Given the odds of 1 in 10 million, I'm confident that not only am I free of this condition, but no one I've ever met has it either. I'm not even going to take a typing test to prove that I still type at 70wpm (which may be possible to do with one hand, but I don't think anyone could learn it without being conscious of having done so). I will reevaluate this conclusion if a doctor (or anyone, really) tells me they think my left arm is paralyzed.

EDIT: As for an exact number, I am > 99% confident about this, which is high enough that it is not worth it to calculate a better estimate.