The cause of cerebral arteriovenous malformation (AVM) is unknown. The condition occurs when one or more brain blood vessels develop in which the arteries connect directly to the veins, without having the normal capillaries between them.

Arteriovenous malformations vary in their size and location within the brain.
There are often no symptoms until complications occur, which involve rupture of the AVM and a resulting sudden bleed in the brain. Sudden bleeding in the brain is known as a hemorrhagic stroke, which is essentially what occurs when an AVM breaks.

If there are symptoms before an AVM ruptures, they are related to smaller and slower bleeding from the abnormal vessels, which are often fragile because their structure is abnormal.

In more than half of patients with AVM, hemorrhage from the malformation is the first symptom. Depending on the location and the severity of the bleed, the hemorrhage can be profoundly disabling or fatal. The risk of bleeding from an AVM is approximately 2-4% per year.

The first symptoms often include headache, seizure, or other sudden neurological problems, such as vision problems, weakness, inability to move a limb or a side of the body, lack of sensation in part of the body, or abnormal sensations. Symptoms are the same as for stroke.

If an AVM bleeds once, the risk is greater that it will bleed again in the future. Intracerebral or subarachnoid hemorrhages are the most common first symptoms of cerebral arteriovenous malformation.

In some cases, symptoms may also occur because of lack of blood flow to an area of the brain (ischemia), compression or distortion of brain tissue by large AVMs, or abnormal brain development in the area of the malformation. There may be a progressive loss of nerve cells in the brain caused by mechanical (pressure) and ischemic (lack of blood supply) factors.

Cerebral arteriovenous malformations occur in approximately 3 out of 10,000 people. Although the lesion is present at the time of birth, symptoms may occur at any time. Two-thirds of cases occur before age 40.

• Headache
  • Sudden and severe
  • Localized or general
  • Resembles migraine headache in some cases
• Vomiting that occurs with headache
• Vision changes
  • Decreased vision
  • Double vision
  • Blurred vision
• Seizures
  • Partial (focal) seizure
  • Generalized tonic-clonic seizure
• Muscle weakness, any part of the body
• Decreased sensation, any part of the body
• Mental status change
  • Sleepy, stuporous, lethargic
  • Confused, disoriented
  • Irritability
• Stiff neck

Additional symptoms that may be associated with this disease:

• Speech impairment
• Smell - impaired
• Movement - dysfunctional
• Fainting
• Facial paralysis
• Eyelid drooping
• Ear noise/buzzing
• Dizziness
• Consciousness - decreased

A complete physical examination and neurologic examination are required to detect abnormal flow in vessels and any focal neurologic signs (weakness, numbness, language problems, visual problems).

Tests that may be used to diagnose AVM include:

• Head CT scan
• Cerebral angiogram
• Cranial MRI
• MRA (magnetic resonance angiography)

An EEG (electroencephalogram) may be performed if symptoms include seizures but are not diagnostic of the specific area of the lesion.

A bleeding arteriovenous malformation is a medical emergency and requires immediate hospitalization. The goal of treatment is to prevent further complications by limiting bleeding, controlling seizures and, if possible, removing the AVM.

Treatment is usually required. Open brain surgery, endovascular treatment, and radiosurgery are some of the treatments used. Often these treatment options will be used in combination. Very large AVMs may short-circuit blood flow enough to cause cardiac decompensation in which the heart is unable to pump enough blood to compensate for bleeding in the brain. In this case, the condition is usually identified in infants and young children.

Surgery is dependent upon the accessibility and size of the lesion and the status of the patient at the time of surgery. Open brain surgery is the actual removal of the malformation in the brain through an opening made in the skull. It must be done by a highly skilled vascular neurosurgeon. This surgery is particularly risky because there is a chance that the surgery itself will cause the AVM to bleed uncontrollably and thereby produce more damage than was prevented.

Embolization (injecting a glue-like substance into the abnormal vessels to stop abherrant blood flow into the AVM) may be an alternative if surgery is not feasible because of size or location of the lesion. Stereotactic radiosurgery may be another alternative treatment for inoperable arteriovenous malformations. It is particularly useful for small deep lesions which are difficult to remove by surgery.

Diagnosis of a cerebral AVM may be made prior to a catastrophic hemorrhage because of recurrent headaches. Early diagnosis is preferable to diagnosis following a catastrophic hemorrhage, which can be fatal or severely disabling. However, since treatment can also be risky, treatment decisions must be made with great care for AVM.

Anti-convulsant medications, such as phenytoin, are usually prescribed if seizures occur.

The expected outcome varies. Approximately 10% of cases which have hemorrhage as the first symptom are fatal. Seizures and neurologic changes may be permanent or may resolve with treatment.

• Intracerebral hemorrhage
• Subarachnoid hemorrhage
• Seizures
• Permanent neurologic changes such as paralysis or sensory problems
• Focal weakness
• Numbness of any part of the face/body
• Vision changes
• Language difficulties
• Persistent headache
• Hydrocephalus ("water on the brain")

Go to the emergency room or call the local emergency number (such as 911) if severe headache, vomiting, seizures, weakness or numbness of parts of the body, or other symptoms suggestive of arteriovenous malformation occur.