You may already have an answer by now, but the arm atrophy and the cervial problems sound like an injury or constriction of the brachial plexus nerve bundle. I had a friend with arm atrophy and pain, and it turned out she had what is called cervical ribs. They are an extra set of ribs that attach higher than ribs usually do - up to the cervical area, and they constrict the brachial plexus nerve bundle because they are in the way. The nerve bundle is made up of fibers that come from C5-T1 (I just looked it up), so a C4-5 repair could have damaged them. If you have had x-rays though, you might want to ask your doctor if they showed cervical ribs. My friend had numerous X-rays and at least one MRI, and no one said, "Gosh! This woman has cervical ribs!" She was going regularly to a neurologist and no one picked up on it. Cervical ribs are rare, and I guess they just didn't know what they were seeing. By the time she went to a doctor who did see and understand what they were, she had permanent damage done to one side, but surgery gave her back most of her movement and nerve control (and pain free) in the other side. (She had bilateral cervical ribs, which is very rare). Surgery is needed to remove the cervical and the 1st rib to keep the cervical rib from regrowing. I don't know if this helps, or if you are still looking at this site, but I thought I'd better give you the little I knew from my friend.
I have not gotten any response to my original post. tell me more about your symptoms.
THE QUESTION THAT OBERLYUS ASKED ON 1-2-07 ABOUT HIS ARM TWICTHING IS THE EXACT SAME SYMPTOM AS I AM HAVING. I HAVE ALSO HAD THE C5/C4 NECK FUSION. DID HE EVER GET AN ANSWER?
I should add that I am a 57 year old male. In 2001 I had bone spurs taken off my right shoulder. The twitches and strength issues existed long before that surgery and were not lessened after the surgery.
I do not have any pain issues or vision problems, and am not dizzy except when getting off the floor after my morning stretching exercises.