How MMA embolisation treats brain bleeds without opening the skull

For decades, when a subdural hematoma became large enough to compress the brain, the treatment pathway was relatively straightforward: surgeons would make an opening in the skull and drain the accumulated blood.

A newer approach is changing that equation for a carefully selected group of patients.

Middle meningeal artery embolisation, or MMA embolisation, is a minimally invasive endovascular procedure in which doctors navigate a thin catheter through the blood vessels to the middle meningeal artery, a vessel that supplies the membrane surrounding the brain, and block selected branches feeding the abnormal membrane associated with a subdural hematoma.

The idea is deceptively simple: instead of directly removing the blood collection, stop the process that helps sustain and replenish it.

The technique has gained considerable attention in recent years, particularly in the treatment of chronic subdural hematoma (CSDH), and emerging randomised-trial evidence suggests that it can reduce treatment failure and recurrence in appropriately selected patients. It is increasingly being used either as an alternative to surgery in selected cases or alongside surgical drainage.

A recent case at Gleneagles Hospital, Parel, Mumbai, illustrates how the approach is being used in clinical practice.

A 67-year-old doctor from Jabalpur, who was taking blood-thinning medication for a heart condition, presented with weakness on one side, imbalance, confusion and altered sensorium. Imaging reportedly showed a 22-mm-thick subdural hematoma with a 14-mm midline shift, indicating significant pressure on the brain.

Given the size of the collection and the pressure it was causing, conventional surgery would ordinarily be considered. But the patient was reluctant to undergo an open procedure.

Doctors instead performed MMA embolisation.

According to the treating team, the procedure took approximately 30 minutes. The patient improved the following day clinically, with the hematoma subsequently shrinking from 22 mm to 6 mm over about a month and reportedly disappearing by six weeks. He has since returned to his home and resumed his clinical practice.

A subdural hematoma occurs when blood accumulates between the brain's outer covering, the dura, and the surface of the brain. In older adults, the condition can develop after relatively minor trauma because age-related brain shrinkage places greater tension on the small veins that cross this space.

Some hematomas, particularly chronic ones, do not simply remain as an old pocket of blood.

Over time, the body forms a membrane around the collection. This membrane can develop a network of fragile, abnormal blood vessels. These vessels are prone to leakage and repeated small bleeds, while inflammatory processes can also contribute to continued enlargement of the collection.

This helps explain an important problem with conventional drainage: removing the blood does not necessarily eliminate the biological process that caused the collection to persist.

The hematoma may therefore recur.

This is where the middle meningeal artery enters the picture.

The middle meningeal artery is one of the principal blood vessels supplying the dura, the tough membrane surrounding the brain.

In chronic subdural hematoma, branches of this artery can supply the vascularised membrane surrounding the collection.

MMA embolisation attempts to interrupt that blood supply.

The patient is generally taken to an angiography suite, where the procedure is performed under imaging guidance. A catheter is introduced into an artery, commonly through the wrist or groin, and carefully navigated through the arterial system towards the middle meningeal artery.

Once the artery and its relevant branches have been identified, the interventional neurovascular team injects an embolic material through the catheter.

Depending on the technique and device being used, this may consist of tiny particles or a liquid embolic agent.

The material travels into the targeted abnormal vascular network and blocks blood flow to it.

The catheter is then withdrawn. There is no need to open the skull.

And importantly, the embolisation does not mechanically suck out the existing hematoma. Instead, by reducing the blood supply to the pathological membrane and limiting the tendency for further leakage, the procedure is intended to create conditions in which the body can gradually resorb the existing collection.

MMA embolisation treats the vascular source associated with the persistence of the hematoma; the body does the job of clearing much of the blood that is already there.

MMA embolisation is not simply a replacement for emergency brain surgery.

A patient with a very large hematoma causing severe neurological deterioration or dangerous brain compression may require immediate decompression. In such circumstances, waiting for the collection to resolve gradually may not be appropriate.

Surgical drainage through burr holes or, in some situations, a craniotomy remains an important and sometimes lifesaving treatment.

MMA embolisation is particularly attractive in chronic or non-acute subdural hematomas, especially when recurrence is a concern, when a patient is at high risk from repeated surgery, or when the clinical and radiological circumstances allow time for the hematoma to regress.

It can also be used in combination with surgery. A surgeon may drain the existing collection to relieve pressure while embolisation is used to address the vascular membrane and reduce the likelihood of recurrence.

The decision depends on factors including the patient's neurological status, the age and characteristics of the hematoma, its size and mass effect, medical conditions, medications and the anatomy of the middle meningeal artery.

This is one of the reasons MMA embolisation has attracted particular interest.

Anticoagulant and antiplatelet medicines can complicate the management of subdural hematoma because doctors must balance the risk of bleeding against the risk of stopping medication that may have been prescribed to prevent stroke, heart attack or other serious cardiovascular events.

In the Jabalpur doctor's case, his treating team considered his use of blood thinners an important part of the treatment decision.

However, MMA embolisation should not be described as making blood thinners irrelevant or automatically eliminating the need to manage them. Antithrombotic management remains an individual clinical decision, depending on why the drug was prescribed and the patient's bleeding and clotting risks.

MMA embolisation has moved rapidly from an innovative intervention to a procedure supported by a growing body of clinical evidence.

Several randomised controlled trials published in recent years have evaluated the technique. Together, these studies have strengthened evidence that adding MMA embolisation to standard treatment can reduce treatment failure or recurrence in selected patients with chronic subdural hematoma.

The exact benefit varies according to the study design, patient population and whether embolisation was used alone or in combination with surgery.

That is why specialists caution against interpreting MMA embolisation as a universal substitute for surgery.

Instead, its significance may lie in changing the treatment strategy from simply draining a collection to also addressing the vascular biology that allows some chronic subdural hematomas to recur.

For the Jabalpur doctor, the attraction was particularly clear.

He was faced with a sizeable hematoma and significant midline shift, while also taking medication for a cardiac condition. According to the treating doctors, MMA embolisation allowed them to treat the underlying vascular component without performing an open cranial operation.

“He clinically improved the next day,” said Dr Nitin Dange, Director, Neurosurgery and Neuro-vascular Intervention, Gleneagles Hospital Mumbai.

Dr Kushal Bhatia, Consultant, Neurosurgery and Neuro-vascular Intervention, said the procedure involved introducing a thin catheter through a blood vessel and guiding it to the artery supplying the membrane around the brain. Embolic material was then delivered to block the abnormal blood supply.

The existing hematoma, meanwhile, was allowed to resolve naturally.

That is perhaps the most important conceptual shift offered by MMA embolisation.

The procedure does not attack the hematoma head-on. It attacks its blood supply.

And as evidence accumulates, that relatively simple change in strategy could give doctors another tool for managing a condition that has traditionally relied heavily on surgical drainage.

In this process, specifically, a catheter is introduced through an artery, usually in the wrist or groin. Using real-time X-ray imaging, the catheter is guided towards the middle meningeal artery. Angiography identifies the relevant branches supplying the abnormal membrane associated with the subdural hematoma. An embolic material is delivered through the catheter to block the targeted abnormal blood supply. With reduced vascular supply and less tendency for recurrent bleeding, the body gradually resorbs the existing hematoma. Clinical assessment and brain imaging are used to monitor reduction of the collection and neurological recovery.

As neurointerventional techniques and evidence continue to evolve, the treatment of subdural hematoma may increasingly involve a combination of approaches rather than a single approach for every patient.