brain aneurysm is a bulge in a blood vessel in the brain. It is caused by a weakness in the blood vessel wall, where it is usually situated. A brain aneurysm can leak or rupture, causing bleeding into the brain (hemorrhagic stroke). If this happens, immediate medical treatment is required, as ruptured aneurysms are life-threatening. Most brain aneurysms, however, don't rupture, create health problems or cause symptoms. Such aneurysms are often detected during medical examinations for other conditions.


Most brain aneurysms will only cause noticeable symptoms if they burst (rupture). Such symptoms of a ruptured aneurysm may include:

  • Throbbing headache
  • Nausea and vomiting
  • Neck pain
  • Blurred or double vision
  • Pain on looking at light
  • Seizure
  • Sagging eyelids
  • Faint spells
  • Confusion

An unruptured brain aneurysm may produce no symptoms, however it may press on brain tissues and nerves most likely causing:  

  • Sharp pain above and behind the eye
  • Enlarged pupil
  • Blurred or double vision
  • Numbness, weakness or paralysis of one side of the face
  • Sagging eyelid


Brain aneurysms are most likely to develop as a result of thinning artery walls. Aneurysms are most common and often form at the branches in arteries because those areas of the blood vessel are weaker.

Risk factors 

There are many factors that can contribute to weakness in an artery wall and increase the risk of a brain aneurysm. Identified risk factors include:

  • Smoking
  • High blood pressure
  • Old age
  • Drug abuse
  • Head wound
  • Alcohol abuse
  • Certain blood infections

Risk factors present at birth include:

  • A family history of brain aneurysms
  • Inherited connective tissue disorders such as Ehler’s Danlos syndrome
  • Abnormally narrow aorta (the large blood vessel that delivers oxygen rich blood from the heart to the body)
  • Cerebral arteriovenous malformation (Brain AVM)


Complications that may develop after the rupture of an aneurysm include:

  • Re-bleeding: An aneurysm that has ruptured or leaked is at risk of bleeding again. Re-bleeding can cause further damage to brain cells.
  • Vasospasm: A condition in which a blood vessel’s spasm leads to vasoconstriction. This condition can limit blood flow to brain cells and cause damage or loss of cells.
  • Hydrocephalus: A build-up of fluid (cerebrospinal fluid) deep within the brain that can cause damage to it by increasing pressure and damaging tissues. 
  • Hyponatremia: A medical condition where the level of sodium in the blood is too low and can cause damage to the hypothalamus, an area near the base of the brain.


The most efficient ways to prevent brain aneurysms or reduce the risk of an aneurysm growing and possibly rupturing is to avoid actions that may damage the blood vessels. These include:

  • Smoking
  • Eating fatty foods
  • Not exercising regularly
  • Obesity