Vascular Lesions of the Central Nervous System

A vascular lesion is an abnormal cluster of snarled blood vessels. Although vascular lesions can occur throughout the body, those located in the brain or spinal cord - the two parts of the central nervous system - can have especially widespread effects on the body. (Read about "The Brain" "The Spine" "Nervous System") According to the National Institute of Neurological Disorders and Stroke (NINDS), central nervous system vascular disorders include arteriovenous malformations (AVMs), cavernous malformations, capillary telangiectases and venous malformations.

Arteriovenous malformations (AVMs)

Arteriovenous malformations (AVMs) are defects of the circulatory system. NINDS says they are generally believed to arise during fetal development (Read about "Birth Defects") or soon after birth. They are comprised of snarled tangles of arteries and veins. (Read about "Vascular System: Arteries & Veins") Arteries carry oxygen-rich blood away from the heart to the body's cells, while veins return oxygen-depleted blood to the lungs and heart. The presence of an AVM disrupts this process.

AVMs of the brain or spinal cord (neurological AVMs) are believed to affect approximately 300,000 Americans. They occur in males and females of all racial and ethnic backgrounds at roughly equal rates, according to NINDS. Most people with neurological AVMs have few symptoms. But for about 12 percent of the affected population, these abnormalities cause symptoms that vary greatly in severity. Sometimes the symptoms are severe enough to become debilitating or even life threatening.

Seizures and headaches (Read about "Seizures" "Headaches") are the most common symptoms of cerebral AVMs. According to NINDS, 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. (Read about "Migraine Headaches") AVMs also can cause other symptoms, depending on the location of the AVM. Signs and/or symptoms may include:

• muscle weakness or paralysis on one side of the body
• a loss of coordination called ataxia, which can lead to problems walking
• dizziness
• visual disturbances and/or an inability to control eye movement (Read about "The Eye")
• aphasia or problems using or understanding language (Read about "Aphasia")
• numbness, tingling, or spontaneous pain (Read about "Paresthesia")
• dementia (Read about "Dementia")
• a bruit or distinctive noise, generally described as a rhythmic, whooshing sound caused by excessively rapid blood flow through the arteries and veins of an AVM. This is usually heard by a healthcare provider during an exam.

NINDS says that researchers have also found evidence that cerebral AVMs may also cause subtle learning or behavioral disorders in some people during their childhood or adolescence. (Read about "Child Development")

Spinal AVMs frequently cause attacks of sudden, severe back pain (Read about "Back Pain"), often concentrated at the roots of nerve fibers where they exit the vertebrae; the pain is similar to that caused by a slipped disk. (Read about "Disk Problems") These lesions also can cause sensory disturbances, muscle weakness, or paralysis in the parts of the body served by the spinal cord or the damaged nerve fibers.

AVMs become symptomatic only when the damage they cause to the brain or spinal cord reaches a critical level. AVMs affect oxygen delivery to the brain or spinal cord because they change normal patterns of blood flow. The flow rate becomes so fast that surrounding tissues don't get the oxygen they need. When starved of oxygen, the cells that make up these tissues begin to deteriorate, sometimes dying off completely. In addition, bleeding can result from this combination of high internal pressure and vessel wall weakness. Very large AVMs can constrict the flow of cerebrospinal fluid - a clear liquid that normally nourishes and protects the brain and spinal cord. As cerebrospinal fluid accumulates, hydrocephalus results. (Read about "Hydrocephalus") This fluid buildup further increases the amount of pressure on fragile neurological structures, adding to the damage caused by the AVM itself.

See diagnosis and treatment options below.

Cavernous malformations

Cavernous malformations (also called cavernous angiomas) are formed from groups of tightly packed, abnormally thin-walled, small blood vessels. The vessels are filled with slow-moving or stagnant blood that is usually clotted or in a state of decomposition. These lesions can eventually displace the normal tissue in the brain or spinal cord. Like AVMs, cavernous malformations can range in size from a few fractions of an inch to several inches in diameter, depending on the number of blood vessels involved.

