Hi lynxgal,
I'm no Dr. but there could be a possibility that your son was having seizures in his sleep, and also when he was 2-6 months old. If you haven't mentioned this to his neuro please be sure and tell him there might be a connection. The brain is the most active when a person is asleep and he could have been having seizures.
In regards to the sleep deprived e.e.g. it usually takes about 1 hour or a little longer. Your son will have to stay up all night and then when he goes to have the e.e.g. done they will put electrodes all over his head with a electrical cream. It doesn't hurt at all. After the electrodes are put on him they will possibly start flashing a strobe light slowly and then faster and faster and this could trigger a seizure. The e.e.g. test will be able to read 8 areas of his brain and if there's any problems they will be able to tell what area of the brain the possible seizures are coming from, there have been cases where the brain damage is in to deep for some people and the e.e.g. can't find any problems if that happens the neuro may want to do more tests. Here's wishing you and your son the best of luck. May God Bless You Both!

Sue