An introduction to brain aneurysms
A guest article I wrote and illustrated for Brainbook; the original is available on their neurosurgery public engagement blog.
An aneurysm is a bulge in the wall of an artery. It creates a weak point in a pressurised system. The aneurysm can burst, leaking blood with catastrophic results, including disability and death. There is an important network of arteries in the brain called the circle of Willis (shown in red). These supply the brain with nutrient and oxygen filled blood, needed to keep us alive. This network is particularly vulnerable to developing aneurysms.
If a brain aneurysm bursts, the resulting bleeding is known as a subarachnoid haemorrhage, which just describes the anatomical layer the bleed happens within. The blood supply to the area of brain this artery supplies is then compromised, causing a stroke, which impairs the functions which that brain tissue is responsible for, e.g. speech, or sight.
Brain aneurysm rupture (bursting), and the resulting subarachnoid haemorrhage (bleeding around the brain), is therefore extremely serious. Permanent disability, or death can happen quickly if it is not managed promptly.
That sounds less than ideal. Can anything be done?
I’m glad I asked. Yes, there is actually; thanks to the discipline of neurosurgery. The management options will depend on two major factors:
- Whether the aneurysm has already ruptured
- How medically fit a patient is for major surgery
Option #1: Clipping
The skull is opened up, the aneurysm is found, and then ‘clipped’ with a metal clip. This cuts off the blood flow within the aneurysm, sealing it off from the arterial circulation. It will then wither over time. It can be really technically challenging for neurosurgeons to reach a brain aneurysm. They must operate tools in a confined space with limited visibility, and successfully clip it without cutting off blood flow to the brain.
Option #2 - coiling
Our second option is more suited to patients who cannot undergo a major surgery. With ‘coiling’, the surgeon will insert a small catheter (tube) into an artery in the groin, and snake this through the arterial circulation into the aneurysm using imaging guidance. Once here, a thin metal wire is pushed into the aneurysm, where is ‘coils’ into a messy ball. This is left here, and the catheter removed. The metal coil agitates the blood, triggering a clot to form around itself, which effectively seals the aneurysm off from the circulation.
Okay, great. But who actually gets aneurysms?
More people than you might think.. Experts estimate between 1 in 20 and 1 in 100 people has a brain aneurysm. They are most common in African-Americans, then Hispanics, and lastly White individuals. Women get them more commonly than men, by a factor of 3:2. Smoking and high blood pressure are modifiable risk factors. Rupture is most common in those over 40 years of age.
Don’t worry too quickly however; although rupture can be fatal, this only occurs in 1 in 12,500 aneurysms. The risk increases greatly if a previous aneurysm has ruptured. Knowing this helps inform decisions to treat before another ruptures.
What do you feel when a brain aneurysm ruptures?
The symptoms of an aneurysm bursting are largely the result of a sub arachnoid haemorrhage, which is a bleed (haemorrhage), under (sub), the arachnoid layer of the brains coverings. A person will experience a sudden, severe headache, sometimes called a ‘thunderclap headache’. This has been described as ‘feeling like you were hit across the head with a baseball bat'. It is not a vague, mild headache, that came on gradually. 15% of people who get a subarachnoid haemorrhage are dead before reaching hospital.
Other symptoms of rupture are those of ‘meningism’ which is irritation of the meninges, (the protective layers of tissue which cover the brain), or symptoms of raised intracranial (within the skull) pressure, and include:
- Photophobia: eye pain caused by bright light
- Blurred vision: vision that is blurry, as in not clear, as in.. I think you get it.
- Neck stiffness: moving the head is painful. Looking down, or touching the chin to the chest is particularly limited by pain
- Reduced level of consciousness
Brain aneurysms can be scary, life threatening problems. There are limited things a person can do to prevent their occurrence or rupture, and they need to be dealt with immediately if they burst. Fortunately, there are some clever things neurosurgeons can do to stop, and prevent aneurysm rupture when caught in time.
Article written and illustrated by Dr Ciléin Kearns (artibiotics). The content has been additionally reviewed by Mr Alex Alamri, Neurosurgery Specialty Trainee at Barts Health Trust, a co-founder of Brainbook. See Brainbook’s neurosurgeons in action on their YouTube channel.