About Hereditary Brain Aneurysms

What is a hereditary brain aneurysm?

In most cases, brain aneurysms are not hereditary, and there is generally only a single case in a family. Occasionally, however, an individual with a brain aneurysm will have other close family members who have also had brain aneurysms.

When two or more first-degree relatives (parent, child, or sibling) have proven brain aneurysms, people can be given the diagnosis of ‘familial aneurysm syndrome’ and close family members may be referred for further investigations and screenings. In the medical community, these are often referred to as familial aneurysms. 

Screenings for people who may be at risk

In the UK, the NHS currently recommends that people who may be at risk from familial brain aneurysm syndrome speak to their GP, who can then refer them to a specialist clinic.

Screenings are currently recommended for people who have had two or more first-degree relatives (father, mother, sister or brother) experience a brain aneurysm or a ‘subarachnoid haemorrhage’ caused by one.

NHS England currently recommended that clinical screening is only available to people thought to have a significant risk of having a brain aneurysm that could rupture at some point in the future.

Further NHS information and advice can be found on the NHS website

How many people are affected by brain aneurysms?

It's difficult to estimate exactly how many people are affected by brain aneurysms because they usually cause no symptoms and remain undetected throughout life.

Our recently published Targeted Literature Review showed that according to a 2005 study, there are 7,221 cases of ruptured brain aneurysms in the UK each year.

However, as the review highlights, the UK population has grown by 8 million people since 2005 and so there is a need for more data regarding the number of brain aneurysms in the UK. It is also impossible to tell how many of these have a hereditary pattern or are sporadic, meaning they happen suddenly and without a family history.

More information can be found on our research page.

Who is affected?

Current NHS guidance states that brain aneurysms can develop in anyone at any age but are more common in people over the age of 40, and women tend to be affected more commonly than men.

Most aneurysms happen without any family history. This is often down to ‘bad luck’ although sometimes environmental factors, such as smoking, high blood pressure and excess alcohol can play a part.

A history of aneurysms in a family also increases the risk, with cases of unruptured brain aneurysms higher in individuals with a strong family history of brain aneurysms. If brain aneurysms are proven to run in families, the condition is known as ‘familial intracranial aneurysms ‘(FIA) and individuals are often diagnosed with familial aneurysms syndrome (FAS).

Our Targeted Literature Review highlights some of the many studies that look into the genetic causes of hereditary brain aneurysms. Our report highlights the most common variants that have been identified in global research. More needs to be done to improve our understanding of the genetic causes. We hope that by working with the research community we can increase our knowledge of what the genetic factors may be, and improve the diagnosis and treatment journey for families.

My family has been impacted by an aneurysm, what are the risks to me?

Just like heart attacks, ruptures or aneurysm haemorrhages (where an aneurysm bursts) are usually one-off events in someone's life and usually don’t carry a hereditary risk. Sometimes though, patterns occur in families. When this happens, further investigation is needed.

If you have a strong family history, meaning more than two or more first-degree relatives have been impacted by the condition, there is a 2.3% to 29.4% chance of having an unruptured brain aneurysm compared with 0.2% - 8.8% of the general population. There are many statistics out there and you will find different numbers in different places. At the moment there is no one number that defines increased risk. Visit our research page for more information.

Current advice from the NHS says that aneurysm screening with an imaging study of the brain vascular system (i.e. MRI scan) is recommended for people who have two or more first-degree relatives (father, mother, sister or brother) who have experienced a subarachnoid haemorrhage (where an aneurysm has burst and there is bleeding in the space between your brain and the surrounding membrane) or have a confirmed diagnosis.

It is important to note that screening is a personal choice. Some people who are offered screening choose not to know due to the increased worry and anxiety it may bring. Often talking about your risks with specialists and genetic counsellors can help you understand the risks and make an informed choice for yourself.

What happens if an aneurysm is found?

If an aneurysm is found, the specialist - usually a neurosurgeon or a neurovascular specialist - will work with you to determine if the aneurysm should be treated and, if so, what type of treatment to have. Sometimes the specialist may suggest a ‘watch and wait’ approach, depending on the size and location of the aneurysm. That means you’ll undergo regular screening to monitor its size. If no aneurysm is detected, a repeat screening may be recommended in the future. This is all dependent on your family history, your desire to be screened and willingness to know, and on the advice of your clinician. Not everyone wants to undergo screening and that is a personal and valid choice. It is always up to the individual to decide what’s best for them.

