Chief Justice John Roberts suffered a seizure today near his summer home in Maine. A neurological workup showed no cause for concern, and doctors diagnosed a "benign idiopathic seizure" -- a diagnosis made more assured by the fact that Roberts had one similar seizure in 1993. He suffered only "minor scrapes" from falling.
Anyone can have a seizure under certain conditions -- high fever, low blood sugar, and sleep deprivation are among them -- and some people have a lower threshold than others, or an "irritable focus" in some part of the brain that can trigger a seizure with particular sensory or chemical stimulation. (I learned this because J has had a handful of seizures in his lifetime. In his case the triggers seemed to be a combination of emotional and visual.) If Roberts' seizures were ever to occur frequently enough to impinge on his work -- which they're not, given that this is his second one in fifteen years -- they could almost certainly be controlled by medication.
In other words: almost certainly no big deal.