Hemorrhagic strokes, which involve bleeds in the brain, make up the remainder.

CNN: Stroke recovery: One woman's story

Their hope is that such a drug would be precious to patients with ischemic strokes and, unlike clot-buster drugs, harmless to those with hemorrhagic strokes.

FORBES: Brain Repair

Activase isn't all that effective against occlusive strokes, and risks killing the patient if in fact he is suffering from a hemorrhagic stroke.

FORBES: Repairing The Brain

But Activase isn't very effective against occlusive strokes, and it even risks killing the patient if he in fact suffered a hemorrhagic stroke.

FORBES: Repairing The Brain