What is a Brain Aneurysm?


A brain aneurysm, also known as a cerebral aneurysm, is a bulging in a blood vessel of the brain. The blood flowing in the brain puts pressure on this weakened area of the vessel causing the formation of a bulge.1 A brain aneurysm can be a life-threatening condition. The most serious complication of a cerebral aneurysm is a rupture, which results in bleeding in the brain.2 The causes of a brain aneurysm are not fully understood but they will be discussed in this article along with the symptoms and management of the condition. 

Causes of a brain aneurysm

Although the exact causes of cerebral aneurysms are not yet known, there are several risk factors that may increase the risk of a cerebral aneurysm or a rupture. These risk factors include:1,3-6

  •  Smoking
  • High blood pressure
  •  Drug use (especially cocaine)
  • Alcohol
  • Older age
  • Being assigned female at birth (AFAB) 
  • Other medical conditions (e.g., connective tissue disorders, polycystic kidney disease, brain arteriovenous malformation)
  •  Genetic cause (family history of the condition)
  • Severe head injury

Signs and symptoms of a brain aneurysm

If a brain aneurysm ruptures, it causes bleeding in the brain which can result in a stroke or even death. Therefore, knowing the signs and symptoms of a brain aneurysm is important for seeking medical attention and treatment immediately. The majority of brain aneurysms do not rupture, especially if they are small aneurysms. However, if a rupture occurs, it can cause severe a headache. Signs and symptoms of a ruptured brain aneurysm include:3,6,7

  • Severe headache
  • Stiff neck 
  • Blurred vision
  • Drooping eyelid
  • Light sensitivity
  • Loss of consciousness
  • Confusion
  • Nausea
  • Vomiting
  • Subarachnoid hemorrhage (SAH) (bleeding in the area between the brain and the tissue that covers the brain)
  • Hemorrhagic stroke (bleeding in the brain and skull)

More permanent complications caused by brain aneurysms include:6,7

  • Seizures 
  • Coma (prolonged unconsciousness) 
  • Hydrocephalus (increased pressure in the brain due to buildup of cerebrospinal fluid or blood)
  • Vasospasm (blood vessels get thinner and not much oxygen reaches the brain)
  • Death (half of the ruptured aneurysm cases result in death)

There are some cases in which the aneurysm is not completely ruptured but there is a small amount of blood leakage. In these cases, people experience a severe headache that lasts up to two weeks.3,6

If an aneurysm is small and not leaking, it may not show any signs or symptoms. Nevertheless, a brain aneurysm that is larger but unruptured can cause:3,6

  • Numbness at one side of the individual’s face
  • Dilated pupils
  • Blurred or double vision
  • Pain behind or above one of the individual’s eye

Management and treatment for brain aneurysm

Depending on the circumstances and severity, ​an unruptured brain aneurysm may not need treatment. Ruptured brain aneurysms should be treated by reducing the blood flowing into the aneurysm. The two main surgical techniques used to prevent ruptures or further damage are neurosurgical clipping and endovascular coiling.3,6,7

In neurosurgical clipping, the surgeon cuts a small opening in the skull to access the aneurysm and shut it. The surgeon has to locate the blood vessel that caused the aneurysm and place a metal clip to stop the blood from flowing into the aneurysm using small instruments and a microscope. This technique can be very effective, and the recurrence of the aneurysm is rare. If necessary, another procedure may be carried out in combination with clipping, called a bypass. This procedure aims to divert the blood flow around the clipped area by using a blood vessel taken from another part of the body. The patient needs 4 to 6 weeks to fully recover from this surgery depending on whether the aneurysm was ruptured or not. Nevertheless, the risks of this procedure are loss of brain blood flow or excessive bleeding in the brain.3,6,7

Endovascular coiling is a less invasive procedure and involves the placement of a catheter (tube) into an artery in the groin or wrist which later reaches the aneurysm area. Then, coils or stents may be placed in the aneurysm preventing the blood from flowing into it. The coil causes the clotting of the blood eventually leading to the destruction of the aneurysm. A stent may be inserted with the coil to hold the coil in place. These two techniques discussed may be used to treat unruptured aneurysms as well, however, the potential risks of the surgery may outweigh the benefits.3,6,7

A new endovascular technique used for treating especially large brain aneurysms is flow diversion. In this procedure, the neurosurgeon places a stent (flow diverter) to divert the flow of blood away from the aneurysm. This reduces the risk of aneurysm rupture since less blood flows into the aneurysm. Overall, the neurosurgeon will work with your healthcare team to decide the best treatment for you.3,6,7


How is a brain aneurysm diagnosed?

The majority of people who have an unruptured aneurysm do not even know they have one. A healthcare specialist is able to detect the aneurysm using imaging tests. These tests will show if the aneurysm has ruptured and whether there is bleeding in the adjacent areas of the brain. These tests may include:1,3,6,7

How can I prevent a brain aneurysm?

