Nontraumatic subperiosteal orbital hematoma secondary to frontal sinus mucocele: Case report.

Nontraumatic subperiosteal orbital hematoma (NTSOH) secondary to a paranasal sinus mucocele is rare and may be mistaken for an orbital abscess. A 40-year-old man presented with acute proptosis, periorbital pain, diplopia, and reduced vision in the right eye. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated a mass in the superior region of the right orbit and another mass in the right frontal sinus, hinting at NTSOH. An external approach to the frontal sinus combined with endoscopic sinus surgery (ESS) was performed for treatment. Intraoperative drainage of brown hemorrhagic fluid confirmed NTSOH associated with a frontal sinus mucocele. No recurrence of hemorrhage occurred during follow-up. This case highlights that NTSOH should be considered when an acute superior orbital mass coexists with a frontal sinus mucocele, particularly when MRI findings are compatible with evolving blood products.