DM

I googled and found this http://neuro.vetmed.ufl.edu/neuro/DM_Web/DMofGS.htm  It's an American site but it explains it ok. I knew I'd heard of the disease and now can remember why. A friend's dog had it and they made the decision to let him go with dignity, before it became too hard to handle. Quality of life was paramount in their decision, not only of the dog in question, but of their other GSD. Though I think he'd had it for a while before they let him go. Only you can make the decision on what to do, but be guided by your vet.

Thinking of you.