Middle Meningeal Artery Embolization in Chronic Subdural Hemorrhage

The membranes, vascular networks, and brain tissue inside our skull work in a highly complex harmony to protect the brain. However, sometimes these balances can be disrupted, and unwanted blood or fluid may accumulate around the brain for various reasons. A typical example of this pathology is “chronic subdural hemorrhage.” Although traditional surgical methods are still applied today to treat chronic subdural hemorrhage (CSDH), especially in recurrent cases or certain high‑risk patient groups, a new and less invasive method called “Middle Meningeal Artery Embolization” has increasingly attracted attention.

What Is Chronic Subdural Hemorrhage?

Chronic subdural hemorrhage is the accumulation of blood or fluid between the dura mater—the thick membrane covering the brain—and the brain surface. It can develop after mild or severe head trauma, small tears in tissue over time, or weakening of brain‑covering tissues in elderly patients. The term “subdural” refers to the potential space beneath the dura and above the arachnoid membrane. Accumulation in this space exerts pressure on the brain tissue. In some patients, this pressure causes obvious neurological deficits; in others, it develops slowly and insidiously, producing only mild symptoms.

Why “Chronic”?

“Chronic” means “long‑lasting” or “slowly developing.” In chronic subdural hemorrhage, fluid typically accumulates over weeks to months. Unlike acute subdural hemorrhage, severe symptoms do not appear suddenly; instead, patients may experience mild headache, imbalance, slight confusion, or drowsiness over time. In elderly patients, natural brain volume loss facilitates fluid accumulation in the subdural space.

Common Symptoms

Symptom severity depends on fluid volume and patient health. Common findings include:

• Persistent or chronic headaches
• Inattention and mental cloudiness
• Mild memory problems
• Gait disturbances, imbalance
• Occasional limb weakness

Because symptoms progress slowly, patients and families may attribute them to “aging” or “chronic fatigue.” Regardless of trauma history, these signs should prompt medical evaluation.

Why Do We Need This New Method?

Although surgical evacuation (burr‑hole drainage or craniotomy) remains the gold standard for chronic subdural hemorrhage, these interventions carry their own challenges and recurrence risks. Recurrence rates after traditional surgery range from 11% to 33%. In elderly patients or those with comorbidities (heart, lung, kidney disease, coagulopathy), repeat operations and anesthesia pose significant risk.

Middle meningeal artery embolization (MMAE) has emerged as a less invasive alternative. The subdural membrane that sustains chronic hematoma develops fragile neovessels, primarily fed by the MMA. By occluding the MMA, we effectively “turn off the tap,” preventing further leakage. While large, high‑pressure hematomas still require surgical evacuation, growing evidence suggests that in mild or recurrent cases, MMAE offers a safer, less invasive option with lower recurrence rates.

Pathophysiology of Chronic Subdural Hemorrhage

Normally, the dura mater adheres to the skull’s inner surface, separated from the arachnoid by a potential space. Trauma can cause bridging veins to leak blood into this space. If not cleared, a chronic process ensues, forming a capsule (membrane). Within this membrane, new, fragile vessels develop (neovascularization), prone to leakage. These vessels are largely branches of the MMA. As chronic hemorrhage progresses, the MMA’s fragile branches perpetuate bleeding or fluid seepage.

What Is MMA Embolization?

Embolization means occluding an unwanted vessel to stop blood flow. A catheter is navigated to the MMA, and embolic materials (particles, liquid agents) are injected to occlude the vessel and its branches feeding the hematoma.

Procedure Steps

• Vascular Access: A small puncture is made in the femoral artery. A guide catheter is advanced to the aorta, then into the external carotid and MMA.
• Angiography: Contrast injection maps MMA branches, checking for dangerous collaterals (e.g., orbital or facial nerve branches).
• Embolic Injection: Particles (e.g., 150–250 µm) are injected to occlude target branches. Injection continues until flow stasis.
• Control Angiogram: Post‑embolization angiography confirms vessel occlusion. Catheters are removed, and the access site is closed.

Mild sedation often suffices, though general anesthesia may be used if necessary.

Why Target the MMA?

Because the subdural membrane’s neovessels are primarily supplied by the MMA. Occluding this artery “shuts off” the fragile vessels’ blood supply, halting further bleeding or fluid seepage.

