Persistent cough for more than a year.

Hello,

I'm posting this for my mom, she's 64. She's had a bad cough for more than a year. When she first started getting it, she went to several doctors. No one could find anything wrong with her. There is no mucous with the cough and she has no pain. There does not appear to be any irritation in the throat. She is not (and has never been) a smoker, and drinks no more than a 1-2 glasses of wine per month. No one in the household has ever smoked. They have a dog, but the dog preceded this condition by years.

The best diagnosis was by a doctor who said that she damaged some throat nerves when she had a flu, and those nerves now replicate the sensation of needing to cough, therefore making her cough. He said it should go away soon, but this was 6-7 months ago. She's seen so many doctors and gotten no-where, she has decided to live with it. But the coughs are scary. They render her nearly unable to breathe sometimes, and now that she has another slight cold, the coughs get even worse, and some coughing fits can last up to 4-5 minutes of continuous coughing. When this happened the other day, it exhausted her so much, she needed to take a nap afterwards.

Any ideas at all?