I agree with mrsD that you should try to get a hold of that MRI report. There are a lot of different reasons that children get a tic or tics.
My concern is that you've been left with such little information and I personally wouldn't be happy having my child in the care of someone who said "that the 'pull' of the right brain against the left was manifesting itself in the form of these 'tics'". Also, most tics do not need to be treated with medications. Some tics can be self-injurious and problematic of course, but simple motor tics tend to wax and wane and change and sometimes it's better to wait and see how things go. Just my opinion of course.
My concern is that you've not really been told why your son has been experiencing some difficulties.
How old is your son?
A transient tic or transient tics are actually quite common in young developing children between the ages of 3 and 6 I think it is... will check that. Most will go away on their own.
EDITED to add:
This is an old paper but it's regarding Secondary causes of Tics. i.e. tics can caused or associated with other conditions. That's why it's really important you get a hold of that MRI report or even go back and take a list of questions with you and have a really good talk with your son's present doctor.
MEJIA, Nicte I; JANKOVIC, Joseph.
Secondary tics and tourettism
Rev. Bras. Psiquiatr.,
São Paulo, v. 27, n. 1, 2005.