3-Year-Old Boy With Unilateral Facial Swelling

The child is bright and alert and has no fever. The swelling is on the left side of the face only. Find other clues to a diagnosis in the accompanying video.

A 3-year-old boy is seen for unilateral swelling on the left side of the face, in front of and behind the left ear. Findings on examination of ears, oral cavity, and teeth are normal. He is afebrile (temp, 37°C [98.6°F]), cooperative, and in no distress. He is otherwise healthy. Past medical history includes 1 MMR vaccination.

After watching the video, which of the following confirms your diagnosis?