I get the same thing in one or both thumbs when I'm seriously stressed out. Its caused by pressure on the nerves that come out of my spinal cord between vertabra c-5 and c-6. the pressure is caused by a misalignment of my neck resulting from an car accident many years ago. I started seeing a chiropractor about a year ago, and the problem is almost completely been eliminated. Most people's necks have and S curve to them, mine had a reverse S, and consequently the discs in my neck had lost about 75% of the thickness they should have had. My chiropractor has been able to adjust my neck back to almost normal, some of the vertabra are actually deformed, so it'll never be 100%, and I've regained almost 50% of disc thickness. I'm also about 3 inches taller now. Bottom line, I'd see a chiropractor, and I would recommend that you look for one who practices the Gonstead method. They're harder to find because the training is much more rigorous. PM me with your location and I'll see if my doctor can find someone in your area to recommend.