if you had a car accident, I'd be interested to know if the doctor sees nerve damage as a partial reason for muscle atrophy. I had a friend who had a neck injury which basically shut off one of his nerves...The nerve fed his lateral deltoid muscle on one side, so the guy had a rapid atrophy and basically a non-functional medial deltoid which was visible absent. There's nothing he could do about it because it was a permanent nerve issue. If your doc hasn't explained things well enough, he needs to speak in a way anyone can understand. If he knows the reason, ask him to say it another way so you can grasp what's happening to your body and what if anything you can do to improve the situation..