Petrositis is an inflammation of the temporal bone, a bone in the skull that surrounds the ear. This inflammation goes deep to the inner ear. It is sometimes associated with otitis media (middle ear infection).
Chole RA, Sudhoff HH. Chronic otitis media, mastoiditis, and petrositis. In: Cummings CW, Flint PW, Haughey BH, Robbins KT, Thomas JR, eds. Otolaryngology: Head & Neck Surgery. 4th ed. Philadelphia, Pa: Mosby Elsevier; 2005: chap 133.