No, as a general rule, this is absolutely not correct!  Surgery is done on many patients, hopefully prior to a stroke, to provide the very necessary blood supply to the brain.

Your sister-in-law may indeed not be a surgical candidate, but I would strongly recommend sending her test results to a MoyaMoya specialist - someone who sees the disease on a daily basis.  The experts will provide an opinion free of charge.

Dr. Steinberg at Stanford has performed several hundred bypass surgeries.  He is the premier MM specialist on the west coast.  Dr. Scott (Boston) is the leader on the east coast, but he primarily sees pediatric patients.  I have provided a link with Dr. Steinberg's contact information below.

http://www.stanfordhospital.com/FindAPhysician/Search/doc.aspx?doc=894&resultSet=894

Good luck to you as you sort this all out!  You and your family will be added to my prayers, and I hope you can get the answers you need from someone more familiar with MM.

Warmly,
Jill

My son Dane is 12 years old with Downs.
Following his diagnosis (TIAs) in April 05 we were informed that the disease could be treated with blood thiners.

As both Danes corotid arteries were completely blocked we researched the web sites and informed the local neurologist that we were going the seek further opinions. He then referred us to an experienced Neurosurgeon who had no hestitation in recommending surgery.

Quiet the opposite to our original treatment.

Dane has now undergone both right and left STA MCAs and tommorrow with have a third proceedure to have burr holes placed in his mid line section.
All within 7 mths of original diagnosis.

Without the operations, our biggest fear was that Dane could have a major stoke. No one could predict if or when this may occur. His communication is limited now and with every thing else he has been through the thought of ongoing added disabilities such as paralysis would be enornous to overcome.

He may have never been impacted by a major stroke, how do we know, and to put him through these proceedures have been a difficult decision. The decision
was made to reduce the odds of it happening.

It would be astute to seek further opinions. You can then be comfortable with your decision.

PS  Dane is free of SP (the spinal weakness), but I cannot recall it being discussed with any of the neurologists or neurosurgeon ?