-I can't explain it since I'm not a MD, but it's bad news for any musician!! And not that uncommon either, a real risk for anyone who plays regularly.
How to prevent it?
-Warm up before you really start playing. Do some slow and relaxed scales all over the neck. Stretching will probably help too, but warming up is the most important.
And watch out with working on a computer! Using a wrong position for your arms while typing and using a mouse, or just working on a computer too much can cause damage too.
How does it feel?
-I've never had it myself, but it hurts, stingy kind of pain.
How long does it last?
-Depends. I know a couple of people who suffer from it now and then, but it never went away.
How to cure it?
-Physical therapy. And stop doing everything that could have caused it, till you get rid of the problem.