Indeed, it's sad but it's great that it's an option.
Interestingly enough, in NB, technically, you have to be competent enough to agree to the procedure AT THE TIME THE PROCEDURE IS ADMINISTERED.
So, in the case of progressive diseases, you have to know ahead of time what the point of no return is, and be sure to have the procedure at that point. Because if the physicians involved cannot say that at the time of the procedure, you were competent to consent, then they aren't supposed to do it.
You can't plan ahead, and say, 'if i'm in this state, please do it'.