Representative T2 weighted MR images of different grades of mastoiditis.

<p>(A) Grade 0 mastoiditis, < 5% of the mastoid air cell is opacified; (B) Grade 1 mastoiditis, 6–33% of the mastoid air cell is opacified; (C) Grade 2 mastoiditis, 34–67% of the mastoid air cell is opacified; (D) Grade 3 mastoiditis, 68–100% of the mastoid air cell is opacified. A high-signal intensity area (white arrow) is observed in mastoid air cells in the left ear; the mastoid air cells in the right ear appear normal.