The human body has thousands of blood vessels, each responsible for blood flow between the tissues and organs, and the heart. There are three main types of blood vessels - arteries, veins and capillaries.
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Arteries carry oxygen-rich blood under pressure, away from the heart to provide the tissues and organs with oxygen and nutrients
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Veins carry oxygen-depleted blood along with waste and carbon dioxide back to the heart to be reoxygenated
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Capillaries are tiny blood vessels that connect the arteries and veins and exchange carbon dioxide and waste for oxygen and nutrients
Sometimes, a blood vessel can become blocked, causing it to bulge - this is called an aneurysm. An aneurysm can occur in any type of blood vessel, anywhere in the body, but most commonly they occur in the main artery leading away from the heart (the aorta) and the brain.
If this happens to a blood vessel in the brain, it’s called a brain aneurysm. A brain aneurysm MRI scan is helpful in diagnosing this condition, allowing doctors to suggest ways to treat it.
What is a Brain Aneurysm?
A brain aneurysm is caused by a weakness in the wall of a blood vessel in the brain. As blood passes by this weakness, usually where the blood vessels branch off in different directions, blood pressure causes the blood vessel to bulge outwards, causing a brain aneurysm, also known as a cerebral aneurysm or intracranial aneurysm.
Types of Aneurysm
There are two distinct types of cerebral aneurysms - ruptured and unruptured. Rupture means to burst, and if a brain aneurysm bursts, it will cause a subarachnoid haemorrhage and it becomes an urgent medical emergency - the resulting bleeding can lead to potential brain damage if not treated straight away.
Symptoms
A ruptured aneurysm will cause very extreme and immediate symptoms. These include:
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A sudden and intense headache with pain unlike any previous headache
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Nausea or being sick
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Light sensitivity (pain when looking at light or being in a bright room or sunlight)
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Double or blurred vision
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Dilated pupil(s)
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Drooping eyelid(s)
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Neck pain or stiffness
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Dizziness
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Feeling confused or lost
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Unconsciousness
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Seizures (fitting)
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Weakness or numbness in any of the limbs or down one side of the body
A ruptured brain aneurysm is often described as feeling like being hit violently on the head, with “thunderclap” or intense “white light” pain. If you suspect you, a loved one or someone in your vicinity is experiencing a ruptured aneurysm, call 999 immediately.
Unruptured aneurysms on the other hand, don’t always cause any noticeable symptoms, and often go undetected. However, aneurysm size and the location of the aneurysm will have an impact - some particularly large ones will cause some symptoms, as will unruptured intracranial aneurysms that are pressing on the nerves within the brain. Symptoms of an unruptured brain aneurysm include:
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Headaches
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Pain around one or both eyes
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Dilated pupil(s)
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Blurred or double vision
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Slurred or difficult speech
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Weakness or numbness on one side of the face
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Difficulty concentrating
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Short-term memory problems
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Loss of balance
If you’re experiencing any of these symptoms, you should make an appointment to see your GP as soon as possible. Most brain aneurysms will never rupture, but it’s important to have symptoms assessed by a doctor.
If you have a family history of ruptured or unruptured brain aneurysms, you may undergo tests and scans to check your brain and blood vessels. If a scan used to detect brain aneurysms finds that you have an unruptured brain aneurysm, you will have regular brain scans to monitor your situation. There are treatment options that help to reduce the risk that your brain aneurysm ruptures, and we’ll discuss those further on.
Will an Aneurysm Show on an MRI?
Yes, a brain aneurysm, either ruptured or unruptured, will show on an MRI (magnetic resonance imaging) scan of the neck, head and brain.
Can it be Seen on an MRI Without Contrast?
A contrast aneurysm MRI scan is an MRI scan taken with the use of a contrast dye. This dye is injected into a blood vessel, often in the groin, which then travels to the small blood vessels in the brain. The contrast dye helps doctors gain a clearer picture of the health of these blood vessels. Most brain aneurysms can be detected on an MRI scan with or without a contrast dye.
What Does an Aneurysm Look Like on MRI?
An MRI scan shows the outline of all the tissues in the body, including the blood vessels. A blood vessel that’s developed an aneurysm will display bulging - some liken it to a small berry-like image. The scan results will show the aneurysm size, shape and location, and its likelihood of rupturing.
