A brain aneurysm often causes no problem, but can be life-threatening, if it ruptures.

In July 2020, Grant Imahara, host of popular TV series MythBusters, suffered a brain aneurysm that led to his death. A brain or cerebral aneurysm refers to a bulge or ballooning in an artery in the brain. Some of us may be walking around with a brain aneurysm without realising it.

“It is estimated that three out of 100 people may be harbouring such aneurysms, and they are often only discovered when brain scans are done for other reasons,” said Dr Wickly Lee, Senior Consultant, Department of Neuroradiology, National Neuroscience Institute (NNI).

When discovered incidentally, most aneurysms are small (less than 5mm). They are unlikely to cause symptoms but they still require follow-up and surveillance to ensure the aneurysm has no other sinister features that increase the risk of rupture, said Dr Lee. However, approximately 10 of 3,000 aneurysms do rupture and require emergency treatment, as the resulting bleeding in the brain can be fatal.

Assessing risks

Brain aneurysms can occur in anyone and at any age, but are more common in people aged 40 to 60 years old, according to Dr Vincent Ng, Senior Consultant, Department of Neurosurgery, NNI. Known risk factors include smoking, high blood pressure, and a family history of aneurysm.

<<Left: ​Dr Vincent Ng; right: Dr Wickly Lee>>

Some patients with genetic disorders that cause weakening of the blood vessel walls or have other health conditions, such as polycystic kidney disease, may have a predisposition to the formation of aneurysm, said Dr Ng.

Diagnosis is done via a Magnetic Resonance Imaging (MRI) scan or a Computerised Tomography (CT) scan. However, making the decision to treat an unruptured aneurysm can be complex.

“All brain procedures carry a risk of serious complications, therefore we need to carefully weigh this against the risk of an aneurysm rupturing,” said Dr Ng. “We will assess the patient’s risk factors and look at the size and shape of the aneurysm — the more irregular it is, the more likely it will rupture.”

Clinicians also consider the patient’s age, blood pressure, location of the aneurysm, and its growth over time.

As a large majority of aneurysms are small, doctors prefer to take a conservative approach, and monitor the size and shape of the aneurysm annually with MRI or CT scans.

“If follow-up scans show that the size or shape of the aneurysm has changed, or if the patient presents initially with a 5mm or larger aneurysm, we will recommend treatment,” said Dr Lee.

Did you know aneurysms can develop in other parts of the body? Find out more here.

Presence of symptoms

Symptoms typically do not occur unless an aneurysm is large or ruptures. One of the most obvious signs is intense headache, which is often described as the “worst headache of your life”. This may be accompanied by nausea, vomiting, and sensitivity to light.

The trigger for ruptured aneurysms is possibly associated with stressful activity or vigorous exercises, such as gym workouts or heavyweight lifting, said Dr Ng.

“But sometimes the patients could also be doing something very innocuous and the aneurysm just ruptures,” he added.

A ruptured aneurysm is a medical emergency and requires urgent treatment. There are two ways this can be done:

• Endovascular embolisation

This is a minimally invasive procedure performed under image guidance. Treatment of the aneurysm is performed from “within” the artery through a thin catheter, which is inserted via a groin artery and carefully navigated to the brain aneurysm. Materials such as tiny coils or mesh stents can then be deployed to promote clotting of the aneurysm.

• Surgical clipping

This requires open brain surgery to place a small metal clip around the aneurysm neck, preventing blood from entering it.

“When a rupture happens, there is a 30 to 40 per cent probability of immediate death, and the situation becomes significantly more acute. Follow-up treatments are highly recommended, as an aneurysm can rupture again within a short time. The second occurrence carries a higher death rate of 70 per cent,” said Dr Ng.

Technological aid

Traditionally applied in fields like aerodynamics and weather simulation, an engineering tool called Computational Fluid Dynamics (CFD) uses data to analyse problems that involves fluid flows. This tool is being adapted in the medical field to predict the risk of brain aneurysm rupture using parameters such as arterial blood flow pattern, wall shear stress, and vorticity (rate of fluid rotation). It is still in the research stage, but it is hoped that this technology can provide additional data to help clinicians like Dr Ng and Dr Lee assess the likelihood of a brain aneurysm rupturing in the future.

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