Myasthenia gravis surgery

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Hafiz M. Ahmed, M.D.[2]

The mainstay of surgical treatment of MG is thymectomy, which involves removing as much thymic tissue as possible. It is performed in patients with thymoma and, in nonthymomatous disease, in patients with generalized MG who have acetylcholine receptor (AChR) antibodies. A multicenter randomized trial (MGTX) established that thymectomy plus prednisone improves clinical outcomes over prednisone alone in nonthymomatous AChR-antibody–positive generalized MG, and the 2020 update of the Myasthenia Gravis Foundation of America (MGFA) International Consensus Guidance revised its thymectomy recommendations accordingly.

Thymectomy is indicated in all patients with thymoma (in whom surgery is performed for the tumor itself) and is considered in nonthymomatous patients with generalized MG who have AChR antibodies. ^{[1][2][3][4][5][6][7]}

MGTX was a rater-blinded randomized trial across multiple centers. It included patients under 65 with generalized nonthymomatous MG, AChR antibodies, and disease duration under 5 years. One group received extended transsternal thymectomy alongside a fixed prednisone protocol; the other received the prednisone protocol only. Both primary endpoints, disease severity on the QMG scale and cumulative alternate-day steroid dose, each averaged over time. were better in the surgical group. Reduced use of azathioprine and IVIG and fewer exacerbation-related admissions were also observed. The advantage emerged in year 1, held through year 3, and persisted at 5 years in the follow-on study.

The mainstay of surgical treatment of MG is thymectomy, defined as removal of as much thymic tissue as possible. Endoscopic and robotic (minimally invasive) approaches are increasingly used and have a good safety record in experienced centers. Randomized comparisons between surgical approaches are lacking, but across-study comparisons suggest that less invasive techniques yield results similar to more aggressive approaches; patients considering minimally invasive techniques should be counseled that it is uncertain whether the benefit demonstrated with extended transsternal thymectomy is fully reproduced.^[1][8]

• Early thymectomy should be considered in AChR-antibody–positive, nonthymomatous generalized MG for patients 18–50 years, with the goals of better disease control, lower reliance on immunotherapy, and fewer exacerbation admissions.
• Surgery merits strong consideration when AChR-antibody–positive generalized disease responds poorly to an adequate immunotherapy trial or when that therapy is not tolerated.
• Because it is elective, thymectomy should wait until the patient is clinically stable, given that postoperative pain and mechanics can impair breathing.
• In AChR-antibody–negative generalized disease, thymectomy is an option when immunosuppression is inadequate or poorly tolerated; it is not supported for MuSK, LRP4, or agrin antibody–positive patients.
• For AChR-antibody–positive ocular MG, thymectomy may be offered to those who respond poorly to anticholinesterases and who decline, cannot take, or fail immunosuppression.^[1]

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