What are the symptoms of a brain aneurysm?

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

Watch this video to learn more from Dr. Mehmet Oz about symptoms of aneurysms.

There are generally no symptoms of cerebral aneurysm, until or unless they rupture. They then cause a severe headache that comes on immediately, as if one were being “shot in the head.” Ruptured aneurysms cause death in 50% of cases. Sometimes there are “low volume bleeds” with similar headaches that go away quickly, but they often precede a catastrophic bleed. This is why someone with the abrupt onset of a severe headache should always be evaluated immediately in an emergency room.

Aneurysms are abnormal parts of blood vessels where the wall of the vessel becomes weak and the vessel balloons outward. Most brain aneurysms do not cause any symptoms, unless they burst and cause subarachnoid hemorrhage, which causes sudden and severe headache and may cause confusion, sleepiness, and other neurological signs such as weakness. In some cases, unruptured aneurysms may cause symptoms, due to pressure of the aneurysm on surrounding nerves or brain tissue. Symptoms may include headache, loss of vision, abnormalities in eye movements, weakness, and facial pain. 

Brain aneurysms most frequently present for medical attention because they bleed, causing vague, non-specific symptoms such as headaches, visual problems, slowed mental processes, balance problems, etc. The majority of aneurysms that rupture do so without any preliminary signs or symptoms. Some effects that occur upon rupture are:

  • Onset of a "thunderclap" (sudden, extremely painful) headache
  • Stiff neck
  • Intolerance of bright light
  • Nausea and/or vomiting
  • Seizures
  • Sudden weakness
  • Loss of consciousness

If you experience a sudden and severe headache, seek immediate medical attention, as it possibly may signal SAH as the cause.

In about 20 percent of aneurysms that go on to rupture, a "warning leak" occurs several days before subarachnoid hemorrhage. In these patients, the warning headache may be much milder than the thunderclap. Small strokes or seizures also may occur.

Unruptured aneurysms can press on adjacent brain structures such as cranial nerves and cause symptoms such as cranial nerve palsy, dilated pupils, double vision and pain above and behind the eye.

Brain aneurysms usually won't show signs or symptoms before they hemorrhage. Sometimes, though, an aneurysm may press on surround brain structures, causing headache, numbness, pain behind the eye, vision change, and weakness. Doctors can determine if these symptoms and warning signs are related to a cerebral aneurysm, often by using imaging tests such as computed tomography (CT) and magnetic resonance imaging (MRI) scans. Brain angiograms may also be used for treatment planning.

Symptoms vary depending on the nature of the aneurysm. Small aneurysms that do not grow or rupture typically produce no symptoms. Aneurysms that are growing may put pressure on brain tissue or surrounding nerves. This may result in pain behind or above the eyes, dilated pupils, a drooping eyelid, changes in vision, numbness, or even face paralysis. Once an aneurysm ruptures, the result is a very painful headache. The pain is sudden and severe. Nausea and vomiting may occur. The person may lose consciousness. Double vision, neck stiffness, light sensitivity, and confusion also are possible symptoms.

Most cerebral aneurysms do not show symptoms until they either become very large or burst. Small, unchanging aneurysms, generally will not produce symptoms, whereas a larger aneurysm may press on tissues and nerves. Symptoms may include pain above and behind the eye; numbness, weakness, or paralysis on one side of the face; dilated pupils; and vision changes. When an aneurysm hemorrhages, an individual may experience a sudden and extremely severe headache, double vision, nausea, vomiting, stiff neck, and/or loss of consciousness. Individuals usually describe the headache as "the worst headache of my life" and it is different in severity and intensity from other headaches that people may experience. "Sentinel" or warning headaches may result from an aneurysm that leaks for days or weeks prior to rupture. Only a minority of individuals have a sentinel headache prior to aneurysm rupture.

A brain aneurysm is an emergency, so it's critical to know the signs. In this video, stroke neurologist Dr. Carolyn Brockington describes the symptoms that should make you reach out for immediate medical help.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.