Brain aneurysms cannot always be prevented, but their risk can be lowered by reducing your blood pressure and avoiding smoking. Smoking cessation can significantly decrease the risk of brain aneurysm development. Blood pressure can be maintained within a healthy range via medications and lifestyle habits such as a healthy diet. A healthy diet that helps in reducing your blood pressure includes low amounts of salts, alcohol, caffeine, and plenty of fruits and vegetables. Additionally, it is important to maintain a healthy weight and exercise regularly.6,7

Who is at risk of a brain aneurysm?

Several factors increase the risk of developing a brain aneurysm such as smoking, being AFAB, old age, family history, drugs, and other medical conditions. Many people may have unruptured aneurysms that may not cause any symptoms. If they rupture, however, certain factors can affect the outcome. These factors include:3

  • Location and size of the aneurysm
  • Age
  • Sex assigned at birth 
  • The amount of bleeding
  • The time before getting medical help
  • The occurrence of other medical conditions

How common is a brain aneurysm?

Brain aneurysms affect 3% to 5% of the general population.1,2 It is hard to estimate exactly how many people are affected since brain aneurysms usually do not show any symptoms unless they become ruptured. Despite this, in the UK there are 1 in 15,000 ruptured brain aneurysms each year.6

When should I see a doctor?

Screening for unruptured aneurysms using imaging tests is not recommended unless you are at high risk. This means having a family history of cerebral aneurysms or a disorder that increases the risk of having a cerebral aneurysm. If you have an unruptured aneurysm, your doctor should monitor its size regularly as well as risk factors such as high blood pressure. If you have had a ruptured aneurysm, you should visit your healthcare team regularly to make sure you do not develop another aneurysm.7


A brain aneurysm is a life-threatening condition that can have severe complications such as brain damage, stroke, or even death. They can be caused by several factors including high blood pressure, smoking, other medical conditions, drugs, alcohol, and family history. The most common symptoms include a severe headache, neck pain, blurred vision, and sensitivity to light. The two most common treatment options are endovascular coiling and neurosurgical clipping. It is crucial to seek medical attention if you are at a high risk of developing a brain aneurysm or if you are experiencing any symptoms. 


  1. Brisman JL, Song JK, Newell DW. Cerebral Aneurysms. The New England Journal of Medicine; 2006. 355: 928-939.
  2. Chalouhi N, Hoh BL, Hasan D. Review of cerebral aneurysm formation, growth, and rupture. Stoke; 2013. 44: 3613-3622.
  3. Mayo Clinic. 2023. Brain Aneurysm. https://www.mayoclinic.org/diseases-conditions/brain-aneurysm/symptoms-causes/syc-20361483
  4. Vlak MHM, Algra A, Brandenburg R, Rinkel GJE. Prevalence of unruptured intracranial aneurysms, with emphasis on sex, age, comorbidity, country, and time period: a systematic review and meta-analysis. The Lancet Neurology; 2011. 10: 626-636. 
  5. Chalouhi N, Ali MS, Starke RM, Jabbour PM, Tjoumakaris SI, Gonzales F, Rosenwasser RH, Koch WJ, Dumont AS. Cigarette smoke and inflammation: role in cerebral aneurysm formation and rupture. Mediators of Inflammation; 2012. Article ID: 271582.
  6. National Health Service (NHS). 2023. Brain Aneurysm. https://www.nhs.uk/conditions/brain-aneurysm/causes/
  7. Cleveland Clinic. 2023. Brain Aneurysm. https://my.clevelandclinic.org/health/diseases/16800-brain-aneurysm
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

Get our health newsletter

Get daily health and wellness advice from our medical team.
Your privacy is important to us. Any information you provide to this website may be placed by us on our servers. If you do not agree do not provide the information.

Athina Servi

Research Assistant at Imperial College London, Department of Brain Sciences

My name is Athina Servi, and I am a young professional with a strong academic background
and a passion for neuroscience and mental health. I graduated from the University College
London with a degree in Biomedical Sciences BSc and then I pursued a Translational
Neuroscience MSc at Imperial College London where I currently work as a Research
Assistant. My academic and professional journey so far has provided me with extensive
experience in various healthcare settings. I believe in making medical information accessible
to everyone, not just those with a medical background. Through my writing, I want to help
people better understand their health, make informed decisions about their care, and
ultimately, live healthier, happier lives. I hope you enjoy my article!

my.klarity.health presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
Klarity / Managed Self Ltd
Alum House
5 Alum Chine Road
Westbourne Bournemouth BH4 8DT
VAT Number: 362 5758 74
Company Number: 10696687

Phone Number:

 +44 20 3239 9818