Brain Aneurysm (Aneurysm in the Brain): Risks, Diagnosis, and Modern Treatment

A cerebral aneurysm is also known as a cerebral vascular dilation, an arterial dilation in the brain, or an arterial bulge in the brain. It is a spindle-shaped, berry-shaped, or sac-shaped dilation of the brain’s arterial vessels.

The cerebral aneurysm has a diameter of approximately 5 mm to 3 cm. If the aneurysm measures 2.5 cm or more, it is classified as a giant aneurysm. Aneurysms in the brain occur most frequently in the vessels at the base of the brain. Due to the structure of the vessel wall, the branching points of the arteries are most commonly affected.

Illustration of a cerebral aneurysm © freshidea | AdobeStock

A serious complication of a cerebral aneurysm is aneurysm rupture, meaning the aneurysm bursts or tears open. Since a ruptured cerebral aneurysm can quickly become life-threatening, immediate treatment is required. A cerebral aneurysm can rupture at any age. However, the risk of a cerebral aneurysm rupturing is highest in the fifth and sixth decades of life.

15 to 20% of aneurysm patients have more than one cerebral aneurysm. In about 10 to 20% of cases, multiple aneurysms are present in the arteries of the brain base. According to estimates, between 0.2% and 9% of Central Europeans have an aneurysm. This means that approximately 2,000 to 90,000 people per 1 million have a cerebral aneurysm. Women are affected more frequently than men.

A cerebral aneurysm develops as a result of changes in the endothelial cells lining the inside of blood vessels. Often, the exact cause of a cerebral aneurysm cannot be clearly determined. Cerebral aneurysms run in some families. Therefore, it is believed that not only acquired but also congenital factors contribute to these vascular changes.

As a result, over the years and in the presence of other factors—such as

• cerebral vascular occlusion,
• high blood pressure

a cerebral aneurysm may develop.

The muscle layer surrounding the cerebral arteries at the base of the brain is thinner than that of other arteries in the body. As a result, the cerebral arteries at the base of the brain are particularly susceptible to cerebral aneurysms.

A major risk factor for a cerebral aneurysm is high blood pressure (hypertension). In this condition, the blood exerts high pressure on the inside of the vessel walls. If the vessel wall is weakened at a specific point, that area can give way, and the weakened spot bulges outward like a sac. This is how a cerebral aneurysm develops. Atherosclerosis (hardening of the arteries) is another risk factor for a cerebral aneurysm. Calcium deposits cause the cerebral arteries to lose their elasticity, making it harder for the vessels to cushion the pressure waves caused by the heartbeat.

High blood pressure is a risk factor for the formation of a cerebral aneurysm © wutzkoh | AdobeStock

Other risk factors for a cerebral aneurysm include

• smoking,
• advanced age,
• heavy alcohol consumption,
• head injuries, and
• certain genetic disorders (e.g., Marfan syndrome, Ehlers-Danlos syndrome).

A brain aneurysm often causes no symptoms at first.

However, if the dilated blood vessel presses on a cranial nerve, symptoms may develop. Unlike peripheral nerves, cranial nerves do not originate from the spinal cord but emerge directly from the brain.

As a result, paralysis and sensory deficits in the facial region are common. If the aneurysm ruptures, it leads to a cerebral hemorrhage or a stroke.

Symptoms of an Unruptured Cerebral Aneurysm

In most cases, the facial nerve (nervus oculomotorius) is affected by the cerebral aneurysm. The facial nerve is responsible for eye movements. Therefore, pressure on the nerve from the cerebral aneurysm can lead, among other things, to

• eye movement disorders,
• paralysis of the eye muscles,
• pain above and behind an eye,
• dilated pupils,
• double vision,
• drooping eyelid, and even
• paralysis of one side of the face

.

Such symptoms can usually be alleviated by brain aneurysm surgery.

Symptoms of a Ruptured Brain Aneurysm

A brain aneurysm at the base of the brain is very dangerous. If an aneurysm in a large blood vessel at the base of the brain ruptures, it can lead to bleeding into the subarachnoid space. This is referred to as an aneurysmal subarachnoid hemorrhage (SAH). The subarachnoid space is the space between the brain and the arachnoid membrane.

Subarachnoid hemorrhage occurs in about 100 people per 1 million inhabitants each year. Because the blood cannot drain outward due to the bony skull, pressure on the brain increases. This can lead to severe brain damage. Up to 60 to 70% (some sources even report up to 90%) of patients do not survive the brain hemorrhage.

Only about 10% of patients with a ruptured brain aneurysm are left without any neurological deficits. The remaining patients experience neurological deficits, such as

• loss of speech,
• complete or partial paralysis (paresis), or
• hemiparesis.

