Re: photosensitive epilepsy?
I have photosensitive epilepsy (in addition to other types of seizures). A neurologist will want to do an EEG and get some history on his birth mother, if you have it. An EEG will include flashing lights and will record any unusual brain activity if he is in fact reacting to the lights. Even people without epilepsy can get headaches from playing those video games, so I wouldn't look too deeply into it just yet. In the meantime, I would limit his time with those video games until his testing is completed and you get the results.
Try not to worry, it could be absolutely nothing, but you're doing the right thing by having him checked, especially with his birth mother's history. Please keep us posted.