Seizures in Autistic Pt - How to Tell?

[SunnyPupRN]

How can you tell if your autistic pt is having seizures? I have a pt who has a hx of sz but has not had a verified one in several years. The seizures were staring type, probably absence sz. However, he often suddenly breaking into laughter for no apparent reason [gelastic?] or his eyes flicker upwards and his head sort of bobs. He is largely non verbal, so it is difficult to tell if his non responsiveness during these episodes is the PDD. He recently had an EEG -about a month ago - but they were unable to capture sz activity.

Does anyone have a go-to method to sort out autisitic features from non tonic-clonic sz activity?