For more information on treatment options, please visit the NHS website.

What’s the latest NHS advice if I think that I may be at risk from a hereditary brain aneurysm?

There is limited information and guidance on the NHS website about familial disease.  For information including details about how brain aneurysms are diagnosed and treated please follow this link. If you have a strong family history, including two or more first-degree relatives, members of your close family (parents, brothers, and sisters) may also be advised to have an MRA or MRI scan to check for possible aneurysms too.

If you have any questions or concerns, talk to your GP about your family history and your worries. They can then advise on the next steps and how to access NHS screening. You may also be referred to a genetic counsellor to talk through your family history and decide whether screening is right for you. More information about genetic testing is also available on the NHS website.

NHS Lothian has produced a useful guide for people who are considering screening for brain aneurysms. To download a pdf of the guide visit this link: information for adults considering screening for brain aneurysm.pdf (nhslothian.scot)

I’ve been diagnosed with a hereditary brain aneurysm, what are my options?

Although everyone's journey will be different, there are a number of options open to you. You can discuss the best options for you with your specialist or neurosurgeon. For more information on treatment options, please visit the NHS website: Brain aneurysm - Treatment - NHS (www.nhs.uk)

If you are worried and would like to talk through your concerns with a trained specialist, the Brain & Spine Foundation Helpline nurses can help you by talking through your questions and providing explanations on anything you don’t fully understand. They are there to help and can be contacted on 0808 808 1000.

    I'm feeling worried, who can help?

    The Brain & Spine Foundation is a great place to get support and information, helping you to tackle concerns and help inform your choices and plans. The information and support available includes:



    If you are worried, you could contact your GP who can talk you through options and may refer you to a genetic counsellor (a specialist in hereditary conditions).


    For more immediate support, you can talk to a trained specialist at the Brain & Spine Foundation. Their Helpline nurses can help you by talking through your questions and providing explanations on anything you don’t fully understand. They are there to help and can be contacted on 0808 808 1000.

    Speak to Brain & Spine Foundation

    What genetic research is available?

    Within the ‘Targeted Literature Review’ (a look at the research available on this condition) published by HBA Support in 2022 a review and summary of current genetic research shows there are multiple genetic candidates that cause hereditary brain aneurysms. However, there is currently no consensus and insufficient understanding of theses in the clinical community. More research is needed to help build the list of genetic candidates and understand their significance. It is hoped that eventually, genetic screening (a simple blood test) would allow early diagnosis of those at risk so that preventative measures can be taken.

    In February 2021, NICE also concluded, through its review of treatment, that more research is needed in this important area. The NICE report explored routes to diagnosing and treating an aneurysmal (caused by a ruptured aneurysm) subarachnoid haemorrhage and its complications and provides recommendations to improve the speed and accuracy of diagnosis and ensure that the most effective treatments are offered.

    Where can I get support for a non-familial brain aneurysm?

    For immediate support on brain aneurysms and brain haemorrhages, you can talk to a trained specialist at the Brain & Spine Foundation. Their Helpline nurses can help you by talking through your questions and providing explanations on anything you don’t fully understand. They are there to help and can be contacted on 0808 808 1000.

    Where can I go for further information?

    The organisations below also offer help and information on brain aneurysms and brain injuries. For any concerns or worries, please always speak to your GP or a clinical professional.

    What are the latest guidelines from NICE?

    The latest advice from NICE covers diagnosing and treating an aneurysmal (caused by a ruptured aneurysm) subarachnoid haemorrhage (where an aneurysm has burst and there is bleeding in the space between your brain and the surrounding membrane) and its complications. It provides recommendations to improve the speed and accuracy of diagnosis and ensure that the most effective treatments are offered, together with guidance on follow-up care and information for people (aged 16 and over) who have had an aneurysmal subarachnoid haemorrhage, their families and carers.  Within the latest draft guide, the authors also recommended that additional research was needed to look into familial risk and advice for families.

    More information and the draft guidelines can be found on the NICE website.

    Frequently Asked Questions

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