Whatever I'm saying is just based on my experience and i dono the technical stuffs.

I have seen aorund 3-4 guys with hiryama desease and all are affected with upper limbs only. Also for all of them the deasease started around 18-20 age. All of us had severe muscle watsage in palm and wrist area more.

Looking @ your post I dont feel it is hirayama.

But stilll it would good to keep away from sports and be in the neck brace for a while. Because reading ur description whenthe neck moves it can cause a wastage.
So be carful for sometime atleast till u get the surgery done.

Because if these get wastened then they may never be back.Thats wat happened to us. SO be careful for some time.