My ears totally stop up when I am having a myesthenic moment. If I sit down, take a mestinon, and rest, they unstop. Somebody said it had something to do with the muscles in your middle ear getting weak. I am not sure if this is true, but I think it is. I use the stopped up ears as a warning sign that I am about to totally lose my voice, get extremely weak legs, and have trouble breathing if I don't slow down.