Brain aneurysm is truly something terrible, I lost a friend to it a couple of years ago. (She was 22 at the time and in good health). She just woke up one day in the middle of the night with a headache and had to vomit. On the way to the hospital she fell into a coma and never woke up. Really scary.
Seems like there is something called a Magnetic Resonance Angiography.