The Alien in Mark's Throat

Our dear, sweet Mark has had a hard time adjusting to all of the major changes in our lives in the past year. We have worked through most of the issues, and now we have what's left...a nervous tick, if you will. It's similar to when kids stutter, only he doesn't stutter, rather he is constantly clearing his throat, and quite loudly at that. He also makes a sound (similar to a half second hum) on a regular basis (sometimes five or six times consecutively, or roughly 6 times in a ten second period)...we affectionately call it the alien that lives in his throat. And, as Mark has informed us, it brought all of its toys with it, too. And I don't know if you realize it or not, but when an alien moves into your throat and brings its toys, it makes it very difficult to get it to leave. So...I am now asking if any of you have ever dealt with a nervous tick, and do you have any suggestions of ways that I can get him to stop? I thought that with plenty of love and positive reinforcement it would go away on its own, but it only seems to be getting worse. I would love to hear what anyone has to say!