What do actor Danny Glover, President Theodore Roosevelt, and singer Neil Young have in common?

All of them have or had epilepsy, disturbances in the brain's electrical activity that lead to recurring seizures.

An estimated 10 percent of Americans will have or have had a seizure at some point in their lifetime. Would you know what to do if you saw someone having a seizure?

Sometimes, the only symptoms are that the person suddenly has a blank look accompanied by facial twitching.

You should calmly guide the person to a safe, quiet place. If he or she is agitated, speak calmly. Call 911.

Some seizures are more active: A person having what's called a generalized seizure may cry out, fall, jerk and become unaware of his or her surroundings.

Some forms may interfere with regular breathing. The person may collapse suddenly. Incontinence can happen. Here's what to do:

• Turn the person on his or her side to help breathing. Loosen anything around the neck.

• Put something soft under the person's head.

• Remove glasses if wearing, and any other nearby objects.

• Call 911 and seek medical help.

• Do not put your fingers or anything else in the person's mouth. Contrary to popular belief, you can't swallow your tongue.

• Do not try to restrain the person.

There are also nonepileptic seizures that can happen when a drop in blood pressure, an irregular heartbeat or very low blood sugar causes sudden changes in blood flow or glucose and oxygen supply to the brain. Call 911 immediately.