Diagnosing a Brain Aneurysm
There are various steps in the process of getting a diagnosis of brain aneurysm. The processes for diagnosing unruptured and ruptured cerebral aneurysms are very similar, but in the case of a ruptured subarachnoid haemorrhage, the tests will be carried out in an emergency. If imaging tests aren’t completely clear or cannot fully establish a rupture and bleeding, then you may have an additional test called a lumbar puncture. During a lumbar puncture, a small sample of fluid called cerebrospinal fluid (CSF), is taken from your spinal cord. This is then tested for the presence of blood, indicating a subarachnoid haemorrhage.
An unruptured aneurysm is difficult to diagnose as often, there are no symptoms. If you're concerned, or you have a strong family history, then begin by having a chat with your GP. They can refer you for further investigations that will include the following.
Physical Examination
Your GP or specialist will take blood pressure readings, weigh you, and ask you questions regarding your overall health and wellbeing including about your diet and alcohol and smoking history.
Family Medical History Assessment
They will also ask questions about your family, and if you have any known relatives that have or have had a brain aneurysm and if it’s ever ruptured.
Imaging Tests
A brain aneurysm is definitively diagnosed via one or more imaging tests, or scans. There’s a number of scans that can be used:
MRI (Magnetic Resonance Imaging)
An aneurysm MRI scanning machine uses radio waves and magnetic fields to produce detailed images of the brain and the blood vessels that feed it. A trained medic will then be able to assess for signs of aneurysms.
MRA (Magnetic Imaging Angiography)
Magnetic imaging angiography MRA scans are a type of MRI scan used to check the health of the blood vessels and detect brain aneurysms. They utilise radio waves and computer programming to detect blood pooling and clotting in the veins, arteries and capillaries, and subsequent blockages.
CT Scan (Computed Tomography)
A CT scan is another imaging test that can detect brain aneurysms, this time using x rays to provide detailed images. These images are often used to confirm the presence of bleeding in the case of a ruptured brain aneurysm. CT angiography is another type of CT scan using contrast dyes injected into the blood vessels to detect blood flow blockages.
Cerebral Angiography
Cerebral angiography is a procedure used to look for abnormalities in the blood vessels of the brain, including blockages, bulging and bleeding. It involves injecting a dye into the large veins of the groin, allowing it to travel to the brain and then taking x rays of the head and neck to detect changes.
Blood Pressure Monitoring
Blood flow is measured in terms of blood pressure - if your blood pressure is high, it may cause the blood flow through areas of the brain with weakened blood vessels to start to block and bulge - leading to an aneurysm and potentially a rupture. If you’re at risk of a brain aneurysm or a rupture, you may have your blood pressure regularly monitored and you may be given medications to keep it at normal levels.
Genetic Testing
If your family history suggests a genetic predisposition to developing a brain aneurysm or a rupture, you may have genetic counselling and testing to see if you’re at a higher risk. If you are, then you may have an aneurysm MRI scan to assess your level of risk and put a treatment plan in place if necessary.
Causes of an Aneurysm
The reason why some people develop a brain aneurysm while others don’t is still not fully understood. However, doctors and specialists have identified certain risk factors that could mean your chance of developing one are higher. The risk factors for a brain aneurysm include:
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Smoking
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Being overweight or obese
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Eating a diet high in saturated fat and salt
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Having high blood pressure
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Having a history of brain aneurysms in close family members such as a parent or a sibling (these are known as first degree relatives)
Most brain aneurysms are seen in people over 40 years old, and women are more likely than men to develop one. It’s thought this is linked to a loss of oestrogen in women who are experiencing the menopause or who are postmenopausal.
There are several other risk factors that can also slightly increase your risk of developing a brain aneurysm. These include:
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Sustaining a severe head injury that caused damage to the blood vessels
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Being born with a weakness in the blood vessels responsible for blood flow to the neck, head and brain
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Alcohol abuse
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Cocaine abuse
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Having a type of congenital heart disease (heart disease that you’re born with) called coarctation of the aorta that causes a narrowing of the aorta, or the main artery
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Having a genetic kidney condition called autosomal dominant polycystic kidney disease (ADPKD) that causes cysts to form on the kidneys
Prognosis and Treatment
A diagnosis of a brain aneurysm, either ruptured or unruptured can feel frightening and overwhelming. The seriousness of a ruptured brain aneurysm means that it’s important to be aware of the symptoms if you’ve been diagnosed with an aneurysm in the brain, and to have regular monitoring.
It’s estimated that around a quarter of people that experience a ruptured brain aneurysm die within 24 hours. Of those that survive, some will have permanent brain damage, but some will go on to live normal lives with little or no disabilities.
