Arteriovenous Malformations

Most cerebral arteriovenous malformations are supratentorial, usually lying in the territory of the middle cerebral artery. Initial symptoms consist of hemorrhage in 30-60% of cases, recurrent seizures in 20-40%, headache in 5-25%, and miscellaneous complaints (including focal deficits) in 10-15%. Up to 70% of arteriovenous malformations bleed at some point in their natural history, most commonly before the patient reaches the age of 40 years. This tendency to bleed is unrelated to the lesion site or to the patient's, but small arteriovenous malformations are more likely to bleed than large ones. Arteriovenous malformations that have bled once are more likely to bleed again. Hemorrhage is commonly intracerebral as well as into the subarachnoid space, and it has a fatal outcome in about 10% of cases.

Arteriovenous malformations (AVMs) are defects of the circulatory system that are generally believed to arise during embryonic or fetal development or soon after birth. Arteriovenous Malformations consist of a blood vessel "nidus" (nest) through which arteries connect directly to veins, instead of through the elaborate collection of very small vessels called capillaries. Brain AVMs are of special concern because of the damage they cause when they bleed.Arteriovenous Malformations a congenital disorder of the veins and arteries that make up the vascular system . The cause of this disorder is unknown, but is not generally thought to be hereditary , unless in the context of a specific hereditary syndrome. The arteries carry blood rich with oxygen from the lungs, and the veins carry blood back to the heart for recirculation. Each vessel is normally separate and travels in its own pathway.

In patients presenting with subarachnoid hemorrhage, examination may reveal an abnormal mental status and signs of meningeal irritation. Additional findings may help to localize the lesion and sometimes indicate that intracranial pressure is increased. A cranial bruit always suggests the possibility of a cerebral arteriovenous malformation, but bruits may also be found with aneurysms, meningiomas, acquired arteriovenous fistulas, and arteriovenous malformations involving the scalp, calvarium, or orbit. Bruits are best heard over the ipsilateral eye or mastoid region and are of some help in lateralization but of no help in localization. Absence of a bruit in no way excludes the possibility of arteriovenous malformation.

These malformations are most likely to bleed between the ages of 10 - 55; after 55, the chances of bleeding diminishes rapidly. Before 55, the likelihood of hemorrhaging is betweeen 3 and 4% per year (with a death incidence of about 1%). This bleeding can be devastating, particularly in the brain. They can cause severe and often fatal strokes . If detected before the stroke occurs, usually the arteries feeding blood into the nidus can be closed off, ensuring the safety of the patient. Patients have traveled to Mayo Clinic from all 50 U.S. states and from 39 countries for treatment of brain disorders, making it one of the largest treatment centers in the world.

Causes of Arteriovenous Malformations

Some causes of Arteriovenous Malformations:

• The cause of cerebral arteriovenous malformation (AVM) is unknown. The condition occurs when, in the brain, one or more 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. ]
• Most AVMs are not inherited with the exception of a condition called H.H.T. An AVM is not a cancer, and does not spread to other parts of the body.
• Cerebral arteriovenous malformations occurs 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 aged 15-20, but can also occur later in life. Some patients harboring an AVM also have a cerebral aneurysm.
• Families with cerebral AVMs are rare, and such pedigrees have been too small to enable linkage studies. From the few family cases reported, the inheritance appears to be autosomal dominant.

• In a small minority of cases, cerebral AVMs are associated with other inherited disorders, such as the Osler-Weber-Rendu syndrome (ie, hereditary hemorrhagic telangiectasia), Sturge-Weber disease, neurofibromatosis, and von Hippel-Lindau syndrome.

Symptons of Arteriovenous Malformations

Most common symptoms of Arteriovenous Malformations are:

• The person may experience dizziness and may even lose consciousness.
• A seizure in someone who has never had a seizure before is another symptom of AVM.
• 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

Treatment of Arteriovenous Malformations

Surgical treatment to prevent further hemorrhage is justified in patients with arteriovenous malformations that have bled, provided that the lesion is accessible and the patient has a reasonable life expectancy. Surgical treatment is also appropriate if intracranial pressure is increased and to prevent further progression of a focal neurologic deficit. In patients presenting solely with seizures, anticonvulsant drug treatment is usually sufficient, and operative treatment is unnecessary unless there are further developments.

Definitive operative treatment consists of excision of the arteriovenous malformation if it is surgically accessible. Arteriovenous malformations that are inoperable because of their location are sometimes treated solely by embolization; although the risk of hemorrhage is not reduced, neurologic deficits may be stabilized or even reversed by this procedure. Two other techniques for the treatment of intracerebral arteriovenous malformations are injection of a vascular occlusive polymer through a flow-guided microcatheter and permanent occlusion of feeding vessels by positioning detachable balloon catheters in the desired sites and then inflating them with quickly solidifying contrast material. Stereotactic radiosurgery with the gamma knife is also useful in the management of inoperable cerebral arteriovenous malformations. The main treatment are follows :

• This treatment is also known as Radiosurgery or Stereotactic Radiotherapy.
• A narrow x-ray beam is focused on the AVM such that a high dose is concentrated on the AVM with a much lower dose delivered to the rest of the brain.
• The definitive treatment for AVMs is either surgery or focused irradiation therapy.
• Treatment planning for AVMs depends on risk of subsequent hemorrhage, which is determined by the demographic, historical, and angiographic features of the individual patient as discussed above.
• The patient will also be awakened about every hour to check the pupils, test the arm and leg strength and ask questions to test thinking.
• Treatment of AVM may involve surgery to remove the bundle of vessels.
• The patient may not be able to eat at first, so an intravenous line will be inserted into a vein to give plenty of fluid. Medications for pain, sedation and a stool softener likely will be given.
• Arteriovenous Malformations is important to get plenty of rest, so the patient may be in a darkened room and should try to keep as quiet and comfortable as possible.

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