A 3-year-old boy presented to the ED with right pain ear and swelling in the postauricular region that had begun 3 days earlier. His parents reported that the boy had had a whitish discharge from his right ear 8 days earlier, for which the pediatrician had prescribed antibiotic eardrops. Examination The swollen postauricular area was fluctuant and tender (1st image). White secretions were observed in the external auditory canal.

CT scan of the temporal bone (2nd and 3rd image) showed hypointense cystic fluid collection (yellow arrow), and adjacent inflammation (green arrows) in the peri-mastoid area. No signs of infection were noted in the middle ear or mastoid ear. When gentle pressure was applied to the swollen postauricular area, keratin debris and purulence were expressed through the tract and into the osteocartilaginous junction of the ear canal. What are the most likely diagnosis…