Boerhaave syndrome with mediastinal, axillary, neck and epidural free gas
The chest xray and CT show the classic features of Boerhaave syndrome. The mechanism is a focal linear full thickness tear of the esophageal wall following severe vomiting or retching, leading to gas dissecting through the mediastinum. The gas can then escape into other soft tissue spaces. Gas can also dissect into the peritoneal and retroperitoneal spaces.
A CT with oral contrast can be acquired to attempt to identify the site of the leak but often it will have sealed immediately, and to look for mediastinal or pleural collections. Focal esophageal thickening or an intramural hematoma may also be seen.