A brain aneurysm, also called a cerebral aneurysm, occurs when a blood vessel wall in the brain becomes weakened and a small balloon or bulge forms. If this bulge remains intact, the patient may never experience symptoms. However, if the bulge leaks blood or breaks (ruptures), the condition is a serious and potentially life-threatening medical emergency.


Brain aneurysms occur when the wall of a blood vessel in the brain becomes thin or damaged. This damage may be caused by high blood pressure, atherosclerosis, or rarely after head trauma. In some patients, brain aneurysms occur because of a congenital defect. Although a brain aneurysm can occur in any blood vessel of the brain, they frequently occur in the area between the brain and the thin arachnoid tissue covering the brain, mainly in the base of the skull and in the sylvian fissure (big sulcus contiang the middle cerebral artery)


If a brain aneurysms leaks or ruptures, causing bleeding into the brain, that is known as a subarachnoid hemorrhage and it may be called haemorrhagic stroke. An aneurysm that occurs in the area between the brain and arachnoid tissue layer is called a subarachnoid aneurysm. Other words to describe a cerebral aneurysm help physicians understand its size (small, large, giant, and super-giant) and shape.

  • Saccular aneurysms form a sack-like pouch protruding from the vessel wall.
  • Berry aneurysms are saccular aneurysms with a neck that resembles a plant stem.
  • Fusiform aneurysms are bulges in the artery wall and have no necks.


If a brain aneurysm forms but does not leak or rupture, the patient may have no symptoms. In some cases, an aneurysm may cause symptoms by putting pressure on nearby brain tissue or nerves. In such cases, a patient may report:

  • Pain above or behind one eye
  • Dilated pupil
  • Visual disturbance or double vision
  • Numbness, weakness, or paralysis of one side of the face
  • Drooping eyelid
  • Epileptic fit

In some cases, an aneurysm will start to leak blood into the brain before it breaks. This is sometimes called a sentinel bleed because it alerts clinicians to the likelihood of a dangerous rupture. Symptoms of a leaking aneurysm include a very severe headache that comes on suddenly.

A leaking aneurysm often progresses to a ruptured aneurysm. However, some aneurysms rupture without first producing a sentinel bleed. The most common signs of a ruptured cerebral aneurysm are:

  • Sudden-onset, extremely severe headache
  • Nausea and vomiting
  • Stiff neck
  • Visual impairment or double vision
  • Extreme sensitivity to light
  • Seizure
  • Drooping eyelid
  • Loss of consciousness
  • Confusion
  • In severe cases death may occur


Cerebral aneurysms are very serious medical conditions that are fatal in some patients. Those who recover may have neurological deficits. However, some patients with cerebral aneurysm make a full recovery with little or no neurological problems afterward. The patient’s chances for full recovery depend on many factors including how soon the patient got expert treatment, the patient’s age and overall health, and the severity of his symptoms before the treatment, and location of the aneurysm.

Risk Factors

Some known risk factors for cerebral aneurysm are things that cannot be helped: individuals who are older, female, or have a family history of aneurysm are thought to be at higher risk for brain aneurysms. Other risk factors include:

  • Smoking
  • Hypertension (high blood pressure)
  • Atherosclerosis (hardening of the arteries)
  • Abuse of illicit drugs, especially cocaine
  • Alcohol abuse
  • Head trauma
  • Certain blood infections


Cerebral aneurysms are potentially life-threatening medical emergencies which usually cause abrupt symptoms, including a sudden severe headache. New surgical and technological approaches are improving outcomes, but such innovations depend on expert care and treatment in a highly specialised setting.