My 7 month old has very similar PWS and 3 lasers so far
My 7 month old son also has a PWS on his face, he has had 4 laser treatments so far. I have not noticed a huge lightening yet, but that is just my personal opinion.
They did not do an MRI on my son, they felt he was low risk for SWS based on the location of his PWS.
I finally joined this board tonight, it is nice to find others in the same situation and I am learning a lot by reading these posts.