CYST in the posterior mediastinum was once regarded as an inexplicable rarity. To-day, thanks to better radiography, and surgical success within the thorax, fore-gut cysts of the mediastinum are being found more commonly and recognition is being followed by cure. Further, their association both with intraabdominal and with vertebral abnormalities has come to be realized. T h e present study attempts to distinguish the various types of these cysts and to trace their relationship with the other abnormalities. T h e facts now available but not yet widely appreciated are of broad surgical significance, and it is hoped that the hypothesis offered here concerning their development will lead to a clearer understanding of this group of lesions.
CASE REPORTSCase I.-Male, aged 22. This man was referred from an orthopiedic unit where he was undergoing treatment for old-standing injuries received in previous road accidents. A physician was asked to see him because of trivial pain in the anterior part of the chest, and, although physical examination was negative, a chest radiograph disclosed an abnormal shadow in the lower right hemithorax.He was transferred to this Centre and found to be well-developed, muscular, and in good condition ; his only complaints were of a little pain to the left of the sternum in front and some pain down the back of the right leg. Physical examination of the chest failed to reveal any abnormality. Detailed neurological examination was negative (C.S.F. normal, Queckenstedt normal), the Wassermann was negative, and bronchoscopy showed the trachea and main bronchi to be normal. A barium swallow showed that the oesophagus was displaced anteriorly. The barium was then seen to fall to the left iliac fossa and films showed the greatly elongated stomach extending from the diaphragm to the iliac fossa. The chest radiograph (Fig. 634) showed a large elongated mass occupying the mediastinum, and projecting into the right hemithorax at its lower expanded end. The upper part of the shadow seemed to extend into the superior mediastinum above the aortic arch. A right anterior oblique view (Fig. 635) showed that the mass was behind and separate from the cardiac shadow, and it was further noted that there was a posterior gap in the vertebral arch of the second dorsal vertebra. A pre-operative diagnosis of mediastinal tumour was made and operative treatment advised and accepted.AT OPERATION.-The chest was opened through the bcd of the resected eighth right rib. The right pleural cavity showed neither fluid nor adhesions. A large mass was seen to occupy the whole of the posterior part of the mediastinum, extending from the thoracic inlet to the diaphragm. It was covered by mediastinal pleura and constricted by the arch of the azygos vein above the lung hilum ; large thin-walled vessels were visible on its surface. The vagus nerve was seen closely applied to the lateral aspect of the mass, with the larger branches of its pulmonary plexus radiating forwards on the anterolateral surface. The mediastinal pleura was now ...
