Intracranial aneurysm

A cerebral aneurysm is an abnormal widening of an artery in the brain caused by weakness of the blood vessel wall. This increases the risk of rupture and can lead to life-threatening hemorrhage. The prevalence of cerebral aneurysms is estimated to be between 1.5 and 8%, although most do not show symptoms until they become large or rupture.

Intracranial aneurysms are relatively common and, for the most part, do not create health problems and cause no symptoms. As a result, many are never diagnosed and may be detected during tests performed for other conditions.

Their exact causes are unknown, but important risk factors that may contribute to their development have been identified. These include:

  • Advanced age.
  • Smoking.
  • Hypertension.
  • Drug abuse.
  • Excessive alcohol consumption.
  • Sex, being more frequent in women.
  • Traumatic brain injuries.
  • Certain infections by microorganisms.

In addition, although much less frequently, aneurysms may be related to certain pathologies such as connective tissue disorders (eg Ehlers-Danlos syndrome), polycystic kidney disease or congenital arteriovenous malformations.

Intracranial aneurysm is a protrusion or dilatation of a cerebral blood vessel that is potentially dangerous because of the risk of hemorrhage. Among the studies carried out, an association study involving approximately 11,000 cases and more than 300,000 controls shows 16 loci significantly associated with the condition. Among the genes identified, most have known or putative roles in blood vessel function and blood pressure regulation. This study highlights the polygenic nature of the disease and would explain, according to the authors, 21.6% of the genetic basis.


In most cases, intracranial aneurysms are asymptomatic, especially when they are small. However, when they are large they can exert pressure on the tissues and may cause pain, dilated pupil, changes in vision or numbness on one side of the face.

Occasionally, intracranial aneurysms rupture, causing more severe symptoms that may include:

  • Sudden and very intense headache.
  • Nausea and vomiting.
  • Neck stiffness.
  • Blurred vision and sensitivity to light.
  • Convulsions.
  • Pale skin.
  • Loss of consciousness.

In these cases immediate medical treatment is required.


Prevention of intracranial aneurysms involves controlling risk factors, especially in older people and those with a family history of the disease. Among them, special care should be taken in cardiovascular risk factors and diseases that can weaken blood vessels, such as diabetes, hypercholesterolemia and atherosclerosis. In addition, a healthy lifestyle should be maintained, avoiding stress and the consumption of tobacco and alcohol.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

16 loci


Bakker MK, van der Spek RAA, van Rheenen W, et al. Genome-wide association study of intracranial aneurysms identifies 17 risk loci and genetic overlap with clinical risk factors. Nature Genetics. 2020 Dec;52(12):1303-1313.

UK National Health Service (NHS) [March 2022]

Tawk RG, Hasan TF, D'Souza CE, Peel JB, Freeman WD. Diagnosis and Treatment of Unruptured Intracranial Aneurysms and Aneurysmal Subarachnoid Hemorrhage. Mayo Clin Proc. 2021 Jul;96(7):1970-2000.

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