Sealing the Leak: MMA Embolization for Chronic Subdural Hematoma
When an 88-year-old man experienced several falls and began developing right-sided weakness, it wasn’t immediately clear how serious the situation was. But a CT scan at Morristown Medical Center told a different story: a large chronic subdural hematoma (cSDH) causing pressure on the brain.
For this patient — and for thousands of aging Americans — cSDH represents a frustrating medical challenge. The condition occurs when small veins tear between the brain and its protective outer layer (known as the dura mater), causing bleeding that builds up over days or weeks.
Dr. Guilherme Barros, a neurosurgeon specializing in cerebrovascular and endovascular procedures at Atlantic Brain and Spine (ABS), explained:
“Chronic subdural hematoma is becoming increasingly common as people live longer and rely on blood thinners for other conditions. As the brain ages, it naturally shrinks, weakening the surrounding veins and making them more likely to bleed with minor head injuries.”
Traditional treatment requires surgical drainage through burr holes or craniotomy to relieve the bleeding. But for up to one third of patients, the hematoma can come back, causing additional anxiety about recurrence and additional surgery.
Now, an innovative, minimally invasive endovascular procedure called middle meningeal artery (MMA) embolization promises to break that cycle — providing select patients a safe, lasting solution for cSDH.
The Problem: A Frustrating Cycle
For decades, neurosurgeons have treated cSDH the same way: drill through the skull, release the collected blood, and relieve pressure on the brain. They may place small, temporary drains to prevent fluid from returning in the days after surgery.
The problem is that traditional surgery addresses the effect, not the cause, of the bleeding. Fragile membranes supplied by the middle meningeal artery form along the dura’s surface in cSDH, which may continue to ooze blood and fluid even after draining.
Schematic representation of pertinent vasculature off common carotid artery.
It’s a bit like mopping up a puddle without fixing the leak. Some patients — especially those on blood thinners — can wind up back in the hospital weeks or months after surgery, facing the same problem as before and potentially requiring repeat surgery.
The toll extends beyond the operating room. Multiple surgeries mean more hospital stays, mounting complications and growing anxieties. For many older adults, hospitalization comes with additional risks, including:
- Infections
- Loss of independence
- Financial burden
The patient, who had a history of atrial fibrillation and was at elevated risk due to repeated falls, faced this uncertain future. Dr. Barros explained the options to the patient and his family: observation, traditional surgery or MMA embolization — an endovascular technique designed to stop the blood leak at its source.
Wanting to minimize recurrence risk and support recovery, the patient and his family elected to proceed with embolization in combination with burr hole drainage.
The Solution: Turning Off the Faucet
In chronic subdural hematoma, tiny branches of the middle meningeal artery supply blood to the thin membranes that develop along the dura mater. These membranes are fragile and full of tiny new blood vessels that can keep leaking long after the original injury and treatment.
MMA embolization closes off the small arterial branches feeding the membranes — turning off the proverbial faucet and preventing future leaks.
Schematic representation of subdural hematoma.
Through a small puncture in the femoral or radial artery, a neurosurgeon guides a microcatheter through the blood vessels and into the MMA under contrast-enhanced Xray guidance. Once positioned, the surgeon inserts embolic materials such as:
- Medical adhesive (NBCA)
- Embolic liquids like SQUID, Onyx, and PHIL
- Microparticles
- Helical coils
These agents seal the branches feeding the hematoma membranes and stop them from growing and leaking. The body then reabsorbs the membrane naturally.
Cerebral angiogram demonstrating selective catheterization of the middle meningeal artery prior to embolization, highlighting the vascular supply to membranes associated with chronic subdural hematoma.
The entire procedure takes one to two hours and requires no skull incision or stitches. Many patients return home the next day.
MMA embolization alone can be used to treat smaller, manageable bleeds, but can be used in combination with surgical techniques for larger hematomas requiring evacuation.
In this case, Dr. Barros performed SEPS drainage followed by MMA embolization, using NBCA (medical glue) and coils to seal the vessels feeding the hematoma membranes. The patient progressed well without complications. The SEPS drain was removed two days later, and the patient was discharged to acute rehabilitation before returning home with support.
The Evidence: Promising Results
Early studies in the United States and Japan had hinted that MMA embolization could reduce recurrence rates in chronic subdural hematoma. However, hints aren’t enough to change medical practice. Two landmark trials, both published in 2024, provided proof of its efficacy.
