Just to let you know that I'm having weird thumb issues as well! When I use scissors, the pressure that's applied to the area between my thumb knuckle and the middle joint (where the scissor handle pressure against) causes a tingling feeling to go up my thumb. Very strange, and like you I also worry about MS and things, but I'm trying to put it down to mobile phone and laptop usage, my mobile phone usage has been way too much over the past couple of months. Or I've damaged it somehow.