Hi crazy life! I've had a sleep study before & so had to sleep in all the EEG stuff & they videoed me all night while I slept. I don't know much about why you're having the EEG but if they are in fact videoing you during it, my guess would be that it would be for about the same general reason they videoed me: which was just in case they wanted to reference it after studying your brain wave print out, etc. Basically just another source of information if they see something of interest on the print out, they'd use the video to be able to see you physically at that point in addition to your brain waves.

I hope that helps some! Knowing more facts about something I have anxiety about sometimes helps me, so I thought I'd share.