Symptoms attributable to increased intracranial pressure may include

• sudden-onset, very severe headaches,
• nausea and vomiting,
• stiff neck,
• drowsiness,
• sensitivity to light,
• drowsiness,
• Loss of consciousness, and
• coma

. If a brain aneurysm ruptures, immediate surgery is necessary.

A brain aneurysm does not necessarily cause symptoms. It is therefore often discovered incidentally as an incidental finding during a computed tomography (CT) or magnetic resonance imaging (MRI) scan of the head. If the brain aneurysm has ruptured, a presumptive diagnosis can often be made based on the symptoms (e.g., sudden onset of headache).

If a cerebral aneurysm is suspected, imaging techniques are helpful. They can clearly visualize a ruptured cerebral aneurysm and a cerebral hemorrhage. Additional diagnostic tests include a cerebrospinal fluid (CSF) analysis and cerebral angiography. A computed tomography (CT) scan is usually the first diagnostic step. A contrast agent may be used if necessary. This X-ray examination allows for clear visualization of blood flow in the brain. Cerebral hemorrhages and a ruptured cerebral aneurysm are also easily detectable with this method.

Magnetic resonance imaging (MRI) usually provides more detailed information about the hemorrhage and cerebral vasodilation than a CT scan. Furthermore, it does not involve the use of X-rays. In the case of a subarachnoid hemorrhage, red blood cells can be detected by examining the cerebrospinal fluid (CSF). A cerebrospinal fluid (CSF) analysis is usually performed when a CT scan shows no evidence of bleeding, but the symptoms suggest it. During this procedure, a small amount of CSF is extracted from the spinal canal using a needle as part of a lumbar puncture.

If these tests do not provide definitive results, a cerebral angiography may be performed. For this procedure, a thin, flexible catheter is advanced through a large artery—usually from the groin—into the brain. A contrast dye is used to highlight the cerebral arteries. A ruptured aneurysm can then be clearly visualized on a CT scan.

A screening test for an unruptured brain aneurysm is particularly recommended if

• a parent or sibling has had a ruptured brain aneurysm, or
• if there is a congenital condition that increases the risk of cerebral aneurysm.

Not every brain aneurysm discovered incidentally poses a risk. If the brain aneurysm causes no symptoms and the vessel walls are stable, treatment is often not necessary. In such cases, regular follow-up examinations are sufficient.

However, if there is a risk of aneurysm rupture, the vessel must be treated preventively. The weakened area is reinforced, or the brain aneurysm is clipped. A risk exists, for example, in cases of a family history of the condition and certain risk factors.

The clip used in clipping is a metal clip that the surgeon places at the base of the cerebral aneurysm. This does not narrow the lumen of the vessel. Alternatively, small platinum coils can be inserted via a minimally invasive, endovascular procedure (coiling).

Other neurosurgical approaches to treating cerebral aneurysms include:

• wrapping: The weakened areas of the vessel are wrapped with the patient’s own tissue or foreign material to reinforce them
• Trapping: Small balloons are inserted upstream and downstream of the cerebral aneurysm.

Acute secondary bleeding from a ruptured cerebral aneurysm is the cause of the high mortality rate within the first few days after rupture. The most important goal in all cases of aneurysmal cerebral hemorrhage is therefore to stop the bleeding as quickly as possible and to occlude the source of the bleeding.

Early surgery (0 to 3 days after the subarachnoid hemorrhage) generally yields better long-term outcomes than late surgery (11 to 14 days after the subarachnoid hemorrhage). The poorest outcomes are expected with surgery performed between the 7th and 10th day after the subarachnoid hemorrhage. Even today, patients with severe symptoms or persistent unconsciousness are often not operated on until their condition has stabilized.

Depending on

• age,
• general condition, and
• location, size, and shape of the cerebral aneurysm

, treatment is generally either endovascular or neurosurgical.

Endovascular brain aneurysm surgery (endovascular coiling, endovascular aneurysm occlusion)

In endovascular brain aneurysm surgery, a hollow microcatheter is advanced from the groin into the affected cerebral artery. The surgeon then inserts a stent. A stent is a fine wire mesh that reinforces the vessel wall from the inside.

Using a guidewire, microspirals made of a platinum alloy (coils) are then inserted into the aneurysm sac. Although these coils only partially fill the cerebral aneurysm, they promote the formation of a thrombus. In this way, they prevent further blood flow into the aneurysm and a potential rupture.

This brain aneurysm procedure requires neither a neurosurgical opening of the skull nor surgery on the brain itself. Therefore, this minimally invasive brain aneurysm procedure is the preferred technique. If there are no complications, the coil material remains permanently in the brain and does not need to be removed.

