Thymectomy in myasthenia gravis

Thymectomy is the most usual treatment for patients with a thymoma. A median sternotomy rather than a transcervical approach is now preferred. Also in the experience of Professor Newson-Davis (1), younger (aged less than 40 years), non-thymoma serpositive patients with generalised weakness not adequately controlled by anticholinesterase therapy will often benefit from thymectomy .

Ocular, seronegative or late onset myasthenia are not generally helped by thymectomy (1).

Post-operative care and control of the airway is vital. A nasotracheal tube may be necessary for 1-2 days. Anticholinesterase treatment is best withheld for 24 hours postoperatively. Unresponsiveness to anticholinesterase treatment is suggestive of chest infection and requires prompt physiotherapy and antibiotics.

Following thymectomy, myasthenia gravis symptoms do not generally improve in patients with thymoma; however there may be symptomatic improvement in younger patients with thymic hyperplasia (2)

• in young patients with thymic hyperplasia who have had a thymectomy
  • about 25% go into remission
  • about 50% have significant improvement
  • about 25% do not improve
    • generally improvement following thymectomy is apparent in the first year and may continue for several years

Thymus irradiation may be necessary if the thymoma is malignant.

Reference:

1. Prescribers' Journal 2000; 40 (2):93-98.
2. Prescriber 2005; 16(6): 39-47.