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Around 4-8 in 100 people with ADPKD have a small aneurysm: a ‘ballooning out’ of a blood vessel due to weakness in the vessel wall. Aneurysms may occur in the blood vessels of the brain (when they are called intracranial aneurysms, ICA or ‘berry aneurysms’).

Aneurysms affect a minority of people with ADPKD, but they are one of the most important complications because they may cause the blood vessel to burst. In the brain, this leads to a type of stroke called a subarachnoid haemorrhage. (The bleeding or haemorrhage occurs in the arteries underneath a membrane in the brain called the arachnoid, which lies just below the surface of the skull.)

Brain aneurysms rarely burst. But people with ADPKD with a brain aneurysm have a higher risk of subarachnoid haemorrhage than people without ADPKD who also have a brain aneurysm, especially if other family members have been affected. Subarachnoid haemorrhage also tends to occur at a younger age in people with ADPKD.

A subarachnoid haemorrhage can be life threatening, so screening is recommended for people with ADPKD and a family history of brain aneurysms. It is possible to treat brain aneurysms with surgery to prevent them from bursting, but this can itself be risky. So surgery is usually recommended only if its risks are less than the risks of a burst aneurysm.

Causes of brain aneurysms

The ADPKD genes PKD1 and PKD2 are now known to play a role in maintaining the structure of blood vessels. So this may explain why brain aneurysms affect several members of ADPKD families with certain genetic mutations.

However, non-inherited factors can also increase the risk of brain aneurysms in anyone:

  • Smoking is an important risk factor, possibly because substances in tobacco smoke damage the walls of the blood vessels.
  • High blood pressure increases the likelihood of a brain aneurysm by raising the pressure on the walls of the blood vessels.
  • Cocaine, which raises blood pressure and causes inflammation inside the walls of the blood vessels.

Symptoms of brain aneurysms

Less than half of people with a brain aneurysm have any symptoms. Symptoms occur when the aneurysm increases in size or presses against other structures inside the brain.

Seek the immediate advice of a doctor if you or a relative has:

  • Headaches
  • Loss of vision
  • Weakness
  • Difficulty speaking
  • Facial pain
  • Seizures or fits.

If a brain aneurysm bursts, the bleeding will cause sudden symptoms. Telephone for an ambulance immediately if you or a relative has:

  • Severe, sudden and extremely painful headache (the worst you have ever had)
  • Sensitivity to light
  • Stiff neck
  • Feeling or being sick
  • Mental confusion
  • Blurred or double vision
  • Slurred speech
  • Paralysis
  • Loss of consciousness.

Diagnosing brain aneurysms

A brain aneurysm can be diagnosed using:

  • Magnetic resonance angiography (MRA): this is the most effective test. MRA does not use X-rays. Instead, a dye is injected in to the bloodstream and highlights the blood vessels in the brain. Any bulges in vessel walls can be seen on the image produced by the machine. MRA uses a powerful magnetic field and you need keep still with your head inside the machine. So, you will not be able to have an MRA if you have a pacemaker or other metal objects in your body, or if you have claustrophobia.
  • CT scanning: this is an alternative to MRA, but it involves a large dose of X-rays and is not as accurate.
  • Carotid angiography—direct injection of a dye into the arteries in the neck (carotid arteries)—is used if doctors suspect that a brain aneurysm has burst. It is not used to identify an aneurysm that has not burst, because it has a high rate of complications.

Treating brain aneurysms

Treatment depends on your own health, the size and position of the aneurysm, and the likelihood that it will burst:

  • ‘Watchful waiting’ (regular screening with MRA to monitor the size of the aneurysm) is recommended for small aneurysms that cause no symptoms and are unlikely to burst.
  • Neurosurgical clipping uses a titanium clip or clamp across the neck of aneurysm. This means that a small opening will be made in your skull while you are unconscious under general anaesthetic.
  • Endovascular coiling or embolisation involves a small tube or micro-catheter that is passed through an artery in your leg to reach the aneurysm in the brain via the blood vessels. Once the aneurysm is full of coils, an electrical charge is used to cut the end of the coils from the micro-catheter, which is then withdrawn. Within the aneurysm, blood clots around the coils to prevent it from rupturing. Coiling is a less serious operation than clipping and seems to be safer, but it cannot be used if the aneurysm cannot be reached through a catheter.

Preventing brain aneurysms

A healthy lifestyle is the best way to reduce the likelihood that you will develop a brain aneurysm, or that a brain aneurysm will burst:

If you have an aneurysm, your doctor will also advise how you can reduce the risk that it will burst. But generally, you should avoid:

  • Activities that force the muscles to contract for a long time, e.g. lifting heavy weights, prolonged labour during childbirth.
  • Contact sports, e.g. rugby

Screening for brain aneurysms

At present screening for brain aneurysms is not routinely recommended for everyone with ADPKD. Screening is only recommended for people with ADPKD:

  • Who are known to have or are suspected of having a brain aneurysm: the frequency of screening depends on the size, position and any changes in the aneurysm
  • Who have a family history of brain aneurysms, but do not themselves have an aneurysm: screening is recommended every five years

Learn more from PKD Charity

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Authors and contributors

With thanks to all those affected by ADPKD who contributed to this publication.


Disclaimer:  This information is primarily for people in the UK. We have made every effort to ensure that the information we provide is correct and up to date. However, it is not a substitute for professional medical advice or a medical examination. We do not promote or recommend any treatment. We do not accept liability for any errors or omissions. Medical information, the law and government regulations change rapidly, so always consult your GP, pharmacist or other medical professional if you have any concerns or before starting any new treatment.

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If you don't have access to a printer and would like a printed version of this information sheet, or any other PKD Charity information, call the PKD Charity Helpline on 0300 111 1234 (weekdays, 9am-5pm) or email 

The PKD Charity Helpline offers confidential support and information to anyone affected by PKD, including family, friends, carers, newly diagnosed or those who have lived with the condition for many years.