Petrous Apex Lesions: Pictorial Review

Abstract

Received January 19, 2010; accepted after revision August 4, 2010. 1Department of Radiology, Division of Neuroradiology, University of Alabama at Birmingham Medical Center, 619 19th St S, WP-150, Birmingham, AL 35249-6830. Address correspondence to A. K. Bag (abag@uabmc.edu). 2Present address: Department of Radiology, Edward Hines Jr VA Hospital, Hines, IL. AJR 2011; 196:WS26–WS37 0361–803X/11/1963–WS1 © American Roentgen Ray Society Objective The petrous apex is a pyramidal shaped, variably pneumatized structure of the skull base that forms a unique intersection between the suprahyoid neck and the intracranial compartment. Given its location, the petrous apex is susceptible to multiple pathologic processes including intrinsic lesions of bone, pneumatized air cells, or the petrous internal carotid artery; invasive “downgoing” intracranial processes; or invasive “upgoing” infiltrating nasopharyngeal or sinonasal lesions. Clinical presentations of these lesions, therefore, can be quite variable and depend largely on involvement of numerous intimately adjacent intraand extracranial structures, especially the cranial nerves. Given this variability, petrous apex lesions cannot be diagnosed accurately on the basis of clinical findings alone. Fortunately, many of these lesions have characteristic MRI and CT appearances that can often allow a precise diagnosis. The purpose of this pictorial review is to emphasize these unique imaging features in association with focused clinical presentations and brief management outlines.