I see a doc every three months to get injections in my right arm to make my hand relax (or else they dig into my palm). She finds the muscles to inject by sticking a needle that serves as an electrode into the part of my arm the muscle is “supposed” to be and basically wiggling it around until the targeted finger twitches. With me she commonly says “Where the hell is it?” or “That doesn't belong there!” But recently she got a new toy: an ultrasound scanner. She wiggles my finger while trying to locate the corresponding muscle in my arm. Sure enough, many of the muscles in my arm are not where they should be, and some, even when she finds them and sticks the needle in it, which can be seen on the scanner, just do not respond at all.