Department: Ask the Experts
Q I heard about Senator Tim Johnson's arteriovenous malformation. What symptoms should I be alert to?
A An arteriovenous malformation, or AVM, is an abnormal tangle of arteries and veins in the brain or spinal cord. According to the National Institutes of Health, AVMs are believed to affect approximately 300,000 Americans. While they are rare, more brain AVMs are being detected over time, because CT and MRI brain scans are commonly performed, sometimes for reasons completely unassociated with the AVM.
However, many people still have symptoms. Approximately 50 percent of AVMs are detected when they start to bleed, which causes a sudden severe headache, along with weakness, numbness, speech difficulty, unsteadiness, or vision loss. The other 50 percent may have a variety of other symptoms or no symptoms. Seizures occur in about 25 percent of cases. Headaches occur in about 15 percent, sometimes mimicking migraine, but it is often unclear if the headache is caused by the AVM. Slowly progressive difficulties such as weakness, numbness, speech difficulty, or vision loss occur in less than 10 percent. Some patients will notice a persistent pulsing noise—what's known as pulsatile tinnitus—in the ear from the blood rushing through the vascular malformation.
AVMs are most common in adults between the ages of 20 and 50. They sometimes show up in children, although this is unusual.
Robert D. Brown Jr.