Brain Aneurysm Treatment: Coiling, Clipping and Beyond

Brain aneurysm treatment secures a ruptured aneurysm in one of two ways: surgical clipping, in which a neurosurgeon opens the skull and places a clip across the aneurysm's neck, or endovascular coiling, in which soft metal coils are delivered by catheter to fill the aneurysm from inside. Where an aneurysm suits both, current guidelines prefer coiling. Wide-necked or complex aneurysms need balloons, stents, intrasaccular devices or flow diverters.

Dr. Tariq Matin, Director & Chief, Neurointerventional Surgery, Artemis Hospitals, Gurugram, India, treats these patients as part of a team with his neurosurgical colleagues. This article covers haemorrhagic stroke in its main forms, subarachnoid haemorrhage and how aneurysms are secured, the techniques for difficult aneurysms, why aneurysms form, how arteriovenous malformations behind lobar bleeds are embolised, and what recovery looks like. The specialty as a whole is introduced in the complete guide to the role of neuro intervention; blocked arteries and veins are covered in the article on ischaemic stroke treatment and time windows.

Haemorrhagic stroke: where the bleed is decides the treatment

A haemorrhagic stroke occurs when a blood vessel ruptures and bleeds into or around the brain. In Dr. Matin's figures, haemorrhagic strokes make up 15% of all strokes, and aneurysmal subarachnoid haemorrhage around 3 to 4%. The location of the blood is the first clue to the cause.

• Deep bleeds sit in the structures deep within the brain. They are primarily caused by long-standing hypertension. The treatment is to bring the blood pressure down and prevent the haematoma (the collection of blood) from expanding; a larger bleed may need surgical decompression. These are managed medically or surgically, not by neurointervention.
• Subarachnoid haemorrhage is blood in the subarachnoid space, the fluid-filled layer that surrounds the brain beneath its membranes. Most of the time it comes from a ruptured aneurysm.
• Lobar bleeds lie in the outer lobes of the brain. They may arise from an underlying arteriovenous malformation or from venous thrombosis, and they warrant a search for that cause.
• Subdural bleeds collect beneath the dura, the tough outer covering of the brain.

Neurointervention plays its role in the last three: subarachnoid, lobar and subdural bleeds. For chronic subdural haematoma, the established endovascular option is embolisation of the middle meningeal artery, which supplies the membranes in which these collections recur.

When a bleed must be evacuated

Asked whether he evacuates an intracerebral haematoma manually or with robotic or stereotactic guidance, Dr. Matin first corrected a common assumption: not every intracerebral haemorrhage goes under the scalpel or receives endovascular treatment. The bleed is diagnosed on neuroimaging, with CT or a good MRI, and two questions follow. Why did the bleeding happen? And is the blood raising the pressure inside the skull?

The second question is urgent because the brain sits inside a closed box. The skull cannot accommodate anything extra, so a large volume of blood pushes on normal brain, which can herniate and leave the patient brain dead. In that situation the blood must be removed, by minimally invasive surgery, by drainage procedures or by decompressive surgery. That is the neurosurgeon's role.

Subarachnoid haemorrhage: the two tasks

Subarachnoid haemorrhage is a devastating disease. The typical presenting complaint is a sudden, severe headache; some patients present with seizures or in a coma. Dr. Matin put the share caused by a ruptured intracranial aneurysm at 85%. Aneurysms are either saccular, a rounded berry-like pouch on the side of an artery, or fusiform, a spindle-shaped widening of the whole vessel. When one ruptures, blood spreads into the subarachnoid space, where it shows clearly on a plain CT scan.

Treatment has two aims:

1. Secure the bleeding point. The aneurysm must be closed, because a further bleed would be life-threatening or catastrophic.
2. Prevent vasospasm. In the days after the bleed, the brain's arteries can go into spasm and cut off blood supply. In Dr. Matin's description, vasospasm occurs from day 4 to day 14 in most cases.

In some patients, drains or catheters are also placed to remove the blood, though not in all.

Many patients never reach this stage. The bleed is often so severe that patients are brain dead by the time they arrive at hospital. Those who survive the acute phase and stabilise, as many overseas patients have by the time they travel, still carry an untreated aneurysm that can rupture again at any moment. Dr. Matin describes it as a ticking bomb, and second ruptures are usually massive. Securing the aneurysm is therefore urgent even after the patient has recovered from the first bleed.

Brain aneurysm treatment: clipping vs coiling

Surgical clipping is the more conventional approach. The neurosurgeon opens the skull, dissects through the brain to reach the aneurysm, which often lies in deep structures, and places a clip across its neck. Done well, it is a very efficacious treatment, but it has a long learning curve and carries real risk, because the surgeon must reach deep parts of the brain and clip a fragile vessel without compromising the normal blood supply.

Endovascular coiling reaches the aneurysm from inside the artery. A microcatheter is guided into the aneurysm sac, and coils are deposited inside it. The coils are thrombogenic: blood clots around them, sealing the aneurysm off from the circulation while the parent artery stays open.

The International Subarachnoid Aneurysm Trial (ISAT), published in 2002, randomised 2,143 patients with ruptured aneurysms suitable for either treatment, and found better outcomes with coiling. That trial moved the field towards endovascular treatment.

