Cynthia,
I'm sorry to hear about your brother's diagnosis, and am sure your entire family is shocked. I hope he can be stabilized soon, followed by consideration for surgery(ies).
Does your brother live in Hawaii, or was he visiting there? Unfortunately, many patients are referred to the mainland from Hawaii, due to less experience with moyamoya in general. There is a neuroradiologist (Dr. Chris Neal) who is quite familiar with MM, but he's at Maui Memorial Medical Center. Outside of him, we often get referrals from Dr. Tom Rogers and Dr. George Powell. As you know, it is often necessary to travel for the ideal hoped-for moyamoya expertise.
Regarding your question of the wait period between stroke and surgery, a decision for that should be made on a patient-by-patient basis.
Knowing that this must be a tense time for you and your family, I'll hope and pray for some good news for all of you - sooner rather than later.
Please don't hesitate to ask if you have other questions. And, you know how to reach me at Stanford if you need a shoulder.

Jill