Welcome to the board. I an new here too. I wasn't even given a size, other than 2.5 cm (I think). I wasn't given any other sizes. I guess they measured from one end to the other.
Regardless, I chose the Gamma Knife as there is one right here where I live. I had it done 4 weeks ago. I won't have an mri for 6 months so I won't know anytime soon if it worked.
I hope your radiation goes well if that is what you choose. It is much simpler than surgery, based on all I have read on this site, but some people do not have a choice due to the size. I don't feel any different since I had the Gamma Knife. I am still quite deaf in my right ear, have balance issues, and fatigue. I guess it takes a while for things to get better, or maybe they won't. Nobody knows at this point.
Good Luck with your surgery and hope all goes well and you can get rid of the AN sooner than later.
Cheryl