I cannot help you as far as the cyst. However, has Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) ever been thought of? What made me think of it was when you posted that your hands curl up, cross your legs, lean on your arms, and use your hands repeatedly for detailed work. And after awhile it minimizes. Here is a very good site on the subject.

http://www.hnpp.org/