That's weird because I don't feel a problem in my quads now either...mine starts in the lower hamstring, right behind the knee. It just feels like my foot is flying forward and I can't do anything to slow it down. When I first developed the problem over a year ago, it was always in my quad. Hopefully this means that I'm making progress...
One other peculiar symptom that I have when the problem develops during a run is that I feel a weird funny bone sensation in my right forearm from the elbow to my hand. It only lasts for a second at a time, every couple of minutes. Most people would think that points to MS, but I've already been tested for it.