Here's a wiki on it:
http://en.wikipedia.org/wiki/John_G._Roberts#HealthChief Justice Roberts suffered a seizure on July 30, 2007, while at his vacation home on Hupper Island off the village of Port Clyde in St. George, Maine.<6><7> As a result of the seizure he fell five to ten feet but suffered only minor scrapes.<6> The fall occurred on a dock near his house, and he was taken by private boat to the mainland<7> (which is several hundred yards from the island) and was then taken by ambulance to Penobscot Bay Medical Center in Rockport, where he stayed overnight, according to Supreme Court spokesperson Kathy Arberg.<8> Doctors called the incident a benign idiopathic seizure, which means there was no obvious physiological cause.<6><7><9><10>
Roberts suffered a similar seizure in 1993.<6><7><9> After this first seizure, Roberts temporarily limited some of his activities, such as driving. According to Senator Arlen Specter, who chaired the Senate Judiciary Committee during Roberts' nomination to be Chief Justice in 2005, senators were aware of this seizure when they were considering his nomination, but the committee did not think it was significant enough to bring up during his confirmation hearings. Federal judges are not required by law to release information about their health.<6>
According to neurologist Dr. Marc Schlosberg of Washington Hospital Center, who has no direct connection to the Roberts case, someone who has had more than one seizure without any other cause is by definition determined to have epilepsy. After two seizures, the likelihood of another at some point is greater than 60 percent.<7> Dr. Steven Garner of New York Methodist Hospital, who is also uninvolved with the case, said that Roberts' previous history of seizures means that the second incident may be less serious than if this were a newly-emerging problem.<9>
The Supreme Court said in a statement Roberts has "fully recovered from the incident," and a neurological evaluation "revealed no cause for concern." Sanjay Gupta, a CNN contributor and a neurosurgeon not directly involved in Roberts' case, said when an otherwise healthy person has a seizure, his doctor would investigate whether the patient had started any new medications and had normal electrolyte levels. If those two things were normal, then a brain scan would be performed. If Roberts does not have another seizure within a relatively short time period, Gupta said he was unsure if Roberts would be given the diagnosis of epilepsy. He said the Chief Justice may need to take an anti-seizure medication.<10>