MMA embolization cuts recurrence risk in chronic subdural hematoma, trials show

One in ten patients treated surgically for chronic subdural hematoma ends up back in the operating room. For some, the odds are closer to one in five. A growing body of trial data now suggests a catheter-based adjunct can cut that number significantly. Meanwhile a European guideline is taking shape.

Chronic subdural hematoma (cSDH) is a slow-growing collection of blood between the brain and its outer membrane. It predominantly affects older adults and is becoming more common as Europe's population ages. A minor fall, sometimes unnoticed, can trigger it. Symptoms range from headaches and gait disturbance to confusion and neurological deficits. Left untreated, it can be fatal. 

An important complement 

71-year-old patient with headaches and unsteady gait. Coronal MRI before embolization demonstrating a chronic subdural hematoma (cSDH).Prof. Dr. Markus Möhlenbruch/DGNRMiddle meningeal artery (MMA) embolization works by cutting off the blood supply to the hematoma membrane. A microcatheter, inserted via the groin or wrist, is advanced to the MMA, and liquid embolic material is injected to permanently occlude the vessel. Without that blood supply, the membrane can no longer sustain the hematoma, which then resolves more readily. 

"Embolization will not fully replace surgery, as it does not provide immediate pressure relief," said Prof. Dr. Markus Möhlenbruch, professor of interventional neuroradiology and head of the Minimal Invasive NeuroTherapy Center (MINTZ) at Heidelberg University Hospital in Germany, according to the press release issued today by the German Society for Neuroradiology (DGNR). "But in many cases it can be an important complement, especially to prevent recurrence." 

Clinical benefits confirmed

Five randomized trials -- STEM, EMBOLISE, MEMBRANE, OTEMACS, and EMMA-CAN -- now point in the same direction. In the EMBOLISE trial, the 90-day recurrence rate dropped from 11.3% with surgery alone to 4.1% when embolization was added. The STEM trial showed rates of repeat hematoma or reoperation at 16% with embolization versus 36% under standard care. Serious embolization-related complications occurred in fewer than 2% of cases across available data. 

71-year-old patient with headaches and unsteady gait. Flat-detector CT (FDCT) after embolization showing the administered embolic agent.Prof. Dr. Markus Möhlenbruch/DGNRThe imaging picture behind those numbers has also come into sharper focus. A post-hoc analysis of the EMBOLISE trial, published in January in Radiology, found that adjunctive MMA embolization resulted in significantly lower hematoma volumes at both 90 and 180 days compared with surgery alone, with roughly 25% greater volume reduction at the 90-day mark. 

"The clinical benefits of adjunctive middle meningeal artery embolization are reflected in radiologic outcomes," wrote lead author Dr. Helge Kniep, of University Medical Center Hamburg-Eppendorf in Germany, and colleagues in that study.

Patient selection matters. In rare cases, anatomical connections between the MMA and the ophthalmic artery exist, and in those patients the procedure is generally avoided due to the risk of visual complications. 

Expanding the patient population

71-year-old patient with headaches and unsteady gait. Follow-up MRI three months after embolization showing marked regression of the hematoma; the patient is clinically symptom-free.Prof. Dr. Markus Möhlenbruch/DGNRThe evidence base is also extending to groups traditionally excluded from trials. A retrospective analysis published in January in the Journal of Vascular and Interventional Radiology, looked at coil-only MMA embolization in 30 cancer patients, a population at elevated risk for cSDH but routinely left out of landmark studies. 

Median hematoma thickness declined from 12 mm before the procedure to 3.6 mm, and patients whose hematomas reduced by 50% or more had a median survival of 148 days compared with 29 days in those without reduction. Only one patient required surgery due to persistent symptoms. 

The authors were cautious about generalizability given the high-risk cohort, and called for larger prospective studies.

A specific advantage for anticoagulated patients 

The relevance may be greatest for patients on anticoagulation therapy, a large and growing group that includes people with atrial fibrillation, prosthetic heart valves, or a history of stroke or myocardial infarction. For them, surgical treatment of cSDH creates a difficult tradeoff: stopping anticoagulation raises the risk of thrombotic events, but continuing it raises surgical bleeding risk.

Embolization offers a way through. "For this patient group, embolization can be an important component of treatment," Möhlenbruch said. "It can help reduce the risk of recurrence and allows necessary medications to be restarted much sooner."

Guideline on the way

The DGNR noted in its press release that the evidence base is moving fast. Several large international trials have recently published or are still running, and a European guideline on cSDH management is currently being developed. 

MMA embolization has rapidly transitioned from an experimental technique to an evidence-based adjunct, as the editorial accompanying the Radiology study put it. And the framework to standardize practice is catching up.