The brain emergency that recently felled U.S. Sen. Tim Johnson, D-S.D., was due to a congenital arteriovenous malformation (AVM). AVM is “a tangle of blood vessels in your brain,” said Dr. E. Sander Connolly, one of two vascular surgeons at Columbia University Medical Center who specialize in surgery involving AVMs.
Usually, arteries and veins are connected via a system of tiny capillaries, where the oxygen in the blood is dispersed into hungry tissues and the blood itself is drawn into the vein for the return trip to the heart. Very rarely, likely in the course of development in the womb, an artery and vein connect directly, with few or no pressure-release intermediaries. As the person grows, the malformed bundle also can grow, and the years of high-pressure blood streaming into the veins built for lower pressures can eventually damage the vein’s walls.
One-half of 1 percent of the population has an AVM in their brains or brain stems, estimates the National Institute of Neurological Disorders and Stroke. The vast majority don’t know they have them, and for most, that’s okay. But for about 12 percent of people with AVMs, roughly 36,000 in the United States, the abnormal bundle of blood vessels causes trouble, sooner or later—putting pressure on sensitive areas or cracking and bleeding, as in Sen. Johnson’s case. For one percent, about 3,000 people, the condition will prove fatal, someday.
Sometimes there are no symptoms that something is going wrong, but if there are they usually are plain to see. “Seizures are pretty obvious,” Connolly says. “Or if you are having the worst headache of your life.”
Because such an abnormality can grow anywhere, be small or large, be deeply embedded or on the surface, and a host of other variations, it is difficult to predict when an AVM will bleed, if ever, or what would happen after it did. But immediate, or nearly immediate, surgery (as Sen. Johnson had) is rare, occurring less than one-third of the time even in emergency cases, Connolly says.
“In the setting of bleeding, we usually wait for the bleeding to resolve,” that is, to stop, and for the swelling to go down, he said. Unlike aneurysms, where the first sign of bleeding often signals more soon to follow, the chance of an AVM “re-bleeding” (causing another hemorrhage) right away is slim, so the neurology team usually waits to get a true picture of what’s wrong. “It’s hard to know. There are so many details,” Connolly says. The wait is usually about a week or so, with wide variations either way.
If the neurology team does decide a person needs emergency surgery, doctors might be able to take out the knot then and there, if it is small, close to the surface of the brain or in a less-critical area and linked to fewer other veins. If not, they stanch the bleeding, close up the skull and wait and watch.
The team usually takes a lot of pictures. Common tests include computed axial tomography (also called CT scans or CAT scans), which take X-ray images from different angles and join them together to show cross-sections of the brain; magnetic resonance imaging (MRI), which uses magnetic and radio waves to detect changes in tissues and to record the pattern and velocity of blood and cerebrospinal fluid; and angiograms, which are X-ray images of arteries and veins after doctors have injected dye into them to find leaks and to observe blood flow.
Based on where the tangle is in the brain or brain stem, how big it is, how tightly knotted it is and what overall shape the patient is in, there are a range of possible next steps. The first is to continue to wait and watch. There is some risk in the treatments themselves, whether surgery, chemotherapy, radiation or injecting dyes and blockers via catheters, and if the risk of bleeding is judged to be low it may well not be worth it to bother the brain further. Next month, Columbia is starting a long-term, federally funded research program to try to create a gauge of the risks of treating versus not treating AVMs.
If doctors agree that the AVM should be treated, they are likely to use one of two main methods: radiation or surgery. Both may be done in tandem with embolization, in which doctors use a catheter through the artery system to the site of the tangle, then inject a substance—usually a sort of glue, or coils or tiny balloons—to close off the blood flow to that area. Less flow can cause the area to shrink and reduces the chance it will bleed even if attacked by scalpel or radiation.
Around 40 AVM surgeries are performed a year at Columbia, which is a center for such cases, Connolly said. These are difficult cases and require highly skilled teams to prepare and perform the procedure. Sen. Johnson’s surgery took five hours.
If the AVM is taken out, the person is considered cured, Connolly said. If it is treated with radiation, a cure can take several years. If watched, people usually come in once a year for checkup.
That’s the treatment part. As for recovery, that also depends on where and how big the AVM is and how healthy the injured person is. Most people recover most of their abilities, but it can take weeks or years and doctors can’t predict it well.
As for Sen. Johnson, “whether or not he’ll be able to work, to get back on the floor of the Senate, it’s way too early to tell,” Connolly says. “From what we know, it’s unlikely that he is going to recover right away.”
And from now on, as with all people diagnosed with AVMs, Sen. Johnson and his doctors will need to watch for signs or symptoms that could signify more bleeding or a greater risk of bleeding. After their first diagnosis and treatment, most people return for check-ups every six months, gradually stretching out to once a year.