US Chief Justice John Roberts has left hospital to resume his vacation as the mystery over his seizures is dissected by the medical experts.

US Chief Justice John Roberts has left hospital to resume his vacation as the mystery over his seizures is dissected by the medical experts. 2

Chief Justice John Roberts Jr. left a Maine hospital Tuesday, medically cleared to resume his vacation but with the mystery over the cause of his seizure the previous day still unresolved.

Seizure, a condition caused by over-excitation of the brain that can last from seconds to minutes, is a relatively common medical phenomenon. Seizures of varying degrees of severity occur in one out of 10 adults, according to the Epilepsy Foundation.

A Supreme Court spokeswoman has said Roberts had suffered a “benign idiopathic seizure,” in which neurologists find no direct cause of the seizure, such as a tumor or stroke. This diagnosis is made in roughly 70 percent of people who have suffered one or more seizures.

“Idiopathic seizures are usually related to seizure disorders that we think are genetic, somebody carrying a genetic predisposition that will occasionally, under the right circumstances, have a convulsive seizure,” said Dr. John Ebersole, director of the Adult Epilepsy Center at the University of Chicago.

For people who suffer such seizures, the lack of a clear cause can be disconcerting.

“That term is scary,” said Howard Zwirn, a Chicago environmental consultant and attorney who was diagnosed with epilepsy and underwent brain surgery to ease his seizures in 2004. “When I had a heavy seizure, I would go to hospital and have my blood tested, and it would show that I had a seizure, but no source.”

In addition to blood testing, Roberts likely received several other tests following his seizure, including MRI brain scans and electroencephalograms, or EEGS, which measure brain electrical activity. Roberts, 52, also assured President Bush by phone on Tuesday that he felt fine.

Doctors will have also tried to identify a trigger that could have set off both Roberts’ latest seizure and another episode he experienced in 1993, such as sleep deprivation, stress, fever, or infection, Ebersole said.

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