First welcome,, there's lots of good people here and even better advise.
Ok, I have not had a Gamma Knife so I can not speak from experience on this one,,however do your homework. Make sure this MD has had good results with this procedure. Sometimes MD's just get to like a certain procedure over another, not that it's necessarily better for the patient..surgeons are surgeons and their job is to cut (or do procedures), remember that, It does not always means that's the best thing for you.
Get a second opinion, always. When you are considering any procedure, always get a second opinion, it's in your best interest. That doesn't mean don't do it, it just means that you want to see if anyone else thinks of something else.
I developed ATN quickly and My approach was aggressive. I read everything I could and thought I understood this disorder and decided that surgery was my best option. And then the MVD made it worse....so just as word of caution surgery is not always the best move.
Have you considered a good pain management clinic??? You seem to have been through the doctor mill however, if you are near a major hospital that has a pain clinic that is run by anesthesiologists then I would suggest go there before you commit to a procedure. They have access to meds that other MD's can't use that can be very successful. I spent years (and still see) in a PM clinic and it saved my life in many ways.
I offer this only because gamma knife can create some problems down the road. I have known many people who have had successful gammas and years later are on a low dose med program and are fine,. However they are finding that with some people they are having to go in surgically and remove scar tissue after a gamma knife (years after ) that is something to factor into your decision..
I don't want to scare you just inform you,,,I still think I'd give PM a try before you try a procedure if you can,,at least give it a thought. I ended up having to get a PNS system (saved my life) however that is still an experimental procedure and there are only a few clinics in the country that do them and do them well.. However you might consider reading the thread on PNS and see if that is something that you might want to look into.
Whatever you choose,,good luck. We are all here to help,,,Beth