When this unfortunate patient had his anterior mediastinoscopy, he later developed protrusion (herniation) of a portion of his lung through the incision adjacent to the sternum (blue). The route used to place the mediastinoscope is shown in green. At the time of the procedure, the left phrenic nerve was also damaged (red). This led to elevation of the left hemidiaphragm (purple), since it had lost the ability to contract. When the diaphragm contracts, it moves downward, so when it has lost its innervation, it moves UP. Complications such as these are quite rare after mediastinoscopy, which is usually a very safe procedure.