My husband is 60, has ADHD, had a trauma bike accident (concussion-hit front of head) 14 years ago, recently diagnosed with severe sleep apnea with AHI 88, most of the night in rem stage. Had a grand mal seizure in the middle of the night a couple of days ago--not sure why. No seizures showed on the all night EEG. Head CT and MRI normal for his age group, blood tests normal, vitals normal. Any ideas on what caused the grand mal seizure?