I experienced that as a child. I had so much that I wanted to say, but I couldn't physically say all of it as quickly as the wheels were turning in my mind. It became easier over the years as my physical skills caught up with my mind, though reading outloud still gives me problems, as I read much faster than I speak... If it's communicating his ideas, perhaps he could type what he's thinking and then discuss it before "losing it" in a burst of insight into something. This has helped me communicate more efficiently, as well as organize my thoughts before presenting them for someone's consideration...