Cerebral cavernous malformations affect about 0.5 percent of the population worldwide. Some people develop multiple lesions. Although cavernous malformations usually do not hemorrhage as severely as AVMs do, they sometimes leak blood into surrounding tissues because the walls of the involved blood vessels are very fragile. Although they are often not as symptomatic as AVMs, cavernous malformations can cause seizures (Read about "Seizures") in some people. After AVMs, cavernous malformations are the type of vascular lesion most likely to require treatment.

See diagnosis and treatment options below.

Capillary telangiectases

Capillary telangiectases consist of groups of abnormally swollen capillaries and usually measure less than an inch in diameter. Capillaries are the smallest of all blood vessels, with diameters smaller than that of a human hair. They have the capacity to transport only small quantities of blood, and blood flows through these vessels very slowly. Because of these factors, NINDS says that telangiectases rarely cause extensive damage to surrounding brain or spinal cord tissues. Any isolated hemorrhages that occur are microscopic in size. Thus, the lesions are usually benign. However, in some inherited disorders in which people develop large numbers of these lesions, telangiectases can contribute to the development of nonspecific neurological symptoms such as headaches or seizures. (Read about "Headaches" "Seizures")

See diagnosis and treatment options below.

Venous malformations

Venous malformations consist of abnormally enlarged veins. The structural defect usually does not interfere with the function of the blood vessels, which is to drain oxygen-depleted blood away from the body's tissues and return it to the lungs and heart. Venous malformations don't usually hemorrhage, according to NINDS. As with telangiectases, most venous malformations do not produce symptoms, remain undetected and follow a benign course.

See diagnosis and treatment options below.

Diagnosis and treatment options

According to NINDS, angiography provides the most accurate pictures of blood vessel structure in vascular lesions. The technique requires injecting a special water-soluble dye, called a contrast agent, into an artery. The dye highlights the structure of blood vessels so that it can be recorded on conventional X-rays. (Read about "X-rays") Although angiography can record fine details of vascular lesions, the procedure is somewhat invasive and carries a slight risk of causing a stroke. (Read about "Stroke") Two of the most frequently employed noninvasive imaging technologies used to detect AVMs are computed axial tomography (CT) and magnetic resonance imaging (MRI) scans. (Read about "CT Scan - Computerized Tomography" "MRI - Magnetic Resonance Imaging") CT scans use x-rays to create a series of cross-sectional images of the head, brain or spinal cord and are especially useful in revealing the presence of hemorrhage. MRI uses magnetic fields to detect subtle changes in neurological tissues. Magnetic resonance angiography (MRA) can record the pattern and velocity of blood flow through vascular lesions as well as the flow of cerebrospinal fluid throughout the brain and spinal cord.

If a vascular lesion is present, medication can often alleviate general symptoms such as headache, back pain and seizures. Venous malformations and capillary telangiectases rarely require surgery, according to NINDS. Cavernous malformations are usually well defined enough for surgical removal, but surgery on these lesions is less common than for AVMs because they do not pose the same risk of hemorrhage.

The most common treatment for cerebral AVMs is either surgery (Read about "Neurosurgery") or focused irradiation therapy. (Read about "Radiation Therapy") Surgical options for the treatment of AVMs include conventional surgery, endovascular embolization and radiosurgery. The choice of treatment depends largely on the size and location of the AVM. Conventional surgery involves entering the brain or spinal cord and removing the central portion of the AVM. In endovascular embolization, the surgeon guides a catheter though the arterial network until the tip reaches the site of the AVM. Radiosurgery involves aiming a beam of highly focused radiation directly on the AVM. The high dose of radiation damages the walls of the blood vessels making up the lesion. The choice of treatment, and the benefits and risks are things to be carefully discussed with your doctor.