I'm beginning to think mine might have something to do with acid reflux or Gerd. I was diagnosed with it like 6 months ago but never really put the two together for some reason. It's hard for me to remember because I don't really get heartburn which I thought was weird. But after my endoscopy they told me I had significant scarring in the esophagus. So.. not saying that this is your cause (or even mine for that matter) but just something to think about if you have acid reflux or suspect you do.
Also, B-vitamins did help a little for me at first, but after awhile didn't seem to have a lot of affect.