PETROUS BONE EXTENSION OF MIDDLE-EAR ACQUIRED CHOLESTEATOMA

Purpose: To describe CT and MR features of extension to the petrous bo ne, which is a rare complication of acquired cholesteatoma (AC). Mater ial and Methods: Postcontrast CT was performed in 4 patients, in axial (n = 4) and coronal planes (n = 2). The section thickness was 1.2 or 2.5 mm. MR was performed in 3 cases, using T1- and T2-weighted images (n = 3) and postcontrast T1-weighted images (n = 2). Results. CT demon strated a well-outlined lesion involving the petrous bone (n = 4). Den sity could be assessed in 3 cases, showing a hypodense unenhanced mass . Lateral (n = 1), superior (n = 2), and posterior (n = 2) semicircula r canals were affected in 3 patients. AC extended to the vestibula, co chlea, and internal acoustic meatus (IAM) in 3 patients. Two ACs exten ded to the level of IAM, whereas 2 extended further, to the petrous ap ex. Tn one case the sphenoid sinus was affected. On MR imaging the les ion was hypointense relative to brain on T1-weighted images and hyperi ntense on T2-weighted images. MR imaging helped to delineate the lesio n and to distinguish it from other cystic lesions of the petrous bone. Conclusion: CT and MR offer accurate preoperative assessment of the e xtension of cholesteatoma, which helps to choose the surgical approach .