Jan,
Mine is idiopathic so they do not know how it started. Could be any number of reasons but I may never know. I think I have accepted this. I would like to know but more importantly I want my pain to be managed. I've been through (I think) every test out there. I currently take Cymbalta 90mg , Synthroid and Tramadol as needed. As Mrs. D. said though cymbalta and tramadol are contraindicated so be careful if you ask for them. Talk to your doctor. I spoke with both of my doctors and my pharmacist. They said the doses where low enough not to worry.
As for recovery, so far I have been told probably not. I still hold out hope. I believe anything is possible. I just put my trust in Jesus.