Brain aneurysm

A brain aneurysm (AN-yoo-riz-um) 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 (hemorrhagic stroke). Most often a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain. This type of hemorrhagic stroke is called a subarachnoid hemorrhage.

A ruptured aneurysm quickly becomes life-threatening and requires prompt medical treatment.

Most brain aneurysms, however, don't rupture, create health problems or cause symptoms. Such aneurysms are often detected during tests for other conditions.

Treatment for an unruptured brain aneurysm may be appropriate in some cases and may prevent a rupture in the future.

Symptoms Causes Risk factors Complications

Ruptured aneurysm

A sudden, severe headache is the key symptom of a ruptured aneurysm. This headache is often described as the "worst headache" ever experienced.

Common signs and symptoms of a ruptured aneurysm include:

  • Sudden, extremely severe headache
  • Nausea and vomiting
  • Stiff neck
  • Blurred or double vision
  • Sensitivity to light
  • Seizure
  • A drooping eyelid
  • Loss of consciousness
  • Confusion

'Leaking' aneurysm

In some cases, an aneurysm may leak a slight amount of blood. This leaking (sentinel bleed) may cause only a:

  • Sudden, extremely severe headache

A more severe rupture almost always follows leaking.

Unruptured aneurysm

An unruptured brain aneurysm may produce no symptoms, particularly if it's small. However, a large unruptured aneurysm may press on brain tissues and nerves, possibly causing:

  • Pain above and behind an eye
  • A dilated pupil
  • Change in vision or double vision
  • Numbness, weakness or paralysis of one side of the face
  • A drooping eyelid

Seek immediate medical attention if you develop a:

  • Sudden, extremely severe headache

If you're with someone who complains of a sudden, severe headache or who loses consciousness or has a seizure, call 911 or your local emergency number.

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