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Neuroradiology Case of the Week

Case 354

October 2008

Daniel Ginat, MD, MS and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient 1 is a 91-year-old with orbital pain status post fall.
Patient 2 is a 45-year-old female with altered mental status.

Imaging Findings:
Patient 1: Combined left inferior and medial orbital wall blow-out fracture with associated ethmoid and maxillary sinus hematoma (Fig. 1). No herniation of orbital contents.
Patient 2: Incidentally encountered asymmetric deformity of the right lamina papyracea suggest an old, healed medial blow-out fracture (Fig. 2).

Diagnosis: Orbital Blow-Out Fractures

Discussion: Bony orbital trauma manifests as isolated or combined fractures of the inferior, medial, lateral walls of the orbit, orbital roof fractures, tripod fractures, nasal-ethmoidal-orbital fractures, and part of LeFort fractures [1]. Orbital bow-out fractures consist of orbital wall disruption with preservation of the orbital rim and result from increased intraorbital pressure from blunt trauma or may result from direct penetrating trauma. Although the medial wall is the thinnest portion of the orbit, the buttressing effects from the ethmoid bone make medial wall blow-out fractures less common than inferior orbital wall fractures. Indeed, the literature reports that the relative occurrence of inferior wall fractures is 72.5%, as opposed to 15% for isolated medial wall fractures [2]. Combined medial and inferior wall blow-out fractures constitute the remaining 12.5% [2].
     Orbital floor fractures are often associated with enophthalamos, diplopia, and ocular injury [1 & 3]. Isolated medial orbital wall fractures can be associated with orbital emphysema [1]. Intrasinus hematoma is very often seen in conjunction with medial wall fractures. However, medial rectus muscle entrapment is uncommon in these fractures despite the presence of intramuscular edema or hematoma. Orbital roof fractures may produce CSF leak, pneumocephalus, and intracranial injury [1].
      On plain film studies, maxillary sinus septum may be difficult to distinguish from inferior blow-out fractures [3]. Similarly, inferior wall orbital fractures may resemble “pseudo-blow-out” fractures, which actually involve fracture of the antrum wall. Yet another differential consideration on x-ray is the “blow-in” fracture, which results from anterior trauma to the maxillary sinus and is often associated with proptosis.
     The detail generated and scan rapidity make spiral CT is an optimal modality for evaluating suspected orbital fractures and their complications [4]. Although MRI is also sensitive in detecting orbital floor fractures, CT is superior to MRI in demonstrating small and associated fractures [5]. In particular, CT reformatted images in the coronal and sagittal planes facilitate detection of fractures and are invaluable to surgical planning [5].

References:

1. Mafee MF, Valvassori GE, Becker M. Imaging of the Head and Neck. 2nd ed., Thieme, New York, 2005.
2. Yano M, Tajima S. Isolated fracture of medial wall and floor of the orbit. Eur J Plast Surg (1994) 17:258-260.
3. Harris JH, Harris WH. The Radiology of Emergency Medicine, 4th Ed., Lippincott Williams & Wilkins, New York, 2000:.72.
4. Lee HJ, Jilani M, Frohman L, Baker S. CT of orbital trauma. Emerg Radiol. 2004 Feb;10(4):168-72. [PubMed]
5. Kousoubris PD, Rosman DA. Radiologic evaluation of lacrimal and orbital disease. Otolaryngol Clin North Am. 2006 Oct;39(5):865-93, vi. [PubMed]