I know this news must be very worrisome for you, but I just wanted to tell you to try to wait for Dr. Scott's feedback before you really trust the MRI.
If just a structural MRI was done (without contrast, and without an MR angiogram) then the results might not tell you a whole lot.
When my daughter, Daphne (almost 2 years old) had an MR Angiogram done three months after her surgery, her neurologist sounded pessimistic (as always). However, when Daphne's surgeon, Dr. STeinberg, saw the films, he was very happy with the results. She had an angiogram a few weeks ago, and her surgeon told us it was one of the best revascularizations he'd ever seen. Which, of course, was great news, but if we'd have just gone on the local neurologists' word, we would have really been discouraged.
I hope I'm not rambling

I just wanted to point out that it takes a Moyamoya specialist to really interpret the tests (and to order the right tests). I hope you hear from Dr. Scott soon --- and I hope you get good news.
Jenny (mom to Daphne www.daphnestory.com)