This is very similar to what I have been experiencing since a cold I had back in 2001. I cough constantly and sometimes it becomes so violent that I experience cough syncope (pass out cold). I've seen pulmonologists, allergists, neurologists, ENT's, speech therapists, GI's, and a cardiologist. I've had my sinus's carved up, my uvula removed, sleep studies, videostroboscopy, lungs scoped, GI scoped, one year of allergy shots, etc and nobody was finding a cause. Then by a stroke of luck, I was perscribed a drug called Diltiazem for a heart condition that was totally unrelated to the cough. For some reason, the cough was still there constantly, but it was not so violent. Eventually, I met up with a GI doctor that specialized in motility. I went in for a motility study and found that I had distal esophageal spasms that he believes is the cause of the cough. The initial treatment is Diltiazem. Bingo! I still have the cough and I have just tried to live with it. There are some options still to be tried if I want ( Botox injections in the esophagus, and/or lacerations in the esophagus that are supposed to do something...not sure ). Good luck to you. I'll sure be keeping an eye out on this thread to see how things work out for you.