What are Arteriovenous Malformations?
Arteriovenous malformations (AVMs) of the brain or spine refer to abnormal connections between arteries and veins. AVMs can be difficult or dangerous to treat and may cause bleeding into or around the brain, most commonly in young adults. Although AVMs can cause headaches or other symptoms, they are often discovered on CT or MRI scans performed for other reasons. Left untreated, there is a 4 percent risk that they may start to bleed, causing severe neurologic damage and even death. Safe, surgical removal of AVMs or treatment with radiation may require partial or complete closure of the AVM through embolization (blocking) techniques. This preparation improves the safety, effectiveness and outcome of surgery.
What Causes Arteriovenous Malformations?
People are born with AVMs, although they do not appear to inherit them from their parents, nor do they give them to their children. It appears that AVMs may be caused by a rupture or clotting of a blood vessel that happens during development before one is born. It is usually not associated with other maldevelopments or with other AVMs.
What Are the Symptoms of Arteriovenous Malformations?
Seizures and headaches are the most generalized symptoms of AVMs, but no particular type of seizure or headache pattern has been identified. Seizures can be partial or total, involving a loss of control over movement, convulsions or a change in a person's level of consciousness. Headaches can vary greatly in frequency, duration and intensity, sometimes becoming as severe as migraines. Sometimes a headache consistently affecting one side of the head may be closely linked to the site of an AVM. More frequently, however, the location of the pain is not specific to the lesion and may encompass most of the head.
AVMs also can cause a wide range of more specific neurological symptoms that vary from person to person, depending primarily upon the location of the AVM. Such symptoms may include muscle weakness or paralysis in one part of the body; a loss of coordination (ataxia) that can lead to such problems as gait disturbances; apraxia, or difficulties carrying out tasks that require planning; dizziness; visual disturbances such as a loss of part of the visual field; an inability to control eye movement; papilledema (swelling of a part of the optic nerve known as the optic disk); problems using or understanding language (aphasia); abnormal sensations such as numbness, tingling or spontaneous pain (paresthesia or dysesthesia); memory deficits; and mental confusion, hallucinations or dementia.
What Is Embolization?
Embolization is a method of plugging the blood vessels of the AVM. Under X-ray guidance, a small tube called a catheter is guided from the femoral artery in the leg up into the area to be treated.
A neurological exam is performed before and after a small amount of medicine is injected. This can help tell if the vessel that feeds the AVM also feeds normal and important portions of the brain. After this, a permanent agent is injected into the AVM and the catheter removed. This is repeated for each vessel that feed the AVM.
During the embolization, the patient is awake but is made comfortable with the help of the anesthesia team that monitors them and gives them medicines by an intravenous line. After the embolization the patients usually spend the night in the Neurological Intensive Care Unit where they can be monitored closely. Patients are usually hospitalized for three nights for each embolization and usually require two or three embolizations at intervals of two to six weeks. Patients resume their normal full activity immediately upon each discharge. There may be some mild headache after the embolization related to the blood vessels of the AVM clotting, or some nausea related to some of the medicines that are given.
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