Saundra,
I am not a doctor, but I will try to help you unsrestand this movement disorder better. I sounds like it is a condition that causes muscles to move involuntarily. The condition can be caused by many different things, some hereditary and some not. Here is a great website that lists all the possible causes. (If you will notice, under "Vascular" you will find Moyamaoya syndrome)
Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

This website also discusses medicines used for treatment:
"The mainstay of treatment in adults is the class of "neuroleptics," including haloperidol and pimozide....These drugs selectively enhance the function of the indirect pathway by blocking the inhibitory effect of dopamine on this pathway. However, the incidence of side effects in children from neuroleptics has been reported to be as high as 20%. Therefore, it is often safer to start with an alternative medication, such as a benzodiazepine, particularly clonazepam, diazepam, or clobazam. According to reports, certain anti-epileptic medications, such as valproate and piracetam, may improve the symptoms of chorea."
Essentially, it sounds like muscle relaxers may have less side effects than these "neuroleptics". However, I was under the understanding that muscle relaxers could be addictive and quite sedating. Maybe these are the medicines you are talking about. I hope I have been helpful and not too discouraging. I am so sorry that you and your son have to go through such a frustrating, scary condition...on top of MM! I admire your bravery. You both are in my thoughts and close to my heart.
LOL,
Stephanie