Presentation
Post assault with traumatic facial injuries.
Patient Data
Left black eyebrow sign after facial trauma. No overt orbital rim deformity or left maxillary opacity to suggest occult orbital rim fracture.
A paranasal sinus CT was recommended to assess for possible occult fracture.
Annotated facial bone CT for confirmation
Gas locules in the left superior orbit, consistent with black eyebrow sign.
Mildly displaced left lamina papyracea fracture with partial opacification of the middle ethmoid sinus by orbital fat. No evidence of optic nerve entrapment on this study.
Case Discussion
Black eyebrow sign, classically shown on facial bone radiographs, usually represents injury to the ethmoid (lamina papyracea) or maxillary components of the orbit.
Gas accumulation within the superior orbit results in the eyebrow appearance demonstrated in this case.
Facial bone CT is more sensitive and can also assist in assessment for radiographically occult injuries and possible complications of orbital fracture (such as orbital nerve entrapment).