I had a problem with it a few years ago. In my case I developed a case of carpal tunnel syndrome in my left wrist (I play right-handed, fingering with the left), due to an increase in gigging frequency with my band, and lots of computer keyboard time. Went to the doctor, wore a brace, took anti-inflammatory drugs, and seriously considered an operation.

The good news, in my case, was that I was able to correct the problem by correcting my hand positions on the instrument. I was originally a classical guitarist, so I play everything from underneath the neck -- "proper" barre chords, never wrap the thumb over the top, etc. However, playing rock'n'roll style electric guitar leads one to hang the instrument kind of low on the body -- not to look cool, but to facilitate certain picking styles with the right hand. What I discovered was that this made me maintain a pronounced arch to my left wrist (again, picture someone with a low-slung guitar, wrapping his hand under the neck), which gradually caused the tendons running through the carpal tunnel to rub against each other and become inflamed. My solution, paradoxically, was to make changes to my right hand (picking) technique, which allowed me to shorten the strap and gradually ease the strain on my left wrist. I've been problem-free for a few years now.

The particulars of my situation may not apply to you, but three lessons I took away from it might. One, there's a lot you can do by examining the ergonomics of your playing and trying to figure out what you are doing that might be causing or contributing to the problem. Two, the doctors won't necessarily identify the root cause for you -- you may have to figure it out on your own. And three, the situation may well be reversible, which is something a lot of folks don't know and/or believe. Good luck.