Brain Aneurysm Prognosis

About 68 to 33 percent of people who experience a brain aneurysm rupture survive. And the vast majority of survivors have long term neurological deficits.

The chance that a non-growing brain aneurysm will rupture is about 0.5 percent to 1.1 percent per year, and a growing brain aneurysm has about a five percent chance of rupturing each year. The chance of aneurysm rupture is higher if you have a large aneurysm, have seizures, smoke, have untreated hypertension, or if you drink alcohol.

Brain Aneurysm

An aneurysm is an abnormally shaped blood vessel with a bulging area. The out-pouching is often a weaker, more delicate section in the blood vessel wall. Aneurysms can occur in any blood vessel throughout the body, and a brain aneurysm is an aneurysm located in the brain.

Brain aneurysms range in size, with some being small (millimeters) and some quite large (centimeters).

If you have a brain aneurysm, the biggest concern is that the out-pouching in the wall of the blood vessel may actually rip, tear, or rupture, leaking blood slowly or even pouring blood rapidly into the surrounding brain regions.


A brain aneurysm can cause dramatic symptoms if it ruptures, and mild symptoms or no symptoms at all if it doesn't rupture.

Unruptured brain Aneurysms

Some unruptured brain aneurysms cause noticeable neurological symptoms, such as vision loss, double vision, headaches, or seizures, while many do not cause any symptoms at all. The symptoms are generally the result of the brain aneurysm pressing on a nearby nerve, blood vessel, or another structure of the brain. Symptoms can begin intermittently and may be subtle, or they can be severe, constant, or worsening.

Brain aneurysms that do not cause any pain or neurological symptoms are called asymptomatic brain aneurysms.

Ruptured Brain Aneurysms

Brain aneurysm bleeds are called subarachnoid hemorrhages or hemorrhagic strokes. They can cause throbbing headaches, paralysis, vision loss, loss of consciousness, and even death. The symptoms of a ruptured brain aneurysm tend to worsen quickly over minutes, necessitating emergency medical treatment.


Most brain aneurysms do not cause death because most of them do not rupture. But, when a large brain aneurysm ruptures, there is a high chance of death. The outcome is worse if a brain aneurysm was large before it ruptured, and if it caused bleeding and compression in a critical area of the brain, such as the brain stem.


A brain aneurysm may remain unchanged for the rest of your life, may grow slowly, may grow rapidly, or may rupture and bleed. In some instances, brain aneurysms can shrink or even disappear. This is more likely with smaller aneurysms than with larger aneurysms. Over time, unruptured aneurysms become more stable and less likely to rupture or bleed.

If you have a brain aneurysm, it is not possible to know for sure exactly which path it will follow over the course of the next few years, or over the course of your whole life.

There are several factors associated with a higher chance of brain aneurysm rupture:

  • Increase in size
  • Seizures
  • Smoking
  • Untreated hypertension
  • Previous rupture without treatment
  • Alcohol use


The treatment plan is a very individual high-level decision that you will make with the advice of your neurologist, your neurosurgeon and possibly a neuro-interventional radiologist. As part of your treatment plan, you need to have brain imaging studies to evaluate the size and the change in size of your aneurysm. You may also need surgical repair of your aneurysm.


Follow-up brain imaging is recommended if you have a brain aneurysm. Imaging studies may include Brain MRI, Brain MRA, Brain CT scan, Brain CTA or a cerebral angiogram. Which of these is the best study for you depends on the size and location of your brain aneurysm.

You should make every effort to keep your actual brain scan or images of the scans for later comparison (in case you change doctors or hospitals) because the key to follow up lies in whether the aneurysm changes or grows over time.


Brain aneurysm surgery is one of the most delicate surgical procedures, and it requires careful planning. Surgery may be the best way to prevent bleeding from brain aneurysms that are likely to rupture due to their size, location, or another risk factor.

Brain aneurysm surgery involves placing a metal coil or a clip on the aneurysm in order to shrink the out-pouching by diminishing blood flow. Eventually, the aneurysm withers away, and the blood vessel heals, resuming normal blood flow.


There are some activities than can increase the likelihood of brain aneurysm rupture. Head trauma can trigger bleeding of a brain aneurysm. Extremely high blood pressure, often triggered by recreational drugs such as methamphetamine and cocaine, can cause a brain aneurysm to rupture. Some surgical procedures can also increase the risk of brain aneurysm rupture.

A Word From Verywell

A brain aneurysm is not a simple, routine diagnosis, and it might sound scary. However, if you or a loved one has a brain aneurysm, you should know that there is effective treatment and that there are knowledgeable medical teams who are experienced in brain aneurysm care.

No one can predict your prognosis with exact certainty, but there are some factors that make a brain aneurysm rupture more or less likely, including the size, the location, and the symptoms. And if you are in a high risk group, or even if you are in a low risk group, a number of well- studied interventions can significantly reduce the chances of a brain aneurysm rupture.

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