A 44-year-old woman, with an unremarkable medical history,
presented in the middle of the night with discomfort in her throat.
She described being assaulted by an assailant who put his 'fist
in her mouth', trying to suffocate her. On examination, she had
normal observations and no signs of injury, other than scratch
marks around her mouth; she reported no odynophagia and was able to
swallow fluids readily. During examination, she complained that
lying flat made her increasingly uncomfortable and was causing
burgeoning dyspnoea. She had lateral soft tissue radiography of her
neck as shown in figure 1.
Fig 1. Lateral neck soft tissue radiograph of the 44-year-old
Which of the following is the diagnosis?