E1356. Radiologic Approach to Evaluating Petrous Apex Lesions
  1. Raihan Noman; HCA Florida Oak Hill Hospital
  2. Seema Al-Shaikhli; Herbert Wertheim College of Medicine at Florida International University
  3. Thompson Antony; University of Florida Health
  4. Charif Sidani; Baptist Health South Florida
The petrous apex (PA) is a component of the skull base that lies anteromedial to the inner ear and internal acoustic canal at the medial portion of the temporal bone. It is closely linked to various crucial cranial structures, specifically cranial nerves VII/VIII, and the petrous portion of the internal carotid artery. The PA is prone to a wide range of pathology, both benign and malignant, that have a wide range of overlapping clinical presentations. Since the PA cannot be directly examined clinically but is clearly assessed with computed tomography (CT) and magnetic resonance imaging (MRI), the radiologist plays a vital role in evaluating pathology at the PA, categorizing the pathology as benign or malignant, and identifying the extent of disease. The purpose of this educational exhibit is to outline a simple approach for accurately categorizing pathology of the PA based on CT and MRI features.

Educational Goals / Teaching Points
Explore and outline the complex anatomy of the petrous apex and its adjacent vital structures. Propose a diagnostic algorithm for categorizing PA lesions into one of three main categories based on their CT and MRI features non-expansile, expansile non-aggressive, and expansile aggressive. Describe the classic imaging features of the most common PA pathology.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Origin of lesion is it intrinsic to the PA or extrinsic to PA? This can be assessed on CT and MRI. Type of lesion is it non-expansile, expansile non-aggressive, or expansile aggressive? This can be assessed on CT, which can delineate the osseous margins and matrix of the lesion. Lesion composition does it contain cerebrospinal fluid (CSF) or non-CSF? Is it solid or pretentious composition? This can be assessed with MRI. We will explore differences found on T1-weighted, T2-weighted, and fat-saturated T1-weighted images. Some key anatomic landmarks of the petrous apex that can help refine working differential diagnoses, petrous carotid canal (contains the internal carotid artery as it enters laterally and exits medially above the foramen lacerum), meckel cave (contains the trigeminal ganglion), dorello canal (contains the abducens nerve as it passes between the petrous apex and the petrosphenoidal ligament).

The petrous apex is a challenging area of the skull base for radiologists to interpret due to the complex anatomy and the diverse range of pathology that may affect it. As the neurosurgical management of skull base disorders has evolved, so too has diagnostic imaging. This educational exhibit provides an interactive overview of petrous apex lesions and how to evaluate them using CT and MRI.