Summary

Arteriovenous malformation of the brain (AVM) is problem arising in prenatal development that may cause problems such as headache and maybe even serious hemorrhaging in later life. It often goes undetected, however, unless picked up by a routine CT scan. The Center for Endovascular Surgery can deal effectively with such cases with modern techniques and so minimize the risk of serious complications from AVM.

Introduction

The Center for Endovascular Surgery is a division of Beth Israel's Hyman-Newman Institute for Neurology and Neurosurgery. The Center is a world leader in using minimally invasive techniques to treat vascular disorders throughout the body, including brain AVMs, hemangiomas and cerebral hemorrhages. Medical writer R.L, Fielding has contributed this article to HealthandAge on behalf of the Center for Endovascular Surgery.

Characterized by headaches and seizures, an arteriovenous malformation of the brain is one type of arteriovenous malformation, which is a disorder of the body's circulatory system. An AVM of the brain, also known as a cerebral AVM is a malformed group of blood vessels, composed of an intricate tangle of arteries and veins. Though localized, cerebral AVMs can lead to severe neurological problems, Research in the field of AVMs is growing, particularly with noninvasive treatment options.

What are cerebral AVMs?

Cerebral AVMs may form during prenatal stages of a child's development, either during embryonic or fetal growth. Studies have found a certain number of cases form shortly after birth. Cerebral AVMs are commonly misdiagnosed, with most cases found only incidentally through the performance of CT (computed tomography) scans on the brain. Patients complain of regular headaches and seizures before diagnosis.

Other neurological complications can develop including speech and visual difficulty, dizziness, memory deficits, confusion, hallucinations, dementia and difficulty with forward planning. Physical side effects range from loss of coordination, numbness, tingling and spontaneous pain to permanent paralysis. Patients' symptoms are directly associated with the location of the cerebral AVM with certain sites causing hydrocephalus. This is caused by a cerebral ACM preventing the circulation of cerebrospinal fluid thereby causing a fluid buildup in the skull.

What are the potential health consequences of cerebral AVMs?

Hemorrhaging is the most common side effect of patients experiencing cerebral ACM. The size and location of the cerebral AVM determines the patient's likelihood of experiencing hemorrhaging. Research has found that between 2 and 4 percent of all AVMs hemorrhage each year with most episodes going undetected. Minor hemorrhaging does not cause neurological damage, hence patients and doctors are unaware it is happening. On the other hand, massive hemorrhaging has been documented with some cases proving fatal. Once a cerebral ACM bleeds, there is a nine times greater risk of it recurring within the next year. Despite recent research, doctors are still unable to predict whether a patient with cerebral AVM will bleed.

Certain cases do, however, have a bigger risk of bleeding. Smaller adults, for instance, those with high blood pressure and pregnant women have a higher risk. Also, deeply situated AVMs with narrow veins impair proper drainage, leading to an increased risk of hemorrhaging.

Once again, the location of the hemorrhaging AVM is directly proportionate to the side effects of hemorrhaging. Bleeding AVMs are situated deep within the brain and are known as intracerebral or parenchymal cerebral hemorrhages and these cause the most damage.

In addition to hemorrhaging, AVMs on their own can inflict serious brain and spinal dysfunctions. AVMs can reduce the amount of oxygen reaching neurological tissue and compress and displace parts of the brain. The larger the lesion, the greater the chances of such distortions. Indeed, some lesions can reach 2.5 inches in diameter and some have been documented to distort an entire hemisphere of the brain

How is an AVM of the brain diagnosed?

Brain AVMs can be diagnosed with various methods, with the most non-invasive techniques being CT and MRIS scans. Both reveal lesions, while CT scans are particularly helpful in showing hemorrhaging. Three dimensional representations of cerebral AVMs can be detected by CT and MRI imaging.

A more intricate process in identifying an AVM of the brain involves angiography. A contrast agent, or water-soluble dye, is injected into the brain allowing an x-ray to deliver more precise images that highlight blood vessel structure. This procedure carries the risk of causing a stroke, but research has led to vast improvements with angiography thereby reducing stroke potential.

What treatment options are available?

Endovascular embolization is growing in popularity as a non-invasive treatment option for patients with cerebral AVMs. Dr Alejandro Berenstein, the director of the Hyman-Newman Institute is a pioneer in the field of endovascular embolization. This technique involves guiding a catheter through the arterial pathway into the site of the AVM. A substance is injected, reducing blood flow through the lesion. Blood flow reduction makes subsequent surgery safer.

Conventional surgery follows endovascular embolization whereby the central portion of the AVM is completely removed, causing minimal to no invasion of surrounding neurological structures. Deeply situated lesions are not usually considered for conventional surgery. However, Berenstein and others are finding considerable success in finding these deeper AVMs.

Radiosurgery is another option for localized lesions. This involves targeting the center of the lesion with a radiation beam that damages the vessel walls. Over months following treatment, the vessels begin to degenerate and ultimately close.

What is the outlook for patients after treatment?

Embolization and radiation therapy often lead to temporary results. When a cerebral AVM is large, radiosurgery takes months to heal, leaving the patient still at risk of hemorrhage. Research has found endovascular embolization coupled with either conventional surgery or radiation therapy to have the best results. The risk of complication or death is minimized with dual therapy treatments.