AP

An unidentified woman was in tears during the news conference.

U.S. Chief Justice John Roberts walked out of a Maine hospital Tuesday after the 52-year-old suffered a seizure and fall Monday at his vacation home.

While the White House said Roberts phoned the president telling him he was fine, the incident wasn't the first for Roberts. Roberts had another seizure nearly 14 years ago while playing golf.

A seizure is a sudden surge of electrical activity in the brain. By some estimates, one in ten people will have at least one in their lifetime and over half have no known medical cause.

Doctors do say though that what can provoke a seizure is something many people can control.

"I felt it coming on and I couldn't control it," said Alan Carson, an epilepsy patient. "I didn't know what was happening and I just blacked out."

Carson is among the some 2.5 million Americans with epilepsy. In his case, a tangle of blood vessels in the back of his brain is the cause.

Doctors say in Roberts' case, there is no obvious cause.

"A lot of times, there is no reason found behind the seizure, and so that's good," said Dr. Jay Harvey, epileptologist. "But there can be underlying medical problems or underlying nervous system problems that may cause seizures."

A Presbyterian Hospital epilepsy expert, Dr. Harvey said three things often trigger a seizure, stress, sleep deprivation or dehydration or electrolyte imbalance.

He also said while one seizure may be random, two, as is now the case for Roberts, is a concern.

"This is seizure activity," he said.

An extended EEG may be required to determine a treatment. Advances in therapy often allow epilepsy patients to function completely normally.

When seizure medicines quit working for Carson, he underwent brain surgery,

"[I'm] doing great," he said. "I've not had a seizure since the surgery took place."

E-mail jstjames@wfaa.com