Indications
Thymic mass – this includes thymomas and thymic cysts. The aim of resection of the thymus is to completely remove the thymic mass.
Myasthenia gravis – thymectomy is indicated for this condition when medical treatment fails, in younger patients with short duration of symptoms,
and in patients who have difficulty tolerating the side effects of the medications used to treat myasthenia gravis. Of historical note is that thymectomy for myasthenia gravis was pioneered by Alfred Blalock at Johns Hopkins Hospital in 1939.
Pre-operative Workup and Preparation
Computed tomography – this is almost always obtained pre-operatively if a mediastinal mass is suspected and includes contrast enhancement to evaluate the involvement of the nearby vascular structures.
Magnetic Resonance Imaging – most centers who perform a large volume of thymectomies also routinely obtain this imaging study.
Surgical Details of Procedure
The “standard” thymectomy uses a partial upper sternal-splitting incision in contrast to a transverse cervical (neck) incision or a complete sternotomy with cervical extension.
1. A short incision in the skin of the anterior chest wall in the midline running from just below the sternal notch to the third interspace (at the level of the space between the 3rd and 4th ribs is made with a No. 10 blade.
2. A sternal dissection is done through the subcutaneous tissues with the Bovie cautery.
3. A sternal saw is used to divide the sternum to the third intercostal space and to completely to divide the manubrium.
4. A sternal retractor is placed and opened and the top of the incision is retracted cephalad (toward the head).
5. The anterior surface of the thymus is then visualized and an inspection for a thymoma is undertaken.
6. If a thymoma is found most surgeons will do a complete sternotomy so that a radical excision of the thymus can be performed.
7. Using both blunt and sharp dissection the edges of the thymus are freed from the pericardium (sac surrounding the heart).
8. Care must be taken when removing the thymus from the bilateral mediastinal pleura (lining around the lungs).
9. Care must be taken to identified the phrenic nerves running on both sides of the surgical field and to avoid injuring these structures.
10. After mobilizing the thymus from the pericardium and pleural surfaces the lower poles should be easily retracted cephalad (toward the head).
11. At the lateral margins of the thymus the internal mammary arteries are identified.
12. These are doubly ligated (tied) with 2-0 silk ties and divided.
13. The cervical extensions of each thymic lobe are removed with the body of the thymus by gentle traction and division of the thryothymic ligament.
14. The thymic vein empyting into the innominate vein is visualized and doubly-ligated with silk ties.
15. The thymus is then removed.
16. If at any point of the dissection there is a thymic mass discovered a full sternotomy is usually done.
17. If there is is adherence or invasion of the mass into an adjacent structure the thymus tissue is removed en bloc if possible.
18. Tissue specimens should be sent to the pathology lab for frozen section analysis to assure tumor-free margins if possible.
19. Before closing a thoracostomy drainage tube is placed in the anterior mediastinum.
20. The sternum is then reapproximated with sternal wires and the subcutaneous tissue is closed with a 2-0 Vicryl stitch and the skin is closed using a running 4-0 Monocryl subcuticular suture.
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