The mediastinum is the central compartment of the thoracic cavity, the area inside the ribcage. It is surrounded by connective tissue and contains all thoracic organs – the thymus, the heart and its great blood vessels, the esophagus and trachea, the phrenic and cardiac nerves, the thoracic duct, and lymph nodes.   The mediastinum lies between the lungs and the pleural cavities which surround them.

Thymectomy for Myasthenia Gravis
Myasthenia Gravis is an autoimmune disorder in which there is a defect in the transmission of nerve impulses to the muscles causing a weakness in the voluntary muscles. 

The thymus gland is believed to play an integral in the pathogenesis of myasthenia gravis.  Removal of the thymus (surgical thymectomy) is currently recommended for almost all patients with Myasthenia Gravis.   It has been demonstrated that those patients who have the thymus gland removed, earlier in the course of their disease, tend to experience a relief from their symptoms, although sometimes 6-12 months after the actual surgery.  

The younger patient and those with onlyocular myasthenia are often treated without surgery—at least initially. Similarly, the older patient with mild disease might also be treated without surgery. Any surgical procedure for MG should be designed to remove all thymic tissue. Current popular surgical approaches include a transsternal approach, a transcervical combined with a transsternal approach, a transcervical approach alone and lastly a Video Assisted Thoracic Surgery (VATS) approach.

Thymoma
Approximately 10 to 15 percent of patients with Myasthenia Gravis will have a thymoma.  About 30% of those patients diagnosed with a thymoma will have MG.

Thymoma is a type of cancer that begins in the thymus. The thymus is a small organ located under the breastbone  that makes white blood cells and is considered part of the lymphatic system.  Thymomas can be either benign or malignant. Often, the distinction between a benign and a malignant thymoma is made during the actual surgery by assessing the degree to which the thymoma has invaded surrounding structures.

Many patients with a thymoma are asymptomatic.

The goal of surgery is complete removal of the mass. Surgical approaches to removing a thymoma include a median sternotomy, clamshell incision and more recently Video Assisted Thoracic Surgery (VATS). The minimally invasive VATS procedure is reserved for early stage tumors. As experience with the daVinci robot is gained, a minimally invasive robotic approach to thymoma is considered appropriate for early stage lesions.

Should preoperative studies indicate that the lesion is invasive or malignant, surgeons will not attempt removal using minimally invasive techniques.