Robotic Extended Thymectomy in Late-Onset Myasthenia Gravis: A 21-Year Retrospective Cohort Study of 172 Patients

Abstract

Background: The safety and feasibility of robotic-assisted (RATS) thymectomy for myasthenia gravis (MG) with onset age ≥ 50 years remain unverified, particularly in very late-onset MG (V-LOMG).

Methods: Patients were classified into late-onset MG (LOMG, 50-64) and very late-onset MG (V-LOMG ≥ 65) based on age of onset. Composite neurological remission (CNR) included complete stable remission (CSR), pharmacologic remission (PR), and minimal manifestations-0 (MM-0), while favorable outcomes comprised CNR and MM1-3.

Results: Among 1041 patients, 172 with MG onset at ≥ 50 years who underwent RATS extended thymectomy were included in the final analysis. The LOMG group comprised 104 patients (45.2% male), while the V-LOMG group included 68 patients (60.3% male). V-LOMG patients had more preoperative MG crises, shorter onset-to-thymectomy intervals, heavier thymic specimens, and less hyperplasia. In ocular-onset MG, generalization was more frequent in LOMG than in V-LOMG. No significant differences were found in other baseline characteristics, perioperative parameters, postoperative complications, and adverse composite outcomes. At a 5.1-year mean follow-up, the V-LOMG group had slightly higher CSR (7.4% vs. 6.7%), CNR (16.2% vs. 11.5%), and favorable outcome rates (52.9% vs. 45.2%) than the LOMG group, with no statistical significance. Both groups, especially V-LOMG (16.0 mg vs. 2.1 mg, p < 0.001), showed a significant corticosteroid dose reduction at the last follow-up, confirming the steroid-sparing effect of thymectomy.

Conclusions: RATS extended thymectomy appears to be a safe and feasible treatment for patients with MG of onset at age ≥ 50 years, including those with V-LOMG, demonstrating a significant steroid-sparing effect while maintaining favorable neurological outcomes.

Keywords: extended thymectomy; late‐onset myasthenia gravis; myasthenia gravis; neurological outcomes; robotic‐assisted surgery.

FIGURE 1

Cumulative incidence of CSR (A) and CNR (B) in the two groups. The blue line and shaded area represent the LOMG group (disease onset at 50–64 years) and its corresponding confidence interval. The yellow line and shaded area represent the V‐LOMG group (disease onset at ≥ 65 years) and its confidence interval. CI, confidence interval; CNR, composite neurological remission (CSR + PR + MM‐0); CSR, complete stable remission; HR, hazard ratio; MM‐0, minimal manifestations‐0; PR, pharmacologic remission.

FIGURE 2

Average daily medication usage before and after robotic extended thymectomy in patients with late‐onset myasthenia gravis. (A) Number of medication types administered preoperatively and at the last follow‐up. (B–D) Average daily dose of (B) cholinesterase inhibitors, (C) corticosteroids, and (D) azathioprine at both time points. Data were obtained from institutional records or structured telephone interviews. Solid bars represent the total cohort; striped bars, patients with onset at 50–64 years (LOMG); and dotted bars, patients with onset ≥ 65 years (V‐LOMG). *p < 0.05, **p < 0.005.