Complex Surgery Treats Rogue Blood Vessels in the Brain

Multifaceted surgery, integrating innovative approaches in radiology, anesthesia, and surgery is being used to destroy abnormal, dangerous clusters of arteries and veins in the brain by systematically starving them.

Researchers at the University of California San Diego Medical Center (UCSD; USA) developed the surgical technique to treat arteriovenous malformation (AVM) of the brain, which ranges in size from less than 1 cm to almost 10 cm in diameter. The defect can also occur in the spinal cord, and while many patients show no symptoms of the abnormality, more than 10% experience debilitating symptoms; the untreated lesion can be fatal.

Prior to surgery, neuroradiologists attack the growth by embolizing abnormal blood channels, using a catheter that weaves through the tiny vessels before reaching the center of the AVM. The neuroradiologist must be able to visualize the growth in a three dimensional (3D) space, making anterior and posterior turns that are only millimeters in length. To further refine the approach to the AVM, a deep coma is induced before and during surgery; the coma slows the metabolism of the body, reducing blood flow to the brain. By slowing the body's functioning, and causing a slow awakening from anesthesia, the brain has ample time to adapt to changes in blood flow. During the surgery itself to treat the AVM, a section of the skull is removed, and the malformation is slowly and methodically cauterized, guided by a high-powered microscope. Two to five procedures may be required to eliminate the entire lesion.

"In the late 70s and early 80s, medical teams attempted to remove these lesions during a single surgery, frequently encountering catastrophic episodes of brain swelling,” said Professor John C. Drummond, M.D. "Today, with a combination of embolization, the use of a medical coma, and staging shorter surgeries, patients experience consistently good outcomes.”

"It wasn't until the 80s that AVMs were addressed by radiologists as a way of pretreating a patient to improve the results of surgery,” added Scott Olson, M.D. "Now, using catheter-based technology, we can often shut down 50%-80% of the blood vessels that feed the AVM. With 3D rotational imaging, thinner and more flexible catheters, and new liquid embolic agents that better penetrate the lesion, we can more accurately target and eliminate the vessels that lead into the AVM.”

Normally, arteries divide and subdivide repeatedly, eventually forming a sponge-like capillary bed; the capillaries in turn successively join to form veins that carry the blood away. An AVM lacks the dampening effect of capillaries on the blood flow; it also causes the surrounding area to be deprived of the functions of the capillaries such as removal of carbon dioxide (CO2) and delivery of nutrients to the cells. The resulting tangle of blood vessels has abnormally direct connections between high-pressure arteries and low-pressure veins, and can be extremely fragile and prone to bleeding. The resultant sign, audible via stethoscope, is a rhythmic, whooshing sound caused by excessively rapid blood flow through the arteries and veins, which has been given the term, "bruit,” French for noise.

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University of California San Diego Medical Center