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  1. Symptoms and warning signs
  2. Diagnosis and screening
  3. Living with an unruptured aneurysm
  4. When an aneurysm ruptures
  5. Understanding microsurgical clipping
  6. Coiling and other endovascular options
  7. Understanding flow diversion
  8. Recovery and follow-up
  9. Research and guidelines
On this page

A sudden, severe headache, especially one that reaches its worst within seconds or minutes, needs emergency care. So do sudden weakness, trouble speaking, a seizure or collapse. Call your local emergency number. A headache that eases doesn't rule out bleeding12.

A brain aneurysm, or intracranial aneurysm, is a weak spot in the wall of an artery in the brain that bulges outward. Most are small, round sacs, called saccular or berry aneurysms, at branch points of the arteries at the base of the brain1.

How common it is

About 3% of adults have an unruptured brain aneurysm. A review of 68 studies found a prevalence of 3.2% in adults without other conditions, higher in women and much higher in people with polycystic kidney disease or a family history of aneurysms3. Most are never found and never cause problems.

Rupture risk

Most aneurysms never rupture. In a pooled analysis of 8,382 people with unruptured aneurysms, the average risk of rupture was 1.4% over one year and 3.4% over five years. The risk ranged from 0.25% to more than 15% over five years, depending on age, high blood pressure, a previous bleed, and the aneurysm's size and location4. Smoking and high blood pressure also increase the risk, and growth of an aneurysm on follow-up scans is a warning sign5. See unruptured aneurysms.

When an aneurysm ruptures

A ruptured aneurysm bleeds into the space around the brain, a subarachnoid hemorrhage. The typical symptom is a sudden, extremely severe "thunderclap" headache, often with neck stiffness, vomiting, sensitivity to light, confusion or loss of consciousness2. See symptoms and warning signs.

A subarachnoid hemorrhage is a medical emergency. In population studies, about 35% of patients died in the 1990s, and the figure has stayed around that level since. Of those followed for a year, 45% were living independently6. See ruptured aneurysms.

Treatment

A ruptured aneurysm is treated as soon as possible to prevent a second bleed. For an unruptured aneurysm, the risk of rupture is weighed against the risk of treatment, and many small aneurysms are monitored with repeat scans5. There are three main treatments:

  • Coiling fills the aneurysm with soft platinum coils through a catheter passed up from the groin or wrist. European guidelines recommend it over clipping for a ruptured aneurysm when both are suitable in an adult in good condition7. See coiling.
  • Clipping closes the neck of the aneurysm with a small metal clip, through an opening in the skull. See clipping.
  • Flow diversion places a fine mesh tube in the artery that redirects blood away from the aneurysm, which then closes over months. See flow diversion.

Not the same as an AVM

A brain aneurysm is different from an arteriovenous malformation (AVM), an abnormal tangle of arteries and veins8. It is also different from an aneurysm of the aorta, the main artery in the chest and abdomen.

About the editor

Dr. Kamran Aghayev

Neurosurgeon, Associate Professor of Neurosurgery · Istanbul

Dr. Kamran Aghayev is a neurosurgeon in Istanbul and an associate professor of neurosurgery, with more than 20 years in practice. He trained in neurosurgery at Hacettepe University in Ankara, completed spinal oncology and neuro-oncology fellowships at the H. Lee Moffitt Cancer Center in Tampa, Florida, and taught there as a clinical instructor before returning to Turkey. He chaired the neurosurgery department at Biruni University in Istanbul from 2017 to 2020. His published work includes a surgical technique for jugular vein decompression in atlanto-styloid compression and the PURED operation for thoracic outlet syndrome, and he is a named inventor on 13 U.S. patents for spinal devices.

How this site is editedkamranaghayev.com

References

  1. US National Library of Medicine. MedlinePlus: Brain Aneurysm. Updated 30 September 2024. Source ↩
  2. National Institute for Health and Care Excellence. NG228. Subarachnoid haemorrhage caused by a ruptured aneurysm: diagnosis and management. 2022. Source ↩
  3. Vlak MH, Algra A, Brandenburg R, Rinkel GJ. Prevalence of unruptured intracranial aneurysms, with emphasis on sex, age, comorbidity, country, and time period: a systematic review and meta-analysis. Lancet Neurol. 2011;10(7):626-636. doi:10.1016/S1474-4422(11)70109-0 PubMed ↩
  4. Greving JP, Wermer MJ, Brown RD Jr, et al. Development of the PHASES score for prediction of risk of rupture of intracranial aneurysms: a pooled analysis of six prospective cohort studies. Lancet Neurol. 2014;13(1):59-66. doi:10.1016/S1474-4422(13)70263-1 PubMed ↩
  5. Etminan N et al. European Stroke Journal. 2022;7: LXXXI–CVI. doi:10.1177/23969873221099736. Source ↩
  6. Ziebart A, Dremel J, Hetjens S, et al. Case fatality and functional outcome after spontaneous subarachnoid haemorrhage: a systematic review and meta-analysis of time trends and regional variations in population-based studies. Eur Stroke J. 2024;9(3):555-565. doi:10.1177/23969873241232823 PubMed ↩
  7. Vergouwen MDI et al. European Stroke Journal. 2026;11(5):aakag043. doi:10.1093/esj/aakag043. Source ↩
  8. US National Library of Medicine. MedlinePlus: Arteriovenous Malformations. Webpage. Source ↩

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