Billy - I have a problem at C5-6, too and have the brachial plexus and shoulder problems. When C5-6 is acting up, all the symptoms are significantly worse than the symptoms from the other areas. It causes muscle spasms in the scalenes/front shoulder area all the way down the arm. I can hardly move the arm when C5-C6 is cranky. For me, C5-C6 causes weakness at the shoulder and may contribute to the nerve that runs through the carpal tunnel.

Have you tried a cortisone shot into the neck at C5-6? The reason I ask is based on my own experience. I had a really bad pain period about two years ago in which I finally found a doctor who'd try to treat me (i.e. not tell me to just deal with the pain). The cortisone shots really helped. The other thing the shots pointed out was once my neck area calmed down, the primary driver of my flares was my unstable shoulder (spasms started at the shoulder and proceeded to the neck within 1/2 hour, then to upper back). It was amazing to realize the connection. I've had shoulder surgery to stabilize the shoulder and the neck has been doing so much better.