Figure 3c. Acute coalescent mastoiditis with a subperiosteal abscess in a 2-year-old girl with right acute otomastoiditis. (a, b) Axial CT scans of the temporal bone (a obtained inferior to b) show abnormal soft-tissue attenuation in the right mastoid air cells with erosion of the external cortex and sigmoid plate (arrows). Abnormal attenuation was also seen on the left side, which was probably due to serous otitis. (c) Axial contrast-enhanced cranial CT scan shows a subperiosteal abscess (arrow). No intracranial complications were identified.