"Blood in the brain is very bad," Kenton says. Most strokes occur because of a clot in a blood vessel that can be dissolved with very few long-term consequences because the blood vessel itself stays intact. But once blood starts pouring out of a blood vessel into the brain, the damage is much more difficult to control.
The problem with an arteriovenous malformation is that it is made up of several different blood vessels that are tangled up in each other. So not only do surgeons have to remove the blood, they need to close off as many of the leaking blood vessels as possible. "The prognosis goes down based on the severity of the bleed, the number of blood vessels involved and the success of the surgery," Kenton says. About 30% of people who suffer strokes due to bleeding in the brain die within the first 10 to 14 days.
About 300,000 people in the U.S. are born with these tiny clusters of mixed-up blood vessels, which can be found anywhere in the body and are not necessarily restricted to the brain. Most of the time, they don't cause any problems, but they are fragile and can start bleeding as a result of something as simple as a coughing fit or even just waking up in the morning.