The lateral neck x-ray shows air in the retropharyngeal soft tissue. To determine the cause, patient underwent a chest x-ray, which showed pneumomediastinum.
Likely cause in this asthmatic patient was use of illicit drug (snorting). Subsequent CT scan of the chest ruled out esophageal rupture. Patient remained well while under observation and was discharged home 24 hours later.
Further reading https://www.eurorad.org/case/9783