Hi, Nan....

I often wonder about symptoms that only appear at certain times.

Is this swelling only at night? Do you take Neurontin or Lyrica?
These two drugs cause peripheral edema. So do opiates in some people.

Do you have pain with it? Discoloration?

If you have inflammation in the neck, the Prednisone may help.
But...prednisone won't work on edema. In fact one side effect of prednisone IS EDEMA! But this typically takes time, and may not be visible short term.

One thing you can try is to apply locally drugs to the problem area. Flector patches RX or OTC Salonpas, may help and may show you with some improvement, exactly where the problem lies. If you suspect a neck problem, apply the patch on the back of the neck and see if you have improvements.

Carpal tunnel often gets worse at night, and hands may swell.
Wearing the wrist brace at night may tell you something too.

It is easy to focus on a terrible trauma like you had. But there may be other ways to deal with your symptoms. Thinking outside the box may help. If you suspect carpal tunnel, try using Salonpas on the wrist..it may take down inflammation there quickly for you (it does for me). Apply the patch over the inside of the wrist to 1/2 goes up and 1/2 goes down, that is on the thumb side.

Consider TOS when all the symptoms add up to that. I'd keep a journal for a while to record when your hand swells. That may tell you something. (some people get swelling when using MSG or other food additives that they are intolerant of, and also when having alcohol).