Is the question that his HD is causing him to do nervous movement? I would think so, but senior dogs can have other issues, too.
Ask you doctor for some Tremadol--at his age, the side effects won't matter. My boss's dog couldn't sit down for months before she died because of arthritis pain. Let's get everyone to sleep over there--get the Tremadol.
Saving just one dog won't change the world . . . but surely the world will change for that one dog (unknown)