Arteriovenous Malformation (cont.)
Where do neurological AVMs tend to form?
AVMs can form virtually anywhere in the brain or spinal
cord-wherever arteries and veins exist. Some are formed from blood vessels
located in the dura
mater or in the pia mater, the
outermost and innermost, respectively, of the three membranes surrounding the
brain and spinal cord. (The third membrane,
called the arachnoid, lacks blood vessels.) AVMs affecting the spinal cord are
of two types, AVMs of the dura mater, which affect the function of the spinal
cord by transmitting excess pressure to the venous system of the spinal cord,
and AVMs of the spinal cord itself, which affect the function of the spinal cord
by hemorrhage, by reducing blood flow to the spinal cord, or by causing excess
venous pressure. Spinal AVMs frequently cause attacks of sudden, severe 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. 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. Spinal cord injury by the AVM by either of the mechanisms described above can lead to
degeneration of the nerve fibers within the spinal cord below the level of the
lesion, causing widespread paralysis in parts of the body controlled by those
nerve fibers.
Dural and pial AVMs can appear anywhere on the surface of
the brain. Those located on the surface of the cerebral hemispheres-the uppermost portions of the
brain-exert pressure on the cerebral cortex, the
brain's "gray matter." Depending on their location, these AVMs may damage
portions of the cerebral cortex involved with thinking, speaking, understanding
language, hearing, taste, touch, or initiating and controlling voluntary
movements. AVMs located on the
frontal lobe close to the optic nerve or on the
occipital lobe, the rear portion
of the cerebrum where images are processed, may cause a variety of visual
disturbances.
AVMs also can form from blood vessels located deep inside the interior of the
cerebrum. These AVMs may compromise the functions of three vital structures: the
thalamus, which transmits nerve signals between the spinal cord and upper
regions of the brain; the basal ganglia surrounding the thalamus, which
coordinate complex movements; and the hippocampus, which plays a major role in
memory.
AVMs can affect other parts of the brain besides the cerebrum. The hindbrain
is formed from two major structures: the cerebellum, which is nestled under the
rear portion of the cerebrum, and the brainstem, which
serves as the bridge linking the upper portions of the brain with the spinal
cord. These structures control finely coordinated movements, maintain balance, and regulate some
functions of internal organs, including those of the heart and lungs. AVM damage
to these parts of the hindbrain can result in dizziness, giddiness, vomiting, a
loss of the ability to coordinate complex movements such as walking, or
uncontrollable muscle tremors.
Next: What are the health consequences of arteriovenous malformations? »
- CT Scan (Computerized Axial Tomography) - CT Scan (Computerized Axial Tomography, CAT scan) is a procedure that assists in diagnosing tumors, fractures, bony structures, and infections in the organs and tissues of the body.
- Headache - Learn about the different types of headaches, migraine, tension, cluster, menstrual, and spinal headaches; and their causes, symptoms, diagnosis and treatment.
- MRI (Magnetic Resonance Imaging Scan) - Medical information on magnetic resonance imaging (MRI) used in detecting structural abnormalities of the body. Learn uses, risks, and how to prepare for an MRI scan
Latest Medical News
Neurology RSS