And we should all get to know these signs of stroke -
* Sudden numbness or weakness of the face, arm, or leg, particularly on one side.
* Sudden confusion, with trouble speaking, or understanding.
* Sudden trouble seeing in one or both eyes.
* Sudden trouble walking, dizziness, or a loss of balance, or coordination.
* Sudden headache with no known cause.
Dr. Rodney Bell, co-director of the jefferson stroke center, says speedy recognition of stroke improves the chance of recovery.
"If you are going to be treated by the only drug available - TPA - recombinant tissue plasminogen activator - it has to be given within the first 4 and a half hours," says Dr. Bell.
He says strokes can be caused by clots, or a ruptured blood vessel.
Sometimes, bulging blood vessels called aneurysms can rupture.
Biden's father had 2 ruptured aneurysms within 3 months in 1988, and needed surgery for each. It kept him away from his U.S. Senate seat for 7 months.
To learn more about stroke , go to the American Stroke Association.