Causes of nerve pain from the L. thumb-wrist, to the L. Arm bicep, with a swollen 1 in. Lump around Extensor pollicis brevis, with a clear neck MRI?

It could be due to a. several conditions like De Quervain's tenosynovitis which is a painful inflammation of the tendons on the thumb side of the wrist, carpal tunnel syndrome affecting the tendon across the wrist, a radial nerve or other nerve entrapments, or an abnormal fluid collection like a ganglion cyst. See a specialist for electrodiagnostic testing or imaging studies.