Two subject matter experts discuss cases where a thymectomy is appropriate for treating patients with myasthenia gravis.
Dr. James F. Howard: And where does thymectomy fit in the whole thing?
Dr. Nicholas J. Silvestri: Obviously, if when we are making the diagnosis, especially in patients with acetylcholine receptor-positive disease, evaluating everyone for thymic disease, but certainly if someone has a thymoma, they need a thymectomy. That doesn't belong there. And then when it comes to non-thymoma MG, generally speaking, and I think the literature would back me up on this, the benefit seems to be more robust with patients younger than 50 years of age. There are patients that are younger than 50 that I offer that up as an option. There are patients that are older than 50 that ask me about it. I talk to them about my experience with those patients, which mirrors the literature. I don't seem to get a big bang from my buck with thymectomy in the older population. But generally speaking, patients with thymoma are patients younger than 50 I'm offering that up as an option.
Dr. James F. Howard: And so, the patient has generalized disease, ACHR positive otherwise healthy, do you use imaging to help make a decision he needs a thymectomy or not, or she needs a thymectomy or not?
Dr. Nicholas J. Silvestri: I really haven't. The thoracic surgeons have, but I've requested to have thymectomy done on patients with normal imaging and MG.
Dr. James F. Howard: Yeah. And that's our experience so that a normal imaged thymus gland does not preclude the presence of thymic tissue. And we've always adhered to a very radical procedure removing not only the gland but all mediastinal fat from high-up in the neck, all the way to the diaphragm, into the lateral recesses. And it's interesting the amount of thymic tissue that can be found scattered in the fat. And I've heard colleagues talk about, the CT was normal. We're not going to do a thymectomy. And I think that's an error that any benefit that could potentially be derived you've lost that opportunity by leaving it.
Dr. Nicholas J. Silvestri: No, I agree with you. And I would also say that, while as you well know, thymectomy doesn't often allow people to come completely off of medications over time. Often, it's a lower dose. The last few thymectomies I've had performed in patients; they're doing quite well really off of medicine. And it's monitoring them carefully, of course, especially younger patient population, you don't want to really put those people at risk for potential long-term risk with these medications. It is nice to think there are some patients out there that thymectomy was dare I say, curative, but at least quite helpful in controlling their disease.
Dr. James F. Howard: Yeah. And our best responders have been young Caucasian girls.
Dr. Nicholas J. Silvestri: That's my experience 100%.
Dr. James F. Howard: What's the lowest age you've done a thymectomy in?
Dr. Nicholas J. Silvestri: We just recently did a thymectomy on a 14-year-old. And she's done phenomenally. She was a young woman who was basically coming into the hospital in crisis… basically coming in frequently and was on a fairly high dose steroid which led to a number of side effects. We were able to take her thymus out without any complications; taper her off prednisone. She's now down to five milligrams a day. Just about all the side effects have gone away. She's been asymptomatic for months now. She's really benefited. My hope is that we can get her off of that prednisone altogether and hopefully she'll continue to do well with the thymectomy.
Dr. James F. Howard: We've taken it down to age three. And we have a number of patients below 10 where we've done thymectomy on and we have felt relatively, and I'll put that in quotes, comfortable based on thoracic surgery telling us their experience with congenital heart disease. Where in order to get to the major vessels of the heart, they essentially do a thymectomy to expose the heart and the vessels and do the appropriate repair. And these patients do well. There's some basic science literature suggest there's some changes in lymphocyte populations, but over the long-term, clinically, they've done well. We've pushed the envelope down. We try to do it within six to eight months of diagnosis, as long as they're in good shape and will be as aggressive as possible to maximize their strength, to reduce perioperative morbidity. And that seemingly has worked. What sort of approach do you do?
Dr. Nicholas J. Silvestri: it's open sternotomy much like yourself.
Dr. James F. Howard: We've had a surgeon who did that and did not like it. Part of it may have been experience. But I've always had concerns about getting all of the fatty tissue out, particularly in the lateral recesses around the phrenic nerves. And we can only do that with an open procedure. And I'm in the OR with them looking at it and also for my own interest, but that's been our approach too, is an open chest. Would you approach other than mandatory that they must have surgery thymoma any differently? Do you simply take out the thymoma or do you do what's called the thymus thymectomy and take it all out?
Dr. Nicholas J. Silvestri: Yeah, it's the latter. Because again, I think to speak to your point, unless you get it all out, there's a risk that things aren't going to get better. No, it's been more of a radical procedure than I think what's being done in most centers.
Dr. James F. Howard: And for the audience, what we find is that within the thymus gland, they're actually muscle cells that express acetylcholine receptor, and the receptor is a pentamirror, five subunits. And one of those subunits is different. It's a fetal subunit, and we believe that's where the break-in immune tolerance occurs. And so, by leaving it there, even in smallest amounts, one still has the potential for ongoing immunogenic stimulus for antibody production.
Transcript Edited for Clarity