Intradural extension of mucocele secondary to giant frontal sinus osteoma: Diagnostic pitfalls

Background: Paranasal sinus osteoma in association with intracranial mucocele is a rare entity while intradural extension is even rarer. Our aim of presenting this case is to highlight the diagnostic pitfalls and reiterate the importance of prompt treatment of expected complications. Case Description: A 35-year-old known epileptic, for the past 5 years, presented with altered sensorium for the past 2 days. Computed tomography (CT) of the brain plain showed ventriculomegaly and cystic lesion in the left frontal lobe adjacent to a calvarial osteoma. A ventriculoperitoneal (VP) shunt was done which resulted in tension pneumocephalus and led us to discover the origin of osteoma from the left frontal sinus on CT functional endoscopic sinus surgery (FESS) protocol. He underwent left frontal craniotomy. The osteoma and mucocele were excised completely and watertight primary dural closure was done. Postoperative meningitis was treated with antibiotics according to the culture report. Conclusion: Intracranial extension of mucocele led to meningitic hydrocephalus, prompting us for VP shunt. Resulting tension pneumocephalus revealed what was missed on preop CT, a small pocket of air adjacent to osteoma intracranially. Therefore, this case underscores the importance of obtaining a preoperative CT FESS to elaborate the origin of osteoma, thus planning approach differently.