Treatment for a brain aneurysm will depend on the size of the aneurysm, where it is, your age and overall health and wellbeing and whether or not it has ruptured.
If you’ve been diagnosed with an unruptured brain aneurysm, you will be assessed for your risk of it rupturing. Having one or more of the risk factors mentioned in the section above may make your risk higher. But if you’re deemed a low risk of a ruptured brain aneurysm, then you will receive regular check ups, under a process called active observation, to keep a close eye on the situation. If necessary, you may also be given advice on losing weight and giving up smoking, and medications to lower your blood pressure.
There are also certain things you can avoid, in order to reduce your risk of your brain aneurysm rupturing. Try to avoid:
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Being startled
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Getting angry
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Consuming caffeine
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Blowing your nose very hard
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Excessive straining when going to the toilet
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Excessive, high intensity exercise
Those with a higher risk of rupture may be offered surgery. There are two main types of surgery used to prevent a brain aneurysm rupturing:
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Neurosurgical clipping - a neurosurgeon uses a small metal clip to permanently clamp and seal the bulge in the blood vessel, preventing it from bursting.
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Endovascular coiling - during this endovascular treatment, a surgeon places a catheter (a long, thin surgical tube) into a blood vessel in the groin and passes it up into the brain to reach the aneurysm. Small metal coils are passed through the catheter and placed into the affected blood vessel so that blood cannot flow through it, preventing the aneurysm from rupturing.
Both are carried out under a general anaesthetic and which procedure you have will depend on the location, shape and size of the aneurysm.
Treatment for a ruptured aneurysm is much the same - you will undergo neurosurgical clipping or endovascular coiling depending on the nature of your rupture, but with two major differences - surgery will be carried out as an emergency procedure and you will be given a drug called nimodipine that helps to reduce the risk that the flow of blood to your brain will become severely impaired, reducing your risk of brain damage.
Differential Diagnosis
An aneurysm MRI scan can also be used to rule out other conditions such as a stroke, injury to the brain, tumours, multiple sclerosis and infections, that may have similar symptoms.
Why an MRI Scan is a Good Option
Brain magnetic resonance imaging is highly efficient at detecting unruptured aneurysms in the brain that can then be monitored. Since it doesn’t use x rays, there’s no risk of radiation exposure if you undergo regular aneurysm MRI scans to actively observe progress.
How an MRI Scan Detects an Aneurysm
An MRI scan uses radio waves and magnetic fields to manipulate the cells of the body to provide a detailed image of the soft tissues, bones and blood vessels. A trained professional can then use these images along with computer programming and a knowledge of how the blood vessels of the brain should look to confirm or rule out the presence of an aneurysm and its likelihood of rupturing based on its size, shape and location.
Can an MRI Miss an Unruptured Brain Aneurysm?
It’s possible that an aneurysm MRI scan could miss a very small (smaller than 4mm) unruptured brain aneurysm. However, on the whole, an MRI is very effective at detecting aneurysms.
MRI vs CT Scan
An MRI scan tends to be the preferred imaging test to detect unruptured brain aneurysms, whereas a CT scan tends to be used to detect bleeding caused by a ruptured aneurysm, or subarachnoid haemorrhage.
Find an MRI Scan for an Aneurysm
If you or a loved one have symptoms of an unruptured brain aneurysm, then it’s important to speak to a medical professional. Having an aneurysm MRI scan can help to give you peace of mind and treatment if necessary. Book a private MRI scan today. If you’re unsure if an MRI scan is right for you, book an appointment with one of our consultants who can help you decide.
References
Website, N. (2023c, December 4). Brain aneurysm. nhs.uk. https://www.nhs.uk/conditions/brain-aneurysm/
Brain aneurysm - Diagnosis and treatment - Mayo Clinic. (n.d.). https://www.mayoclinic.org/diseases-conditions/brain-aneurysm/diagnosis-treatment/drc-20361595
Macon, B. L. (2021, December 22). What is a brain aneurysm? Healthline. https://www.healthline.com/health/aneurysm-in-the-brain
Brain aneurysm. (2024, September 9). Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/16800-brain-aneurysm
Geng, C. (2023, December 11). Can MRI scans detect a brain aneurysm? https://www.medicalnewstoday.com/articles/brain-aneurysm-mri#accuracy
Brain Aneurysm Foundation. (2024, June 11). MRA vs. MRI - Brain Aneurysm Foundation. https://www.bafound.org/blog/mra-vs-mri/
