E2700. What’s Hiding in Plain Sight: Differentiating Orbital Masses by Imaging Characteristics
  1. Alexis De La Cruz; University of Cincinnati
  2. Lily Wang; University of Cincinnati
Orbital lesions typically pose a diagnostic challenge for clinicians due to similar presenting symptoms and difficulty in obtaining biopsy tissue samples. However, prompt definitive treatment can significantly reduce morbidity and mortality. Thus, an accurate diagnose is critical to improve patient outcomes. Radiographic imaging of orbital masses plays an essential role in lesion characterization and aids in narrowing down the differential diagnosis. Orbital lesions are characterized radiographically by location as well as by specific imaging features on computed tomography (CT) and magnetic resonance imaging (MRI). An organized systematic approach to orbital mass evaluation can drastically improve accuracy of the radiologists’ differential.

Educational Goals / Teaching Points
Understanding and applying common imaging features associated with benign versus malignant lesions is an essential component to the systematic analysis of orbital lesions. Malignant lesions typically demonstrate rapid growth, osseous destruction, ill-defined margins, increased vascularity, and higher ADC mean values. CT is especially useful for characterizing orbital osseous destruction seen in many malignant lesions. MRI provides further characterization by demonstrating changes in signal intensity, unique enhancement patterns, vascular flow abnormalities, location (intraconal versus extraconal), extent of the lesion, and presence of optic nerve involvement. Furthermore, understanding pathognomonic imaging findings can further narrow the differential.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Determining the location of orbital masses is the radiologist's key to the correct diagnosis. Understanding and evaluating the orbital anatomy of the lesion is an essential tool to narrow down the differential. One of the first steps a radiologist should take in analyzing orbital lesions is assessing whether the lesion is preseptal or postseptal, followed by determining if the lesion is intraconal or extraconal. Postseptal lesions are then categorized as either intraconal or extraconal as divided by the extraocular muscle cone. The extraconal space consists of the orbital bone, subperiosteum, and the lacrimal fossa. The intraconal compartment consists of the globe of the eye, the optic nerve sheath complex , the retrobulbar space, and the orbital apex- cavernous sinus complex. Intraconal lesions are further divided by involvement of the optic nerve. Once location is determined, specific MR and CT characteristics of the lesions help narrow the differential further.

Orbital lesions are difficult to characterize clinically, are associated with high morbidity if left untreated and are typically difficult to biopsy. Prompt and accurate diagnoses can drastically improve patient outcomes. Radiologist should understand their key role in narrowing the differential and assisting in the diagnosis and treatment of orbital masses. Radiologists can use location of the lesion, key imaging features, and physical presentations to narrow the differential and aid in obtaining an accurate diagnosis and prompt definitive treatment.