The EMBOLISE Trial (U.S., 2023-2024)
Conducted across multiple centers, EMBOLISE enrolled 400 patients with symptomatic subacute or chronic subdural hematoma requiring surgery. Half received MMA embolization with Onyx liquid embolic plus standard care; half had standard care alone.
The results were striking: adding embolization cut recurrence risk by more than half without worsening recovery. Just 4.1% of embolization patients required repeat surgery compared to 11.3% of the controls. The procedure was safe, with serious adverse events occurring in only 2% of cases.
The STEM Trial (International, 2024)
The global STEM trial evaluated embolization using a non-adhesive liquid embolic agent known as SQUID. The study enrolled 310 patients randomized to either embolization plus burr-hole surgery, or surgery alone.
Dr. Ronald Benitez, endovascular neurosurgeon at ABS and the medical director of endovascular neurosurgery at Atlantic Health System, treated the first STEM patient in New Jersey, marking a milestone for the study.
In the study, failure rates dropped from 36% in the control group to just 16% in the patients who received embolization. Safety profiles were comparable, with 3% of patients in both groups experiencing serious adverse advents.
“Trials like STEM and EMBOLISE are changing how we think about chronic subdural hematoma,” said Dr. Barros. “The results confirm what we’re seeing in practice – fewer recurrences and repeat surgeries, faster recoveries, and better outcomes.”
MEMBRANE, another recent study in the U.S., looked at the effect of MMA embolization with NBCA glue. Preliminary results continue to strengthen the case for middle meningeal artery embolization in the treatment of chronic subdural hematoma, reporting reduction in reoperation or significant recurrence by about 50%. While the analysis found a treatment effect across all age groups, the most significant effect was in patients over the age of 75.
Across these trials, embolization has shown promise in reducing recurrence and need for further surgery in patients with cSDH. Researchers are now exploring its use beyond cSDH, including potential applications for chronic migraine headaches.
A New Paradigm for Chronic Subdural Hematoma Treatment
Initial patient CT scan
Initial patient CT scan showing a large chronic subdural hematoma causing pressure on the brain.
Three-month post-operative CT scan
Three-month post-operative patient CT scan showing the chronic subdural hematoma resorbing over time.
At the patient’s three-month follow-up, imaging showed the chronic subdural hematoma continuing to resorb over time, with minimal mass effect on the brain and no significant recurrence compared to immediate post-operative scans.
“It was reassuring to see him doing so well and his scans improving and to know there was a reduction in the chance of this happening again,” a family member said.
For patients with chronic subdural hematoma, the advantages of MMA embolization with or without surgery over surgery alone can be substantial:
- Lower risk of repeat surgeries and hospitalizations
- Lower risk of significant recurrence of cSDH
- Relief that their risk has been minimized
Personalization is key. Some patients will still require surgery, especially when the hematoma causes severe pressure on the brain. Others can safely undergo embolization alone without further intervention. Still more may require a combination of both.
“Each patient’s anatomy, medical history, and goals shape the best approach,” emphasized Dr. Barros. “Innovation must always serve the patient, not the other way around.”
Across the field, more centers are adopting hybrid treatment models combining surgery and embolization for complex cases. Early data suggests MMA embolization could eventually become first-line treatment for many patients (with or without surgery), replacing surgical drainage alone as the standard of care.
An Evolving Approach to Neurosurgery
This shift reflects a broader transformation in neurosurgery that favors minimally invasive approaches. For certain brain conditions, precise endovascular techniques offer safe and effective alternatives to traditional open surgery.
Dr. Barros believes cases like this mark a turning point in how neurosurgeons think about chronic subdural hematoma and other conditions.
“We’re learning to treat cSDH not just as a structural problem, but as a vascular condition,” he explained. “This changes everything from how we plan treatment to how patients heal.”
For aging populations, this evolution is vital. As more people take blood thinners to prevent stroke or heart disease and life expectancy rises, the number of cSDH cases will continue to climb. MMA embolization offers a path towards sustained healing for patients with cSDH.
Advanced Care for Chronic Subdural Hematoma
Atlantic Brain and Spine offers advanced neurosurgical and endovascular treatment options for patients with chronic subdural hematoma and other complex brain conditions.
Request an appointment with Atlantic Brain and Spine to learn more about available treatment options.
