Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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September 14, 2017
Orbital Foreign Bodies
- Background:
- Identification of orbital foreign bodies can be difficult in the setting of acute trauma due to variable density of materials and differentiation from adjacent hemorrhage, gas, or bone.
- Orbital CT is the initial study of choice, as most foreign bodies can be identified and it remains safe in the presence of a metallic foreign body.
- MR with T1WI is more sensitive for detection of organic foreign bodies such as wood and should be considered if CT is negative and clinical suspicion remains high.
- Clinical Presentation:
- Ranges from severe acute trauma to more innocuous activities with significant delay before presentation
- Severe eye pain and/or pain with eye movements
- Blurry or decreased vision
- Globe injury or hemorrhage
- Periorbital edema and/or erythema
- Key Diagnostic Features:
- Wood will be low density with geographic margins and can occasionally be mistaken for gas within the orbit. Wood density is variable, with dry wood measuring around -650 HU and fresh/green wood measuring around -20 HU. Visualization is best using a wide bone or lung window setting.
- Plastic also has an extremely variable density, ranging from -125 to +365 HU.
- Metallic foreign bodies demonstrate beam hardening artifact and are usually easily detected.
- Differential Diagnoses:
- Surgically-placed hardware
- Orbital calcification
- Orbital gas in the case of low-density organic foreign bodies such as wood or some types of plastic
- Treatment:
- Treatment is variable depending on the foreign body material and location.
- Organic foreign bodies such as wood are typically removed and treated with broad spectrum antibiotics, as they can incite an intense inflammatory response and provide a source of infection.
- Small, metallic foreign bodies induce less of an inflammatory response and can be treated more conservatively in situations where removal would be difficult.
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