Tiny coils partially fill the brain aneurysm (coiling) © Naeblys | AdobeStock

If coiling is not possible or if a brain aneurysm has ruptured (emergency treatment), a different method is necessary. A neurosurgeon then opens the skull. Three techniques are possible:

• Clipping
• Wrapping
• Trapping

Neurosurgical Brain Aneurysm Surgery: Clipping

In clipping, the neck of the aneurysm is completely clamped off with a clip (usually made of titanium). This isolates the aneurysm sac from the bloodstream. The cerebral artery on which the aneurysm is located remains intact.

If the clip is not positioned optimally, there is a risk that

• a new cerebral aneurysm may form or
• stenosis (narrowing) of the parent vessel may occur.

In some cases, a follow-up angiography is therefore performed after surgery. If there are no complications, the clip remains permanently in the brain and does not need to be removed.

During clipping, the aneurysm is clamped off © ilusmedical | AdobeStock

Neurosurgical Brain Aneurysm Surgery: Wrapping

In wrapping, the surgeon wraps the arterial wall of the cerebral aneurysm. Wrapping can be performed using the patient’s own tissue (e.g., muscle or fascia) or with foreign material (e.g., gauze, linen, or plastic). The resulting connective tissue reinforcement of the wall is intended to prevent rupture.

However, the cerebral aneurysm remains intact during wrapping. It may even increase in size, which is why the protective effect of this cerebral aneurysm surgery is controversial.

Neurosurgical Brain Aneurysm Surgery: Trapping

The term “trapping” is used when the surgeon clamps a blood vessel above and below the cerebral aneurysm using

• clips or
• endovascular balloons

.

This procedure can only be performed if the area of the brain supplied by the affected cerebral artery has an alternative blood supply. For this reason, comprehensive cerebral perfusion and functional tests are required prior to brain aneurysm surgery.

Postoperative Care Following a Cerebral Aneurysm Surgery

After neurosurgical or endovascular brain aneurysm surgery, the patient must be closely monitored. This allows any complications to be detected and treated in a timely manner.

Treatment of Symptoms and Complications

In addition to direct surgical treatment of the cerebral aneurysm, symptoms and complications are usually managed with medication. For example, the patient may be prescribed

• pain relievers for headaches and
• calcium channel blockers to prevent vasospasm. Vasospasm refers to a narrowing of the intracranial arteries, which can lead to severe cerebral infarcts with fatal consequences.

The disturbance in cerebrospinal fluid circulation, which is detectable on a CT scan just a few hours after the hemorrhage, is treated with lumbar drainage or ventricular drainage.

Patients with an unruptured cerebral aneurysm can reduce the risk of rupture. The most important factor is a healthy lifestyle:

• Avoid smoking and drugs.
• Maintain a healthy, balanced diet and get enough exercise. Changing your diet and engaging in physical activity can help lower your blood pressure.
• Limit your caffeine intake. Caffeine can cause a sudden spike in blood pressure.
• Avoid overexertion. Sudden and intense physical exertion (e.g., weightlifting) can lead to a sudden spike in blood pressure.
• Be cautious when taking acetylsalicylic acid (aspirin) and other medications that inhibit blood clotting. Discuss this with your doctor, as these medications increase the risk of bleeding in the event of a brain aneurysm.

What is a brain aneurysm?

A brain aneurysm is a bulge in a blood vessel or cerebral artery in the brain. This sac- or berry-shaped change is caused by a weakening of the vessel wall. Brain aneurysms are among the most common vascular disorders in the skull. A brain aneurysm is a bulge that can pose varying degrees of danger depending on its size and location.

What symptoms does a brain aneurysm cause?

An unruptured aneurysm often causes no symptoms and goes unnoticed for a long time. If symptoms do occur, they may include headaches, visual disturbances, or neurological deficits. If the aneurysm ruptures, it usually leads to severe headaches and acute cerebral hemorrhage. A rupture is a medical emergency.

What risk factors contribute to the development of a brain aneurysm?

The most important risk factors include high blood pressure, smoking, genetic predisposition, and advancing age. Various factors contribute to the development of a cerebral aneurysm and increase the risk of subsequent rupture. Studies on risk factors for intracranial aneurysms also show that a family history of the condition can play an important role. Women sometimes have a higher risk of cerebral aneurysms than men.

How is a brain aneurysm diagnosed?

The diagnosis is usually made using MRI, CT, or magnetic resonance imaging with contrast dye. This allows for the visualization of aneurysms, their location within the blood vessel, and any possible changes in the vessel wall. In specialized centers, additional neuroradiological procedures are also used. Many brain aneurysms are discovered by chance before symptoms appear.

How is a brain aneurysm treated?

Treatment of a brain aneurysm depends on its size, location, and individual risk. In coiling, a catheter is inserted through the groin and guided into the brain aneurysm, where it is filled with fine platinum coils. This causes the blood inside the aneurysm to clot, reducing the risk of rupture. In clipping, a neurosurgeon closes off the aneurysm directly at the affected site. Both treatment options can significantly reduce the risk of serious complications.