A basilar tip aneurysm: where coiling is the clear choice

Dr. Matin illustrated the difference with a ruptured aneurysm at the tip of the basilar artery, where it divides into the two posterior cerebral arteries. Reaching this point surgically is extremely difficult. A few very senior surgeons at specialist centres do clip basilar aneurysms, but the surgical route carries significant morbidity. Endovascularly, his team placed coils into the aneurysm, confirmed on three-dimensional imaging that the coil mass filled it, and excluded it from the circulation. In Dr. Matin's experience, the risk of complications during the procedure for such cases is around 3 to 4%.

Treating wide-necked and complex aneurysms

Simple coiling depends on the aneurysm's neck being narrow enough to hold the coils in place. When the neck is wide, or the anatomy is complex, coils can slip out into the parent artery and block normal flow. Dr. Matin described a set of remodelling techniques for these cases.

Balloon-assisted coiling

A small balloon is inflated in the parent artery across the aneurysm's neck while the coils are placed. The balloon protects the neck, so the coils stay inside the sac and do not obstruct normal flow. Once the balloon is deflated and withdrawn, the team checks that the coils are stable, the aneurysm is excluded and the parent artery remains open. Dr. Matin showed this technique in an anterior communicating artery aneurysm, one of the commonest locations for brain aneurysms.

Stent-assisted coiling

Sometimes, when the balloon is removed, the coils threaten to fall back into the parent artery. A stent is then deployed across the neck as a permanent scaffold that holds the coils inside the aneurysm.

Intrasaccular devices

These devices are placed inside the aneurysm sac itself to disrupt flow into it. Dr. Matin's team uses three or four types, and he noted that new devices keep widening the options for complex aneurysms.

Flow diversion

A flow diverter is a densely woven stent placed in the parent artery across the aneurysm's neck. It redirects blood along the artery and away from the aneurysm, which gradually clots and shrinks while the vessel wall heals over the neck. Flow diverters are used for selected wide-necked and fusiform aneurysms that conventional coiling cannot treat well.

What the guidelines say

Dr. Matin summarised the recent American Heart Association and American Stroke Association guidance on aneurysmal subarachnoid haemorrhage:

• Treatment within 24 hours of the onset of the haemorrhage is preferable.
• Complete obliteration of the aneurysm is the goal, to reduce the risk of re-bleeding.
• Where complete obliteration is not possible, partial obliteration to prevent re-bleeding is reasonable.
• For ruptured aneurysms judged suitable for both clipping and coiling, coiling is preferred, and aneurysms of the posterior circulation, such as the basilar artery, are generally treated endovascularly. Flow diverters are considered for selected wide-necked or fusiform aneurysms.

How the choice is made for each patient

At Artemis, the protocol follows the newer guidelines: a patient whose aneurysm suits both treatments is offered coiling as the preferred option. The decision, however, is not forced on the patient. Dr. Matin's team of interventionists and fellows reviews the imaging together, discusses the case with the neurosurgical team, and then holds a multidisciplinary meeting with the family to explain each option, its complexity and its cost. The family decides after that informed discussion; most choose an endovascular procedure. Which endovascular technique is used, plain coiling, stent-assisted coiling or flow diversion, depends on the aneurysm's morphology. Indicative costs for both approaches are on the aneurysm clipping and coiling cost page.

Why brain aneurysms form

No one fully knows, Dr. Matin told the audience. Hypertension is one risk factor, and smoking is a major contributing factor. He explains the mechanism to patients simply. Blood strikes the arterial wall, and either the force is too high, because the blood pressure is raised throughout the body or locally at that point, or the wall has weakened. The weakness can come from an external factor such as tobacco smoke, or from an internal one, such as a genetic weakness of the collagen that forms the wall. Normally the body repairs the damage; when that repair is hindered, the wall bulges out into an aneurysm.

Aneurysms therefore form de novo, over time, through the interplay of these dynamic factors. That distinguishes them from arteriovenous malformations, which are present from birth. An AVM is a developmental condition, and in most patients it is not inherited.

AVM embolisation for lobar bleeds

An arteriovenous malformation (AVM) is an abnormal tangle in which arteries connect directly to veins without the normal capillary bed between them. The high-pressure flow through these fragile vessels can rupture them and cause a bleed.

Dr. Matin showed a patient whose CT revealed blood not in the deep structures, as in a hypertensive bleed, nor in the subarachnoid space, but in the lobes of the brain. Angiography found an AVM lying just beneath the haematoma, with a visible bleeding point. The team went in by catheter and occluded the malformation with a liquid embolic agent that flows like lava and then solidifies, and achieved a complete cure.

Indicative costs for AVM treatment are listed on the AVM treatment cost page.

Recovery after haemorrhagic stroke

Recovery after a bleed follows a different course from recovery after a blocked artery. Dr. Matin frames haemorrhagic stroke as having two aspects: securing the point from which the bleeding happened, and clearing the blood in which the brain is soaked. If both are achieved, the disease is under control.

In a haemorrhagic stroke, the neurons are not completely dead. If they can be brought back, function returns. The first priority, however, is to save the patient's life, because the following week to ten days are life-threatening. Rehabilitation follows. Function then returns over time, depending on how large the bleed was and how severe the disease.

That differs from ischaemic stroke, where the intervention reverses symptoms on the table, as described in the ischaemic stroke article. For patients with a hypertensive bleed, preventing a second one depends on confirming that hypertension was the cause and then controlling the blood pressure aggressively, which reduces the chance of another bleed.

Dr. Matin's answers to the attending doctors on aneurysm risk factors, wide-necked aneurysms and outcomes after haemorrhagic stroke are on the Live Discussion page. Specialists who perform these procedures are listed under neurointervention.