Small ethmoid mucocele with intracranial extension associated with fibrous dysplasia: A rare case report.

Ethmoid mucoceles are expansile, benign cystic lesions characterized by slow growth, predominantly affecting the frontal sinus, followed by the ethmoid sinus, and infrequently the sphenoid and maxillary sinuses. Intracranial involvement is rare and is typically associated with large or longstanding lesions. We present a case involving a 34-year-old immunocompetent woman who experienced non-specific facial pain subsequent to an influenza infection without exhibiting typical sinonasal or neurological symptoms. Computed tomography and magnetic resonance imaging revealed a small ethmoid sinus lesion (∼13-17 mm) with erosion of the anterior skull base and intracranial extension, resulting in mild compression of the frontal lobe without associated edema or neurological deficits. The patient underwent endoscopic sinus surgery, which resulted in complete drainage of the lesion. Histopathological analysis revealed the presence of coexisting fibrous dysplasia. The postoperative course was uneventful, with no evidence of complications or recurrence on follow-up examination. This case underscores that intracranial extension of an ethmoid sinus mucocele may occur even in small, clinically silent lesions, particularly in the presence of underlying bony abnormalities, such as fibrous dysplasia. Early multimodal imaging is crucial for diagnosis, and minimally invasive endoscopic management can yield favorable outcomes in appropriately selected patients.