OK, I have come to a tentative decision. I think it is reasonable for me to have a thymectomy if it can be done transcervically. I do not expect it to cure my MG, or even to put me into remission, but there is a good chance that I will see some improvement.

One reason there are no conclusive studies is that "remission" means different things to different people. Some define it as no symptoms and no drugs. Others define it as no symptoms with continuing drugs. But it seems clear that there is good reason to hope for improvement, even for an older, seronegative patient who's had this disease a while. No guarantee, but reasonable hope.

I am going to see if I can meet with the surgeon and ask him:

1) Will imaging studies before the thymectomy help you determine whether mine can be done transcervically?
2) Are you willing to go into this with the agreement that if you begin and find that it can only be done transsternally, you will abort the procedure? For me, the transsternal thing is a deal-breaker.
3) Can this be done with some sort of anesthesia that doesn't involve muscle relaxants?

If he says yes to all three, then I think this is a reasonable gamble for me. I don't expect a remission, but the level of my symptoms right now is such that a noticeable improvement is all I need to live pretty normally. I'm going to call my neuro now and ask for a referral for a consultation.

Thanks, everyone, for talking this out with me.

Abby