Cerebral Aneurysm


What is a cerebral aneurysm?

A cerebral (in the brain) aneurysm (AN-yoo-riz-um) is a bulge or ballooning in a blood vessel in the brain. The bulge often occurs at a weak place in the inner muscular layer of the vessel’s wall. It can leak blood or break open and cause bleeding into the brain, producing a hemorrhagic stroke. Most aneurysms don’t rupture or cause symptoms. However, if it breaks, this is a life-threatening medical emergency. Treatment of an unruptured aneurysm may prevent a future rupture and stroke. 

The reason that aneurysms develop, grow and rupture is not known. Certain risk factors make them more likely to rupture. Aneurysms most commonly develop at the base of the brain just inside the skull, called the subarachnoid space. If they rupture in this location it can cause a subarachnoid hemorrhage and stroke. Aneurysms can range in size from an eighth of an inch in diameter to an inch. If they’re larger than an inch, they can be very dangerous and hard to treat.  

Why should I worry about a cerebral aneurysm?

Because a ruptured aneurysm can cause a stroke, permanent brain damage, physical disability and even death. You have a 20% chance of having one or more aneurysms after the first aneurysm.


What causes a cerebral aneurysm?

The cause is unknown, but several factors can increase your risk of developing an aneurysm, including:

  • Age older than 40 years
  • Female 
  • High blood pressure -- the constant pressure from blood circulation puts extra pressure at points where the arteries branch off (like a balloon that becomes weaker as it stretches, an enlarging aneurysm becomes weaker, increasing the risk of rupture)
  • Smoking tobacco
  • Infections
  • Direct trauma to the brain from an injury or fall
  • Heavy alcohol use
  • Long-term or heavy use of drugs like cocaine or amphetamines
  • Other blood vessel disorders (fibromuscular dysplasia, cerebral arteritis or arterial dissection), although these are rare 

What causes an aneurysm to rupture?

The direct cause of a rupture or leak is unknown. Your risk increases with these behaviors:

  • High blood pressure that not controlled
  • Strong emotions from anger or being upset can raise blood pressure
  • Heavy lifting or straining can increase pressure in the brain 
  • Taking blood thinners or prescription drugs that act as stimulants
  • Cocaine use

Some inherited (present at birth) risk factors include:

  • Connective tissue disorders that weaken blood vessels
  • Polycystic kidney disease that increases blood pressure
  • Abnormally narrow aorta (coarctation of the aorta), the large blood vessel in the heart that delivers oxygen to the body
  • Abnormal connection between arteries and veins in the brain
  • Family history of brain aneurysm

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What are the symptoms of cerebral aneurysm?

Unruptured aneurysms may not cause any symptoms. In approximately half of unruptured aneurysms, the patient may have:

  • Headaches
  • Pain behind one eye and a dilated pupil
  • Seizures
  • Change in vision or double vision
  • Weakness
  • Face pain or numbness on one side of the face

Leaking aneurysm may cause a sudden and very severe headache that can last for hours to days. A severe rupture usually follows leaking. 

Ruptured aneurysm can cause a stroke, called subarachnoid hemorrhage. The bleeding causes damage to or kills surrounding cells, and increases pressure inside the skull. Skull pressure can disrupt blood and oxygen to the brain, causing loss of consciousness or death. 

Other symptoms include:

  • Sudden, extremely severe headache
  • Nausea and vomiting
  • Stiff neck
  • Blurred or double vision
  • Sensitivity to light
  • Trouble speaking or understanding what’s being said
  • Seizure or loss of consciousness
  • Increasing skull pressure disrupts blood and oxygen to the brain
  • Drooping eyelid
  • Weakness or paralysis of an arm or leg
  • Drowsiness or loss of consciousness
  • Confusion
  • Coma

Several complications can occur after an aneurysm ruptures, including:

  • Rebleeding after a leak or rupture can further damage brain cells. Once it leaks blood, the chances are very high that the aneurysm will leak again. The risk of rupturing also increases.
  • Vasospasm, a narrowing of the brain’s blood vessels, limits blood flow to brain cells and can cause an ischemic stroke.
  • Hydrocephalus (increased pressure on the brain) can be caused by bleeding in the space between the brain and surrounding tissue, blocking circulation of the fluid surrounding the brain and spinal cord.
  • Hyponatremia (a drop in blood-sodium levels) can lead to swelling of brain cells and brain damage.


How is a cerebral aneurysm diagnosed?

