Hi, Lora:
Pearchica is correct. If you look at my signature at the bottom of this post you'll see that I had the 'retrosigmoid approach' microsurgery to debulk my 4.5 AN, then underwent 26 radiation treatments (FSR, not Gamma Knife). Because the surgeon avoided disturbing the facial/cranial nerves, I had little-to-no post-op complications. I'm fine, now. I believe the surgery + radiation procedure will become more and more common for dealing with large AN tumors. Trying to 'get it all', as was the case until recently, often caused the surgeon to cut or disturb critical nerves that left the patient with 'damage'. This way (surgery, then radiation) the surgeon can cut down the (big) tumor, cutting off it's blood supply, then use FSR to kill it's DNA. My AN shows definite signs of necrosis, which attests to the efficacy of this approach. My AN symptoms are almost completely gone and my balance is now close to what it once was.
You may want to get a second opinion and not simply accept what this doctor tells you. Frankly, I would question whether you really need a second surgery, with all the possible complications that entails, when radiation is available and proven effective on smaller AN tumors.
I wish you all the best and hope this works out to your ultimate benefit.
Jim