When our SWCAH son was two, he had a seizure.  It was because his blood sugar fell so low.  He had been sick with a stomach bug and had vomited a few times.  Although he was getting stress doses of hydrocortisone and seem to be improving, his sugar dropped and he seized.  We are now very careful to check his blood sugar levels when he is sick.  We got a glucose monitor.  Wish you the best.  Michele