Your title caught my eye , so I'll just mention Thoracic Outlet Syndrome - it can be blood flow compression/impingement and/or nerve compression/impingement.
Affects the hands, arms, neck & can involve shoulders/upper back.

You may want to read about it on our TOS forum (for a crash course on it check the sticky threads there).

http://neurotalk.psychcentral.com/forum24.html