Minimal Access Approaches to the Mediastinum

Abstract

The mediastinum is the area in the thoracic cavity whose superior boundary is the thoracic inlet and the inferior boundary is the diaphragm. It includes the space lying between the pleural linings of the right and left thoracic cavities, and in it are the heart and great vessels, the trachea and mainstem bronchi, the esophagus, and the neural structures of the para-vertebral sulcus. There are two clinically useful classifications, both of which divide the mediastinum into three compartments. The anterior-superior mediastinum lies in the area behind the sternum anteriorly, the diaphragm inferiorly, and the anterior border of the pericardium posteriorly. Its superior extent goes to the level of the first rib. In this area lie the ascending aorta and its branches, the thymus gland, anterior mediastinal lymph nodes, and fatty tissue. The thyroid gland and parathyroid glands may be displaced from their normal cervical position into the anterior-superior mediastinum. The middle mediastinum is that area bounded anteriorly by the anterior border of the pericardium and posteriorly by the anterior border of the vertebral bodies. The superior extent again goes to the thoracic inlet and inferiorly goes to the level of the diaphragm. In the middle mediastinum are the heart, the pericardium, and the trachea and mainstem bronchi, along with the hilar vessels of the lung, as well as associated neural, lymphatic, and fatty tissue. The posterior mediastinum is bounded anteriorly by the anterior border of the vertebral bodies, inferiorly by the diaphragm, posteriorly by the origins of the ribs as they attach to the joints of the spine and superiorly by the level of the first rib. In this area are the neurologic contents of the posterior mediastinum, including the vagus nerve, the intercostal nerves, and the sympathetic chain. Also in this area are the esophagus, the thoracic duct, the azygous vein, the descending aorta, and associated lymph nodes.^1,2