Johnston : If you take a look at their blood vessels closely, you'll find one. And we know that smoking is an important risk factor for them. Being a woman is also a risk factor not clear why; and high blood pressure appears to be a risk factor and having a family member with an aneurysm also puts you at risk for having one.
Narrator: Most unruptured aneurysms don't have symptoms, but sometimes people will develop headaches. But they're an unusual, very sudden kind of headache.
Johnston : So, like a thunderclap boom a headache begins. And the other is often it's often the worst headache that anybody's ever experienced up to that point. So, that's another way to trigger someone to thinking, Hmmm, you know, maybe I ought to go in and be seen right away.
Narrator: For Science Today, I'm Larissa Branin.