Hi,
I had a "brain zap" when I was drifting off to sleep last night, and it scared me so badly! I've been Googling all morning thinking of course it's epilepsy or a brain tumor, etc. etc.
Then I found these two sources. One is from Wikipedia, but the other is from the Discover channel's website. I feel a LOT better after reading these and hope they can help someone else:
http://en.wikipedia.org/wiki/Exploding_head_syndrome
http://www.discovery.com/area/skinny.../skinnyon.html
aurora