I would start nightly magnesium rubs... anyway. If he is low, this will compromise the heart eventually. Very low mag levels lead to arrhythmias. (not intending to scare you but it does happen.)

The magnesium topicals began with autistic children, and the Kirkman product was developed over a decade ago for them. The sulfate is also useful for them.

But here on our neuropathy forum we all benefit from fixing low magnesium. It can be so easy to not consume the proper foods, and get low. If this is an autonomic neuropathy, the magnesium would be one of the first things to try.

Here is a wonderful website which gives the content of foods.. You can plug in the things in his diet and see how much of various nutrients he is getting (including the magnesium).

http://nutritiondata.self.com/
pay attention to the serving size too. I use this site all the time, and it is very helpful because it has many common commercial foods/cereals as well.

One thought keeps coming to me... that this may be a dystonia.
This disorder is not well understood, but involves muscles that contract from aberrant signals originating in the brain (or a failure of inhibitory nerve functions/signals). I hope this is not true in your case.

Any questions, you can always Private Message me here. I am also every day on our Peripheral Neuropathy forum.