Myasthenia Gravis Learning Zone
Transcript: Thymectomy in MG
Joshua Sonett, MD
Interview recorded May 2026. All transcripts are created from interview footage and directly reflect the content of the interview at the time. The content is that of the speaker and is not adjusted by Medthority.
Hello, I'm Joshua Sonett, Professor of surgery at Columbia University Medical Center, Chief of General Thoracic Surgery and Director of the Price Center for Comprehensive Chest Care at New York Presbyterian Hospital. I'll be talking to you about thymectomy, a practical pre- to operative management roadmap for patients with myasthenia gravis. Thank you for your attention. Extended thymectomy for myasthenia gravis is now the only proven surgical treatment for myasthenia gravis. There was an important international trial that was prospective and randomized that definitively proved that for patients with clinically proven myasthenia gravis and acetylcholine positive antibodies, they had significantly better clinical outcomes at three and even late follow up five years and longer for patients with myasthenia gravis, making this a core aspect of treatment for patients with myasthenia gravis. But not all myasthenia gravis are the same. They come in different subtypes and in different pathologic etiologies. So just as we stage and assess for lung cancer, we need to stage myasthenia gravis. And it's generally staged by the antibody type, the clinical presentation, and the age of the patient. Predominantly 75% of patients with myasthenia gravis will have acetylcholine receptor antibodies that are positive. Patients, however, can have what's called MuSK positive myasthenia gravis or lipoprotein receptor 4.
And then some patients, we cannot measure any antibodies. Patients with acetylcholine receptor antibodies have the best response to the thymectomy. Patients with muscle-specific kinase receptor and lipoprotein 4 receptor don't respond very well to thymectomy. Patients with seronegative can respond but also may not respond. It's a mixed bag. The Osserman classification score grades patients how they present. So 1 is purely ocular, and 5 is near death on a respirator. 2, 3, and 4, different gradations of increasing muscle weakness and effect of the patient. For the most part, we do not operate on Osserman classification 1 because they're doing too well, or 5, because they have to be significantly improved medically. 2, 3, and 4 are the target patients that do best with myasthenia gravis and of those patients. Patients with Osserman classification 3 and 4 need significant preoperative optimization to improve their outcomes. Patients can be early or late onset depending on when they present. So basically less than 50 or greater than 50, and patients in less than 50 years of age tend to do better.
A summary of my assessment from clinical data of how patients respond to myasthenia gravis. They're sort of overall best benefits. So acetylcholine positive, early onset age 18 to 50 have a five-star response to the thymectomy, and the thymectomy results will make themselves evidence about at least one year after the thymectomy. Acetylcholine positive but late onset over than 50 still have a benefit, but not quite as good as the young patients. Seronegative early onset can do very well with thymectomy and are good candidates. Seronegative late onset older patients can have a response but have a much less intense response or good results from thymectomy. So consideration should be made when discussing surgery with these patients. There's two types of juvenile, less than 18-year-old patients with myasthenia gravis.
Those that are acetylcholine positive and they can do well, and those that are seronegative that don't do well. Ocular well-controlled, generally can be managed medically. Ocular poorly controlled can be managed with surgery and medicine. And as noted before, MuSk and LRP-4 are not great candidates. Preoperative planning, you need to measure pulmonary function tests, the negative inspiratory force, Osserman classification, and significant bulbar symptoms. If any of these are not optimized, the patient should not undergo surgery at that time, and they should be optimized by your neurologist with maximal dosing of prednisone, mycophenolate, and then if they're really sick and prominently, a significant portion of the patients will need IVIG or plasmapheresis. More recently, new biologic agents are key to their treatment. It's important to know when you're talking to your surgeon that thymic tissue is not one gland. The thymus predominantly is located in these black lobes in the mediastinum, but thymic tissue is seen throughout the mediastinum. So you need to talk to your surgeon, and surgeon needs to understand that any approach to thymectomy, and that's almost certainly minimally invasively now, be it robotic or be it scopic, needs to include all the extra tissue to get maximum benefits of thymectomy. I thank you for your attention.
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