Middle meningeal artery (MMA) embolization is a treatment for chronic subdural hematoma, or persistent bleeding on the surface of the brain. This nonsurgical technique removes the blood that has collected between the brain and its protective tissue layer, the dura mater, and generally prevents the problem from coming back.

Chronic subdural hematoma is one of the most common neurosurgical conditions affecting older people. It can occur after an injury or medical problem that causes bleeding between the dura and the brain, an area known as the subdural space.

Normally, if blood leaks into the subdural space, the body responds by forming a thin membrane around this blood. The membrane has tiny blood vessels that allow the immune system to break down the pooled blood and remove it. But the membrane itself is also leaky; in some people, the blood leaks back out more quickly than it can be absorbed. The result is a pool of blood accumulating on the brain's surface: a chronic subdural hematoma.

This problem can cause a range of symptoms, including headaches, confusion, loss of balance, and weakness on one side of the body. If untreated, the increasing pressure on the brain can lead to seizures, coma and even death.

The traditional treatment for chronic subdural hematoma is surgical: Two holes are drilled into the skull and a hollow tube is inserted to drain the blood. The operation can be risky, and patients have to stay in intensive care for a few days while the hematoma is draining. What's more, 1 in 4 patients has a recurrence within a month and must return to the hospital for additional treatment.

MMA embolization offers a minimally invasive, highly effective alternative. Instead of traditional surgery, doctors use specialized tools that pass through blood vessels to access and block an artery supplying blood to the dura and the membrane surrounding the hematoma. Once it's closed off, blood stops leaking into the subdural space and, over time, the body absorbs the hematoma.

UCSF is a national leader in endovascular procedures (minimally invasive techniques to address problems with blood vessels). In particular, our specialists helped develop groundbreaking approaches to diagnosing and treating disorders affecting blood vessels of the brain, neck and spine.

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Who is a candidate?

MMA embolization isn't an option for everyone with a chronic subdural hematoma. It's appropriate under the following circumstances:

  • The patient has a chronic subdural hematoma but only mild or moderate symptoms. Instead of needing surgery right away, these patients have the time to undergo MMA embolization and wait for the hematoma to resolve.
  • The patient requires immediate surgery for a chronic subdural hematoma but is at risk for recurrence because of brain atrophy, liver or kidney failure, or needing to be on blood-thinning medication for another problem. In those cases, we will perform surgery and embolization at the same time.
  • The patient had surgery to drain a chronic subdural hematoma but the problem recurred.


MMA embolization offers many advantages over traditional surgery, including:

  • It can be done on an outpatient basis (patients don't have to stay overnight in the hospital), with little or no sedation.
  • It causes less discomfort and requires only one small incision.
  • The risk of complications is lower.
  • Patients recover quickly, with almost no downtime.
  • It addresses the problem's root cause: the leaky membranes.
  • The hematoma rarely recurs. This happens in only 2 to 3% of cases, compared with a 25% recurrence rate for conventional surgery.


MMA embolization is performed in one of our angiogram suites, which are specially equipped for procedures that involve working through the blood vessels. Prior to the procedure, you receive a mild sedative that leaves you relaxed but awake. The endovascular neurosurgeon numbs the skin at either your wrist or groin to access the artery and inserts a catheter (a thin, flexible tube).

Guided by X-ray images, the surgeon threads the catheter through your blood vessels until it reaches the middle meningeal artery, near the hematoma. The surgeon then injects an agent that permanently closes off the artery; this may be a special glue, certain kinds of particles, or platinum micro coils. After the embolization is complete, the surgeon withdraws the catheter and closes the incision. The whole procedure typically takes 45 minutes to an hour. You should be able to go home after about two hours.


You can resume your normal activities immediately. The only issue afterward is making sure the incision site stays dry and clean as it heals.

Though recurrence is unlikely, we'll monitor your progress with follow-up CT scans at six and 12 weeks.

Possible complications

Risks include bleeding, infection, stroke, pain and vision problems, but these complications are rare, occurring in only about 1% of patients.