What I've seen on this for MS includes the aggravation when lowerig the chin -- does your doctor think it's not MS related because it manifests in your lower back and thighs?
Last appointment, my neuro was actually a little irritated with me because I tried to clarify something I said during my first appointment. I had described something like an "electrical current" running through the back of my neck but when I read up more on symptoms and L'H, it wasn't really the same thing. I've gotten this thing on and off which is not really quite a "shock" -- it's more like someone crumpled up a piece of paper in the back of my neck. Almost like your stomach gurgling but in a different place. But who knows? (And sometimes it actually DOES happen in tandem with my stomach gurgling, LOL!)