Tile and marble... that takes talent... love them both!
I think your first sentence says a lot of it as to symptoms and what is going on before Ans more than a few mm are discovered. Probably having an MRi with contrast would make a huge difference in having these Ans discovered earlier. I am well aware of other situations that can be the cause but at the same time I am thinking that an MRi as already mentioned would catch these ( and other things) much earlier...
From everything I have heard about MGH i am thinking you are in very good hands.
Finding out about having an An is quite the experience. All sorts of emotions run through us. Looking at how one's life might change is aprt of that. A good thing is when one makes a decision about which treatment after any research one can do, and you have done that it seems, more calm enters. You are, I am sure, in good hands.
Sending you all the best and soon you will be handling tile and marble which makes a lot of beauty in our lives.