I have pondered this a lot and thought I was sure and always said it was the house fire I went into in 1999, 6 months later I have suffered from MS SX ever since, and then I read about back injuries and Nero the Neuro said that possibly the house fire triggered it, and it may of been with me since 82 when I broke my back, then I think of times as a kid when I had this heavy tight chest feeling, that the docs seem to attribute to my MS cause they cant find any answer for it, so as time goes on I wonder less, cause there are too many factors of could be's