Giant air cells of the petrous apex: tomographic features.

Sixteen hundred consecutive tomographic examinations of the temporal bones were reviewed and 15 patients with petrous apical air cells larger than 1.5 cm diameter were encountered. Familiarity with the normal tracts of pneumatization, and precise localization of atypical air cells by tomography are helpful in differentiating deformity of the internal auditory canals due to asymmetric pneumatization from the change caused by acoustic neurilemmomas. Characteristic radiographic and CT features differentiate petrous apical air cells from other destructive lesions in the region.