Opacification of the middle ear and mastoid: imaging findings and clues to differential diagnosis.

Opacification of the middle ear and mastoid represents a spectrum of inflammatory, neoplastic, vascular, fibro-osseous, and traumatic changes. This article reviews the most important clinical and pathological characteristics, emphasizing CT and MRI findings. Knowledge of subtle patterns of middle ear and mastoid opacification at CT and MRI provide guidance towards the correct diagnosis.