Sorry to hear about your wife's nerve pain. I had suggested on another thread that you PM me, and I'd give you some links to good info for trigeminal neuralgia, if that's what she has. (I guess you didn't see my post.)
I was diagnosed with it 6 years ago, and had the "atypical" variety, which mean constant face pain. The classic kind is intermittent stabbing burning electrical etc. nerve pain. Both can be very disabling.
For several years, I was the human guinea pig for trying drugs that might help. But this is how I discovered how sensitive I am to most drugs. Elavil was one of those given. It did, indeed, help the nerve pain! However, it was very sedating for me, even at 10 mgs, and within 3 days, I developed a bad face rash. Which was just as well, since I was too sedated to function.
Elavil is commonly given for pain, especially migraines, fibromyalgia, what have you. I also took it to sleep during my worst Klon w/d's.