Several tests are used to diagnose cerebral aneurysms:

  • Diagnostic cerebral angiogram uses contrast dye injected into a blood vessel in the groin to check for blood vessel aneurysms in the brain. It is used when other tests don’t provide enough information. This test also provides information to develop a therapy plan.
  • Computed tomographic angiography uses a contrast dye injected into a vein to check for aneurysms. 
  • Magnetic resonance angiography takes images of the brain’s blood vessels. 
  • Spinal tap (lumbar puncture) draws brain/spine fluid to check it for blood cells.


Are there treatments for cerebral aneurysm?

Ruptured aneurysms can be treated with procedures that all have the same goal: to eliminate blood from flowing into the aneurysm. Treatment for ruptured aneurysms includes:

  • Surgical clipping closes off the aneurysm by placing a tiny metal clip on the neck of the aneurysm to stop blood flowing into it. The neurosurgeon must remove a small section of skull to reach the aneurysm. This is a technically difficult procedure that carries a very slightly higher probability of death or dependency/disability, compared to endovascular coiling.  
  • Endovascular coiling is less invasive. It does not require opening the skull, providing lower risk of infection. It takes less time so there’s less time under anesthesia. The risk of needing to repeat the procedure is higher for this method. At one year after the procedure, patients treated with the coiling method had a better chance of disability-free survival, compared to the surgical clipping method. The procedure uses a catheter inserted into an artery and threaded through to the aneurysm. A soft wire is inserted through the catheter into the aneurysm where it coils up inside, disrupting the blood flow. This procedure seals off the aneurysm from the artery. The procedure must be repeated if the aneurysm reopens. 
  • Flow diverters are a new treatment procedure. These stent-like implants divert blood away from the aneurysm. Stopping blood flow helps the body reconstruct the artery and heal the area. This method is especially helpful with large aneurysms that can’t be treated with other methods. 

The most serious complication of any of these treatments is a ruptured aneurysm. Rupture can cause a massive hemorrhage, hemorrhagic stroke, bleeding into the brain, coma or death. Reported rupture rates are only 2% to 3% for either procedure. Surgical clipping provides a better chance to control massive bleeding because the neurosurgeon has direct access to the ruptured aneurysm and can more quickly control bleeding. 

Unruptured aneurysms may or may not be treated. This remains a matter of debate among neurosurgeons. Treatment depends on size and location of the aneurysm, age and health of the patient, congenital conditions, and family history of ruptured aneurysms. Most unruptured aneurysms should be treated according to these guidelines:

  • Small (less than 5 mm in diameter) aneurysms should be managed conservatively with monitoring
  • Medium (larger than 5 mm) aneurysms in patients younger than age 60 should be considered for treatment
  • Large (larger than 10 mm) aneurysms should be treated in nearly all patients younger than age 70

If treatment is deemed safe and necessary, these methods may be used:

  • Surgical clipping is often the best treatment for unruptured aneurysms, even though it’s an invasive and technically difficult procedure. 
  • Medical therapy can lower the risk of rupture. It includes controlling blood pressure, and stopping smoking and recreational drugs like cocaine and amphetamines. Blood pressure medication, a healthier diet and more exercise will help control blood pressure.  
  • Periodic monitoring of the aneurysm with imaging scans (CT, MRI or angiography) will be done to track its growth.


Mayo Clinic. (Aug. 2019). Brain aneurysm. Retrieved 11-5-2021, {https://www.mayoclinic.org/diseases-conditions/brain-aneurysm/symptoms-causes/syc-20361483}
Mayo Clinic. (Aug. 2019). Brain aneurysm Diagnosis and Treatment. Retrieved 11-5-2021, {https://www.mayoclinic.org/diseases-conditions/brain-aneurysm/diagnosis-treatment/drc-20361595}
American Association of Neurological Surgeons. (N.d.). Cerebral Aneurysm. Retrieved 11-5-2-2021, {https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Cerebral-Aneurysm/}
American Stroke Association. (Dec. 2018). What You Should Know About Cerebral Aneurysms. Retrieved 11-5-21, {https://www.stroke.org/en/about-stroke/types-of-stroke/hemorrhagic-strokes-bleeds/what-you-should-know-about-cerebral-aneurysms}


Medically reviewed by:

Dr. Desiree Levyim

Dr. Desiree Levyim is a board eligible neurologist in practice since 2020. She joins TeleMed2U in our mission to provide increased access to healthcare.

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