Strokes and cerebral aneurysms both involve blood vessels in the brain. An aneurysm is a bulge in the wall of a blood vessel. If it bursts, a hemorrhagic stroke can occur. A stroke results from a blockage in a blood vessel, but symptoms can be similar.

An aneurysm often does not cause symptoms unless it bursts or ruptures. Most diagnoses happen during imaging tests for another condition. A doctor will likely monitor the aneurysm and advise a person on how to prevent it from worsening or rupturing.

All cases of stroke and ruptured brain aneurysm are medical emergencies, as they can be life threatening. The symptoms can be similar.

They can all lead to paralysis on one side, a loss of balance, difficulty speaking, and headache. However, an aneurysm or hemorrhagic stroke is more likely to produce a “thunderclap” headache, sometimes described as the worst headache a person has ever had.

In this article, find out about the links, similarities, and differences between an aneurysm and a stroke.

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Some symptoms are the same for a stroke or an aneurysm, but there are also differences.

Symptoms of a stroke

Most strokes happen because of a blocked artery.

A person who is having a stroke may experience:

It is important to call for an ambulance if a person has these symptoms.

Symptoms of an aneurysm

Aneurysms that have not burst do not tend to produce symptoms, but a doctor may diagnose an intact aneurysm during a scan for another condition. However, if an aneurysm becomes large, symptoms can start to appear, and there is a higher risk of it bursting.

Around 30–50% of people say they had a sudden and severe “thunderclap” headache between 6 and 20 days before a major burst, possibly due to a minor hemorrhage or leak. Doctors call this a sentinel bleed. It is a sign that an aneurysm may burst.

Other signs of an unruptured aneurysm include:

  • vision changes
  • pain above or around the eye
  • numbness or weakness on one side of the face
  • speaking problems
  • headaches
  • loss of balance
  • problems with focusing and thinking

Anyone who has a diagnosed brain aneurysm and develops symptoms should seek medical help as soon as possible. The symptoms may be a warning sign that the aneurysm is going to burst with potentially severe consequences.

The symptoms of a burst aneurysm in the brain can range from mild to severe.

Grade 1 symptoms include a mild headache and slight neck stiffness. Grade 5 symptoms include a coma and unusual body position known as decerebrate posturing, where the back is arched, and the arms and legs held straight out.

A ruptured aneurysm can also cause:

It is essential to seek medical help if anyone has a sign of a stroke or a burst aneurysm, as both can be life threatening.

Aneurysm versus stroke symptoms

If an aneurysm has not burst, there are not usually any symptoms.

A burst aneurysm can lead to a hemorrhagic stroke, a key symptom of which is a thunderclap headache.

With an ischemic stroke, a headache can also occur. But, the most noticeable symptoms are paralysis and weakness on one side, difficulty speaking, and facial paralysis or a loss of feeling in the face and upper arm.

A hemorrhagic stroke or burst aneurysm can also involve paralysis and other symptoms, but the thunderclap headache is more noticeable.

There are two main types of stroke: ischemic and hemorrhagic.

An ischemic stroke happens when blood clots, plaque, or other particles block an artery. As a result, blood can no longer reach all the parts of the brain. This is the most common reason for a stroke.

A hemorrhagic stroke results from a bleed. A blood vessel — or possibly an aneurysm — bursts or leaks, and blood enters parts of the brain where it would not usually be, causing damage. High blood pressure can result in a brain hemorrhage and a hemorrhagic stroke.

Around 20% of strokes are hemorrhagic. These can happen when an aneurysm bursts.

An intracerebral hemorrhage involves bleeding into the brain tissue. Around half of hemorrhagic strokes are of this type.

Subarachnoid bleeding happens over the surface of the brain. Blood enters the fluid-filled space between the brain and the underside of the skull bone. Around 85% of subarachnoid hemorrhages are linked to an aneurysm. Around half of all hemorrhagic strokes are of this type.

An aneurysm is a bulge that results from a weakness in a blood vessel wall. This can increase the risk of further weakening and bleeding. In severe cases, the bulge may burst, leading to significant bleeding in the brain.

Aneurysms vary in shape and size. They can happen anywhere, but the most common locations are the biggest artery leaving the heart and the arteries in the brain.

Why does an aneurysm burst and bleed?

An artery in the brain can burst and bleed because the blood vessel walls become weak. This can lead to a hemorrhagic stroke.

According to the National Institute of Neurological Disorders and Stroke (NINDS), about 25% of people with a burst brain aneurysm die within the first 24 hours. In another 25%, it will be fatal within 6 months due to complications.

Survival depends on various factors, including age, general health, and how quickly the person receives medical care.

A person with a ruptured aneurysm also has a risk of:

  • further bleeding
  • changes to sodium levels in the brain, which can cause brain cells to swell
  • an increase in fluid around the brain, known as hydrocephalus
  • vasospasm or contractions in blood vessels in the brain, which can disrupt blood supply
  • seizures
  • brain swelling, known as cerebral edema

These, in turn, can lead to further problems, including another stroke or permanent brain damage.

