheterization

• Femoral artery access is obtained with placement of an arterial introducer sheath 2
• Direct arterial pressure transduction is performed via the femoral sheath 2
• Selective catheterization of the MMA branches is performed under fluoroscopic guidance 3, 6

Embolic Agents

• Polyvinyl alcohol (PVA) particles are the most commonly used embolic agent (70.2% of procedures) 3, 4, 5
• Liquid embolics (Onyx) are used in 25.3% of cases with no significant outcome difference compared to particles 4, 7
• Target vessels: Two branches of the MMA supplying the external membrane of the cSDH are typically selected for occlusion 6

Monitoring During Procedure

• Pulse oximetry should be placed on both the treatment side and the foot of the leg receiving the femoral catheter to detect thromboembolic complications 2
• Continuous neurological assessment is required throughout the procedure 2
• Hemodynamic monitoring with arterial pressure transduction is maintained 2

Post-Procedure Management

Immediate Post-Procedure Care

• Neurological intensive care monitoring for at least 24 hours is essential to detect potential complications 1, 2
• Early sheath removal is recommended after the procedure to reduce risk of clot formation 2
• Manual pressure is applied 2-3 cm proximal to the puncture site during sheath removal to achieve hemostasis 2
• Normotensive and euvolemic conditions should be maintained post-procedure 1

Monitoring Parameters

• Continuous neurological examination for at least 24 hours 1, 2
• Blood pressure monitoring with maintenance of normotensive parameters 1
• Access site assessment for bleeding, hematoma, or vascular complications 2
• Watch for thromboembolic events and vessel perforation or rupture 2

Clinical Outcomes and Efficacy

Radiographic Response

• Median hematoma thickness reduction: 71-77.5% at last follow-up 4, 5
• >50% thickness reduction: Achieved in 70.8-72.8% of patients 4, 5
• Median time to assessment: Approximately 90-95 days post-procedure 4, 5

Recurrence Rates

• Overall recurrence requiring retreatment: 3.6-13.8% across studies 4, 5, 7
• Perioperative embolization with craniotomy: 0% recurrence rate in one series of 26 patients 3
• Primary embolization alone: 13.8% retreatment rate 5
• Significantly lower than historical surgical evacuation alone (typically 10-30% recurrence) 3, 6

Clinical Improvement

• Symptomatic improvement: 31.9-49.3% of patients show clinical improvement 4, 5
• Modified Rankin Scale improvement: Observed in 49.3% of patients 5

Complications and Safety Profile

Procedural Success and Complications

• Technical success rate: 97.4-100% of procedures successfully completed 4, 5, 7
• Procedure-related complications: 2.8-6.5% 4, 5
• Continued hematoma expansion: Most common complication (6.5% of cases) 4
• No reported major neurological complications in systematic reviews 7

Mortality

• Mortality rate: 4.4-8.4%, primarily from underlying comorbidities unrelated to the procedure 4, 5

Common Pitfalls and Caveats

• Timing of surgical evacuation: When combining embolization with surgery, perform embolization perioperatively (immediately before or after evacuation) to maximize benefit 3
• Patient selection: High-risk surgical patients with significant comorbidities benefit most from primary embolization without surgical evacuation 2, 5
• Bilateral hematomas: Each side requires separate embolization; 15 patients in one series underwent bilateral interventions 4
• Anticoagulation management: Patients can remain on antiplatelet or anticoagulation therapy during the procedure, but correction may be needed for sheath removal 2, 4
• Follow-up imaging: Serial CT imaging at 90 days is standard to assess hematoma resolution 4, 5