The aim of this study is to investigate whether minimally invasive thymectomy achieves comparable efficacy and safety results compared to open thymectomy in patients with myasthenia gravis. The planned investigation is a multicenter observational study based on retrospective (present patient data) and prospective data (questionable outcome data).

Primary hypothesis: Minimally invasive thymectomy is not inferior to open thymectomy in terms of efficacy and safety (non-inferiority study).

Based on large cohort studies of the last decades, the thymectomy has become a central component of the immunomodulating therapy in MG patients without thymoma detection. Because randomized studies were missing, remained a residual uncertainty on the importance of Thymectomy. In the study "Randomized Trial of Thymectomy in Myasthenia Gravis" (MGTX-study) published 2016 the effectiveness of thymectomy by patients without thymoma detection has been indisputable confirmed. A significant improvement of the patient's complaints and the reduction of the immunosuppressive drugs were particularly evident by early onset MG (EOMG) two to three years after performing a complete resection of the thymic tissue.

While the MGTX study (with an open operative procedure) was being done, the minimally-invasive thymectomy has gained more and more acceptance. From a surgical point of view, the minimally invasive thoracoscopic procedure represents a gentler alternative. According to the momentaneous clinical-scientific point of view, further studies are necessary to compare both procedures. Furthermore, the MGTX study included only patients with generalized MG and positive anti-Acetylcholine Receptor (AChR)-antibodies, who were younger than 65 years, so that the relevance of thymectomy in other important subgroups, such as late onset MG (LOMG), the ocular MG (OMG), as well as the patients without detected antibodies (seronegative MG patients), who represent about 10 % of whole population of MG patients, is still not clear.

Inclusion Criteria:

• Patients with Myasthenia Gravis
• Age ≥18 years

Exclusion Criteria:

• a proper communication with the patient is not possible
• an informed consent could not be signed
• a patient reject a participation or requires breaking up

Patients with confirmed diagnosis of myasthenia gravis by:

• typical clinical features AND
• antibody diagnostic AND
• positive edrophonium test OR
• abnormal repetitive nerve stimulation OR
• abnormal single-fiber electromyography.

Myasthenia Gravis Foundation of America clinical classification (MGFA classification) of I to V was accepted (class I indicates weakness only in ocular muscles, class II mild generalized disease, class III moderate generalized disease, class IV severe generalized disease and class V a crisis requiring Intubation)

Participants could be taking appropriate anticholinesterase therapy with or without oral glucocorticoids