I get this too....once every few months. It happened the other day and it was the worst episode yet. This time I went to the ER because I really thought it was heart related, but low and behold, all tests came back negative. It is a sensation that cannot be put into words, and I don't think anyone can understand it unless they have experienced it. All of that being said, I just really wanted to share something. My episodes start in my teeth...the same 2 teeth on opposite sides of the lower part of my mouth, and I have a root canal in each of those teeth. I wanted to share this because I so many people here said that they thought they needed to have a root canal in the tooth/teeth that in which they were experiencing this issue. Evidently, I am proof that this is not the answer. I am so thankful to have found this page because it is good to know that I am not alone and there has got to be an answer, a reason, a root cause for what we are going through. I had honestly thought that my root canals might be the root cause, until I read what so many here have shared.