Current Research and Statistics

Although large randomized controlled trials are lacking, case series and retrospective studies report:

• Recurrence Rates: Traditional surgery sees 11–33% recurrence. Early results suggest MMAE recurrence rates are much lower.
• Patient Profiles: Particularly beneficial for patients with multiple prior surgeries or those requiring anticoagulation, allowing continuation of their medications without interruption.
• Clinical Improvement: Small studies show hematoma regression and neurological improvement post‑embolization.
• Need for Larger Trials: Definitive conclusions await multicenter randomized trials comparing embolization to surgery.

Note: Not all cases can be treated with embolization alone. Large, high‑pressure hematomas may still require surgical evacuation, with embolization used adjunctively or in a hybrid approach (evacuation followed by MMAE).

Advantages and Risks

Advantages

• Minimally invasive via groin or arm artery, less physical stress than craniotomy.
• Often performed under mild sedation; patients may be discharged within 24 hours.
• May allow continuation of anticoagulants in high‑risk patients.
• Early data suggest lower recurrence than surgery.
• Better tolerated by elderly or medically frail patients.

Risks

• Non‑target embolization can cause stroke or vision loss if particles reach unintended vessels.
• Complex MMA anatomy may lead to incomplete occlusion.
• Large hematomas may not decompress rapidly enough—surgery remains life‑saving.
• Long‑term outcomes and success rates require more extensive data.
• Repeat procedures carry similar risks.

Anatomical Considerations

MMA branching patterns vary. Dangerous collaterals include:

• Petrosal branch near the facial nerve—embolization may risk facial palsy.
• Orbital branch connecting to ophthalmic artery—embolization may risk vision loss.

Super‑selective catheterization and low‑pressure pulsatile injections under live angiography minimize these risks.

Post‑Procedure Follow‑Up

Patients are monitored neurologically and may undergo CT or MRI within 24 hours. Expected findings:

• Transient increased density on CT from contrast retention, not to be confused with rebleeding.
• Mild headache or pressure sensation, usually self‑limiting.
• Stable or improved neurological status. Large hematomas may still require surgery if mass effect persists.

Follow‑up imaging at 2 and 6 weeks assesses hematoma regression, which can occur gradually over weeks to months.

Patient Selection

Not every patient is a candidate. Considerations include:

• Hematoma size and mass effect—large, symptomatic hematomas require urgent surgery.
• Neurological deficits or altered consciousness—surgical decompression prioritized.
• MMA anatomy—tortuous or hazardous collaterals may contraindicate embolization.
• Comorbidities—embolization often better tolerated than surgery in high‑risk patients.
• Recurrent cases—multiple prior surgeries favor embolization as a safer alternative.

Possible Complications

• Access site bleeding or hematoma.
• Stroke from non‑target embolization.
• Allergic reactions to contrast or embolic agents.
• Facial nerve injury from petrosal branch embolization.
• Vision loss from orbital branch embolization.

These complications are rare but must be discussed with the patient.

Return to Daily Life

Most patients are discharged within 1–2 days if no complications arise. Recommendations:

• Avoid heavy lifting or strenuous activity for several days.
• Attend scheduled follow‑up imaging (CT or MRI).
• Manage anticoagulant therapy per physician guidance.
• Monitor headache and neurological symptoms; report any worsening.
• Implement fall‑prevention measures at home and maintain blood pressure control.

Will This Become Standard?

The neurosurgical and interventional neuroradiology communities await large randomized trials comparing MMAE to surgery. Current evidence supports MMAE in recurrent or high‑risk patients, and hybrid approaches (surgery plus embolization) show promise. As experience grows, MMAE may become a standard adjunct or alternative in selected cases.

Patient Decision‑Making

There is no one‑size‑fits‑all treatment. Decisions depend on hematoma characteristics, patient age, comorbidities, medication use, and surgical risk. MMAE offers a “turn off the tap” strategy that may benefit patients with recurrent hemorrhage or high surgical risk. However, it requires specialized expertise and carries its own risks. Multidisciplinary evaluation by neurosurgeons, interventional neuroradiologists, and neurologists is essential to determine the best approach for each individual.

Prof. Dr. Özgür KILIÇKESMEZ

Prof. Dr. Özgür Kılıçkesmez graduated from Cerrahpaşa Medical Faculty in 1997. He completed his specialization at Istanbul Education and Research Hospital. He received training in interventional radiology and oncology in London. He founded the interventional radiology department at Istanbul Çam and Sakura City Hospital and became a professor in 2020. He holds many international awards and certificates, has over 150 scientific publications, and has been cited more than 1500 times. He is currently working at Medicana Ataköy Hospital.