To demonstrate the Chandler Classification of orbital infections through illustrations and cross-sectional imaging To understand the anatomical basis of the Chandler classification of orbital infections To develop an appreciation of when imaging is indicated To understand the clinical implications of infections of the orbit

Introduction Infection of the periorbital region with or without the involvement of the orbit and beyond is not an infrequent indication for cross-sectional imaging encountered by radiologists. Infectious etiology has been quoted as accounting for over half of primary orbital pathology [1]. Clinical examination of the orbit and periorbit can be complicated by extensive soft tissue swelling necessitating cross-sectional imaging. A timely and appropriate diagnosis of orbital infection is key to preventing loss of sight and life.

Anatomical considerations Conceptualizing the orbit as a house, the walls of the orbit form a pyramidal-shaped space enclosed by the frontal, sphenoid, ethmoid, zygomatic, lacrimal, maxillary, and lacrimal bones [2]. Intimately related, the paranasal sinuses may act as a source of infection. While other paranasal sinuses may act as a nidus, the ethmoid sinus is most commonly accountable. Neurovascular perforations or dehiscence of the thin lamina papaya of the ethmoid bone account for this propensity [3,4]. [Fig 1] [Fig 2] Anteriorly the orbit is confined...

Infections of the orbit represent a serious risk of vision loss and mortality if managed incorrectly and therefore accurate radiological diagnosis is of key importance. Through a solid understanding of anatomy, pathophysiology, and classification, radiologists can contribute positively to the management of these patients.

1. Nagaraj UD, Koch BL. Imaging of orbital infectious and inflammatory disease in children. Pediatr Radiol. 2021 Jun;51(7):1149-1161. doi: 10.1007/s00247-020-04745-7. 2. Nguyen V, Singh A, Altmeyer W, Tantiwongkosi B. Demystifying Orbital Emergencies: A Pictorial Review. Radiographics. 2017;37(3):947-62. doi: 10.1148/rg.2017160119 3. Dankbaar JW, van Bemmel AJ, Pameijer FA. Imaging findings of the orbital and intracranial complications of acute bacterial rhinosinusitis. Insights Imaging. 2015 Oct;6(5):509-18. doi: 10.1007/s13244-015-0424-y. 4. Velayudhan V, Chaudhry ZA, Smoker WRK, Shinder R, Reede DL. Imaging of Intracranial and Orbital Complications of Sinusitis and...