Weight cutting, constant hard sparring in training camps and scarring to the brain over time leads to seizures/epilepsy.
Its becoming more commonly reported in contact sports, several AFL players have taken their own lives recently after having an epilepsy diagnosis and keeping it under wraps for a long time.
It generally takes multiple episodes and all sorts of tests to diagnose, hard to fully evaluate after an acquired injury or stress the neurological system.
Some people have an episode and its dismissed for years, then pops up again years later, along with other weird symptoms before an official condition is reported.