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Author: Jenny Tao


A brain aneurysm is a bulge or ballooning in a blood vessel in the brain. It often looks like a berry hanging on a stem.

A brain aneurysm can leak or rupture, causing bleeding into the brain. (This is a type of hemorrhage stroke.)

Brain aneurysms are more common in adults than in children and more common in women than in men.

credit: Mayo Clinic



Ruptured brain aneurysms

  • Sudden and severe headache, often described as “the worst headache of my life”

  • Nausea/vomiting

  • Stiff neck

  • Blurred or double vision

  • Sensitivity to light

  • Seizure

  • Drooping eyelid

  • A dilated pupil

  • Pain above and behind the eye

  • Loss of consciousness

  • Confusion

  • Weakness and/or numbness

Unruptured brain aneurysms

  • Blurred or double vision

  • A drooping eyelid

  • A dilated pupil

  • Pain above and behind one eye

  • Weakness and/or numbness

‘Leaking’ aneurysms (In some cases, an aneurysm may leak a slight amount of blood.)

  • Sudden, extremely severe headache

A more severe rupture often follows leaking.



The causes of a brain aneurysm are currently unknown.


Risk Factors

Risk factors that develop over time

  • Older age

  • Cigarette smoking

  • High blood pressure (hypertension)

  • Drug abuse, particularly the use of cocaine

  • Heavy alcohol consumption

  • Some types of aneurysms may occur after a head injury (dissecting aneurysm) or from certain blood infections (mycotic aneurysm).

Risk factors present at birth

  • Inherited connective tissue disorders, such as Ehlers-Danlos syndrome, that weaken blood vessels

  • Polycystic kidney disease, an inherited disorder that results in fluid-filled sacs in the kidneys and usually increases blood pressure

  • Abnormally narrow aorta (coarctation of the aorta), the large blood vessel that delivers oxygen-rich blood from the heart to the body

  • Cerebral arteriovenous malformation (brain AVM), an abnormal connection between arteries and veins in the brain that interrupts the normal flow of blood between them

  • Family history of brain aneurysm, particularly a first-degree relative, such as a parent, brother, sister, or child


Complications that develop after the rupture

  • Re-bleeding. 

  • Vasospasm. After a brain aneurysm ruptures, blood vessels in your brain may narrow erratically (vasospasm). This condition can limit blood flow to brain cells (ischemic stroke) and cause additional cell damage and loss.

  • Hydrocephalus. Bleeding in the space between the brain and surrounding tissue (subarachnoid hemorrhage) — most often the case — can block the circulation of the fluid surrounding the brain and spinal cord (cerebrospinal fluid). This condition can result in an excess of cerebrospinal fluid that increases pressure on the brain and can damage tissues (hydrocephalus).

  • Hyponatremia. Subarachnoid hemorrhage from a ruptured brain aneurysm can disrupt the balance of sodium in the blood. This may occur from damage to the hypothalamus, an area near the base of the brain. A drop in blood-sodium levels (hyponatremia) can lead to swelling of brain cells and permanent damage.



  • Surgical clipping

  • Surgical coiling


Treatment for aneurysm is difficult due to problems accessing parts of the brain, and may only be considered if the aneurysm is considered to be at risk of rupturing or has ruptured already.


Useful links



“Statistics and Facts.” Brain Aneurysm Foundation, 17 Nov. 2020, 

 “Brain Aneurysm.” Headway, 

“Brain Aneurysm.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 9 Aug. 2019, 

“Warning Signs/Symptoms.” Brain Aneurysm Foundation, 17 Feb. 2021, 

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