Arteriovenous malformation - cerebral

Definition

A cerebral arteriovenous malformation is an abnormal connection between the arteries and veins in the brain that usually forms before birth.

Alternative Names

AVM - cerebral

Causes, incidence, and risk factors

The cause of cerebral arteriovenous malformation (AVM) is unknown. The condition occurs when arteries in the brain connect directly to nearby veins without having the normal vessels (capillaries) between them.

Arteriovenous malformations vary in size and location in the brain.

An AVM rupture occurs because of pressure and damage to brain tissue, as well as a lack of blood flow to the brain. Symptoms may also occur when large AVMs that have not bled press on the brain tissue.

Cerebral arteriovenous malformations occur in less than 1% of people. Although the condition is present at birth, symptoms may occur at any age. Hemorrhages occur most often in people ages 15 - 20, but can also occur later in life. Some patients with an AVM also have cerebral aneurysms.

Symptoms

Symptoms that may occur with an AVM that has not bled include:

• Decreased sensation in any part of the body
• Headache
  • In one area (localized) or general
  • Resembles a migraine headache in some cases
• Muscle weakness, any part of the body
• Seizures
  • Generalized tonic-clonic seizure
  • Partial (focal) seizure
• Vision changes
  • Blurred vision
  • Decreased vision
  • Double vision

Additional symptoms:

• Decreased consciousness
• Dizziness
• Dysfunctional movement
• Ear noise/buzzing
• Eyelid drooping
• Facial paralysis
• Fainting
• Impaired smell
• Speech impairment

There are often no symptoms until the AVM ruptures. This results in sudden bleeding in the brain (hemorrhagic stroke). In more than half of patients with AVM, hemorrhage is the first symptom. Symptoms of AVM hemorrhage are the same as those of other intracerebral hemorrhage.

Signs and tests

A complete physical examination and neurologic examination are needed, but they may be completely normal.

Tests that may be used to diagnose an AVM include:

• Cerebral angiogram
• Cranial MRI
• Electroencephalogram (EEG)
• Head CT scan
• Magnetic resonance angiography (MRA)

Treatment

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

Treatments include:

• Open brain surgery
• Endovascular treatment
• Radiosurgery

Some treatment options are used together.

Open brain surgery removes the malformation through an opening made in the skull. It must be done by a highly skilled neurosurgeon.

Embolization (endovascular treatment) is the injection of a glue-like substance into the abnormal vessels to stop blood flow in the AVM and reduce the risk of bleeding. This may be the first choice for some kinds of AVMs, or if surgery cannot be done.

Stereotactic radiosurgery is another alternative. This procedure delivers radiation directly to the area of the AVM to cause scarring and shrinkinge. It can control bleeding and other symptoms. It is particularly useful for small deep AVMs, which are difficult to remove by surgery.

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

Expectations (prognosis)

Approximately 10% of cases in which hemorrhage is the first symptom are deadly. Some patients may have permanent seizures and neurological problems.

Complications

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

Possible complications of open brain surgery include:

• Brain swelling
• Hemorrhage
• Seizure
• Stroke

Calling your health care provider

Go to the emergency room or call the local emergency number (such as 911) if you have:

• Numbness in parts of the body
• Seizures
• Severe headache
• Vomiting
• Weakness
• Other symptoms of a ruptured arteriovenous malformation

Also seek medical attention if you have a first ever seizure, because AVM is occasionally the cause of seizures.

References

Zivin JA. Hemorrhagic cerebrovascular disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 237: chap 432.