What causes a brain aneurysm remains unclear, but some research suggests that oxidative stress and inflammation may play a role.

Brain aneurysm

Brain aneurysms can affect anyone, but they appear more likely in people who:

An existing aneurysm is more likely to burst if:

  • it is large or growing in size
  • the person smokes
  • it affects two specific arteries at the back of the brain or one at the front
  • there is a family or personal medical history of an aneurysm bleeding

Ways of reducing the risk of developing an aneurysm or having one burst include:


Here are some factors that increase risk of a stroke:

Steps that can help prevent a stroke include:

  • regular exercise
  • quitting smoking
  • seeking treatment for diabetes, high blood pressure, and other health conditions
  • maintaining a moderate weight

According to the NINDS, it is not always possible to prevent a stroke, but by paying attention to risk factors, 80% of strokes could be avoided.

The treatment options for stroke will depend on the type of stroke. The treatment for a hemorrhagic stroke will be the same as that for a burst brain aneurysm. The treatment for an ischemic stroke will be different.

Ischemic stroke

Treatment for an ischemic stroke aims to restore blood flow and prevent damage to brain cells.

There are many options, such as:

  • drugs to dissolve clots and others to prevent further clotting
  • statins to manage cholesterol levels
  • anticoagulant drugs to prevent clotting
  • drugs to manage blood pressure
  • surgery, if there is severe narrowing of the main supply vessel to the brain

The person will also follow a program for stroke rehabilitation.

Hemorrhagic stroke or burst aneurysm

Treatment aims to stop bleeding and prevent further bleeding, but a person may also need treatment to manage or prevent complications.

Options include:

  • using the drug nimodipine to reduce the risk of further bleeding
  • surgery to close the aneurysm or prevent blood from pushing into it through either neurosurgical clipping or endovascular coiling
  • drugs to manage blood pressure
  • pain management

An intact brain aneurysm

A doctor may recommend treatment for an intact brain aneurysm if there is a risk of it bursting.

If the aneurysm is small or there is a lower risk of it bursting, the doctor will monitor it. The risks of surgery are not worth taking with a low risk aneurysm.

Clipping or coiling surgery may help prevent a high risk brain aneurysm from rupturing. It can stop blood from flowing into the aneurysm.

Any type of stroke or a burst brain aneurysm will need emergency treatment, as both can be life threatening. A doctor may also recommend surgery for any aneurysm at risk of rupturing or monitor a low risk aneurysm.

The prognosis for any stroke or a burst aneurysm varies widely, depending on the severity, how soon a person receives treatment, their age, and so on.

The mortality rate for a hemorrhagic stroke due to a ruptured brain aneurysm is around 25% within 24 hours. Around 18% of people who have a hemorrhagic stroke die suddenly before reaching the hospital. In high income countries, around 15% of people do not survive longer than 30 days after an ischemic stroke.

Those who survive may face long term complications, including a risk of recurrence. There may also be brain damage that affects:

  • movement and coordination
  • speech
  • the ability to think and reason

Recovery can take weeks or months, and a person may continue to experience problems. Ongoing rehabilitation can help an individual remain independent and daily functioning, but some people will need long-term full time assistance.

What are some tips for recovering communication skills after a stroke?

Here are some questions people often ask about strokes and aneurysms.

Are all strokes caused by aneurysms?

No, but 85% of people who have a hemorrhagic stroke — one that involves bleeding rather than a blockage — have a ruptured aneurysm.

Are there warning signs before an aneurysm ruptures?

An aneurysm does not cause any symptoms until it bursts, but warning signs can precede a rupture.

They include weakness on one side of the face, a loss of balance, vision changes, and other symptoms.

Around half of those who have a ruptured aneurysm experience a sudden onset headache 6–20 days before the rupture occurs.

Are all strokes caused by aneurysms?

A ruptured aneurysm is a common cause of hemorrhagic strokes, where bleeding occurs in or around the brain. However, most strokes are ischemic. They happen when a blockage occurs in a blood vessel. An ischemic stroke does not involve an aneurysm.

Aneurysms and stroke are not the same, but a ruptured aneurysm can lead to a hemorrhagic stroke and bleeding in or around the brain.

Symptoms of an aneurysm that has burst or is likely to burst include a thunderclap headache. This is also a sign of a hemorrhagic stroke. Other common symptoms include weakness or paralysis in one side of the face and difficulty speaking and thinking.

An ischemic stroke results from a blockage rather than bleeding in the brain. Any stroke can be life threatening. With rapid treatment, a person can recover. However, they may continue to experience problems with speech, movement, thinking, and other functions.

For this reason, it is essential to seek emergency medical treatment if anyone appears to be experiencing a stroke or burst aneurysm.