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Symptoms of vascular malformations of the brain

What are the symptoms of vascular malformations of the brain?

The symptoms you might experience depend on the type of vascular malformation you have, its size and where it is located in your head. Most of the time, vascular malformations cause no symptoms at all.

The tests and investigations you have might show up other factors which could affect your risk of experiencing any of the symptoms associated with vascular malformations. For example, their exact location and the routes veins take from them.


Strokes affecting people with vascular malformations are usually due to bleeding in the brain (a haemorrhage). The bleeding occurs through the thin blood vessel walls of the vascular malformation. The symptoms of a stroke usually appear suddenly and might be accompanied by nausea (feeling sick), vomiting (being sick) and loss of consciousness.

Main symptoms of stroke:

  • Headache
  • Physical problems in one side of the body (numbness, weakness)
  • Drooping on one side of the face
  • Speech problems (slurred speech, muddled words)
  • Visual problems (blurred vision, loss of vision)
  • Balance problems
  • Confusion

Bleeding in the brain is the most serious complication of a vascular malformation because of the risk of damage to the brain. It is treated as a medical emergency. Sometimes a bleed from a vascular malformation might be so small it causes no symptoms.

The key test for stroke is a CT scan or MRI scan (see Tests and investigations section). Some people might experience stroke-like symptoms despite their brain scans showing no signs of bleeding. This might be due to pressure changes in the blood vessels. These stroke-like symptoms might disappear, persist or gradually get worse over time.

(You might like to read our fact sheet, Stroke, for further information.)

Please note that because further research on the subject is needed, the following figures for the risk of bleeding from vascular malformations are estimates:

• The risk of bleeding from an AVM of the brain for the first time is approximately 1% in any given year. In other words, for every 100 people with an AVM that has never bled, 99 will not have a bleed in the next year and one will.

• If someone has had a bleed from an AVM and received no treatment, the risk of a subsequent bleed is roughly 5% per year. In other words, for every 100 people with an AVM that has bled but not been treated, 95 will not have a bleed in the next year and five will. This risk may vary according to the exact location of the AVM and the way the veins drain from it.

• The annual risk of bleeding from cavernous malformations varies according to their location and whether they have caused a bleed before:

  • Cavernous malformation outside the brainstem with no previous bleed: 0.8% per year
  • Cavernous malformation in the brainstem with no previous bleed: 1.6% per year
  • Cavernous malformation outside the brainstem with a previous bleed: 3.7% per year
  • Cavernous malformation in the brainstem with a previous bleed: 6.2% per year 

• The risk of bleeding from dural AVFs is not well known.

• The risk of bleeding from developmental venous anomalies is very low and certainly much less than 1% per year.

In pregnancy and during labour, the risk of bleeding may be higher for AVMs (although studies have been inconsistent about this). The risk does not seem to be raised for cavernous malformations, and nothing is known about whether the risk of bleeding from other types of vascular malformation is affected.


For people with an AVM or cavernous malformation of the brain, in any given year there is a 1 in 100 (1%) risk of developing epilepsy for the first time.

Epileptic seizures can be caused by a vascular malformation pressing on the brain and causing excessive electrical activity. This electrical activity causes the part of the brain near the vascular malformation to become overactive, resulting in a seizure. There are many different types of seizure and each person’s experience will differ. Vascular malformations in certain parts of the brain (the brainstem and the cerebellum) do not cause seizures.

You might experience unusual feelings and uncontrollable muscle movements in the parts of your body controlled by the affected part of your brain. This is called a partial (or focal) seizure.

You might experience longer seizures that affect the whole of your body with convulsions (jerking or shaking movements). This is called a generalised seizure. You might lose consciousness during a generalised seizure.

You might be prescribed anti-epilepsy drugs to try to control your seizures. There are many different types of anti-epilepsy drugs and the type you are prescribed will depend on your individual situation. You might need to take more than one type. Seizures can often be successfully controlled by these drugs.

(You might like to read out fact sheet, Epilepsy, for further information.)


Headaches are a common problem for a large number of people and it is sometimes difficult to establish whether they are related to a vascular malformation or have a different cause.

People with vascular malformations can have headaches that are similar to migraines and might respond to migraine treatments. The pain can be located at the site of the vascular malformation but it is often felt in a different part of the head.

People with dural AVFs can get different types of headache caused by their AVF irritating the pain fibres in the dural membrane.

If drowsiness, unconsciousness or any stroke-like symptoms accompany a headache you should seek medical attention because of the possibility of a brain haemorrhage.

(You might like to read our booklet, Headache, and our fact sheet, Migraine, for further information.)

Visual problems

Visual problems such as blurred vision, double vision or a loss of vision, particularly affecting one eye, can be a symptom of stroke.

Carotid-cavernous fistulas (CCFs) can cause swelling or redness in an eye and the eye might also protrude from its socket more than usual.

Noises in the head

An AVF of the dura can cause a noise in your head due to the blood flowing through it. The noise is called a bruit. A doctor can hear it using a stethoscope. Occasionally, you might be able to hear the noise yourself. Some people hear it as a distinctive type of ringing or whooshing sound that beats in time with their pulse. This is called pulsatile tinnitus.

Memory problems

If you have had a brain haemorrhage, you might be left with damage to your brain which can cause problems with your short-term memory, attention and concentration.

Even without having had a haemorrhage, people with AVMs sometimes report having problems with their memory. This is possibly due to changes in the flow of blood through their brain.

Anxiety and depression

Although there is no evidence that vascular malformations of the brain directly cause psychological changes, it is quite common for people with this diagnosis to experience anxiety and depression.

People often find it difficult to express how they feel or talk about their emotions but it often helps if you can talk to a friend or relative about how you are feeling rather than keep it bottled up inside. Your doctor or clinical nurse specialist might be able to help. (You might like to consult one of the organisations listed in the Useful contacts section.)

Other symptoms

Other symptoms of vascular malformations of the brain might include speech problems, weakness in the arm or leg, balance problems, and enlarged blood vessels on the scalp.


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