What are the indications for thymectomy in patients with Myasthenia Gravis (MG)?

From the Guidelines

Thymectomy is indicated for patients with myasthenia gravis (MG) who have thymoma and for selected patients with generalized MG without thymoma, with total resection preferred over partial resection, especially for patients with MG 1. The goal of thymectomy is to remove the abnormal thymic tissue that contributes to autoantibody production, leading to clinical improvement in 70-80% of patients, though benefits may take months to years to fully manifest.

Key Considerations

• Total resection is preferred over partial resection, especially for patients with MG 1.
• Open or minimally invasive approaches (e.g., VATS or RATS) are both recommended as the standard of care 1.
• Thymectomy is most beneficial when performed early in the disease course.
• Before surgery, patients should be optimized with medications like pyridostigmine, prednisone, or other immunosuppressants to achieve the best possible clinical status.

Patient Selection

• Patients with thymoma should undergo thymectomy regardless of MG severity due to the malignant potential of the tumor.
• In non-thymomatous MG, thymectomy is typically recommended for patients under 65 years of age with generalized MG who have acetylcholine receptor antibodies, particularly those with recent disease onset (within 3-5 years) and who have not responded adequately to initial immunosuppressive therapy.

Surgical Approach

• The surgery can be performed via various approaches including transsternal, transcervical, or video-assisted thoracoscopic surgery (VATS), with minimally invasive approaches becoming increasingly preferred 1.
• The choice of surgical approach should be individualized based on the patient's specific needs and the surgeon's expertise.

Outcome

• The primary outcome of thymectomy is the reduction of morbidity and mortality from generalized myasthenia gravis, as well as the improvement of quality of life 1.

From the Research

Indications for Thymectomy in Myasthenia Gravis (MG)

• Thymectomy is virtually always indicated in MG patients who have a thymoma 2.
• The evidence for thymectomy in non-thymomatous MG remains less certain, although one randomized controlled trial has been published 3.
• Thymectomy is associated with a sustained improvement of symptoms in the majority of patients, with 34% achieving complete stable remission (CSR) and an additional 33% achieving pharmacological remission 2.

Patient Selection for Thymectomy

• Patient selection for surgery and adequate pre-operative MG control are critical 4.
• Clinicians should discuss thymectomy treatment with patients with AChR ab+ generalized MG 3.
• Patients with a hyperplastic gland had a significantly greater chance of achieving CSR compared to other histological subtypes 2.

Surgical Approach

• Minimally invasive techniques have many advantages over open approaches, provided they are as extensive as trans-sternal thymectomy 4.
• Clinicians should counsel patients with AChR ab+ generalized MG considering minimally invasive thymectomy techniques that it is uncertain whether the benefit attained by extended transsternal thymectomy will also be attained by minimally invasive approaches 3.

Postoperative Outcomes

• Thymectomy for MG is generally safe and well tolerated, with one patient developing postoperative myasthenic crisis in a study of 89 patients 2.
• Post-thymectomy MG can be categorised as early-onset or late-onset form with differing aetiology, and demonstrated correlation between preoperative anti-AChR titres and post-thymectomy MG 5.