I am not a doctor, but the dehydration explanation seems odd to me. It sounds like your son is drinking plenty of fluids.

I haven't experienced some of the symptoms you mention, but I will say that at right about the 4 month mark, I developed a new symptom - muscle spasms and twitches (no pain with them though). It really freaked me out at first, and I still worry about them a bit. When I told my neurologist about them, he didn't seem overly concerned. He made it sound like they were related to the physical and emotional stress of having pcs for several months. Who knows if this is correct. He did tell me I needed to start exercising. Before my injury I was very active, but had basically been sitting around for 4 months due to the pcs. I now exercise at least 4 days a week and the spasms and twitching are less frequent and less intense. I really have no idea if it's the exercise or the fact that I've been feeling generally a little better the past few weeks that's helping. Maybe it's a combo. It could be something to ask your son's doctor about though.