Multicompartmental Paranasal Sinus Osteoma Complicated by Frontal Bone Hyperostosis, Intracranial Mucocele, and Inflammatory Pseudotumor.

Parasinusal osteoma complicated by intracranial and orbit extension, cranial vault hyperostosis, intracranial mucocele, and inflammatory pseudotumor is exceptional. A 68-year-old man presented with a long history of progressive proptosis and recurrent episodes of keratoconjunctivitis in the left eye, with restriction in upward gaze. Contrast-enhanced magnetic resonance imaging revealed a frontal sinus lesion extending to the left anterior fossa and orbit, featuring an intracranial cystic component and heterogeneous contrast enhancement. Head computed tomography confirmed the double calcific-cystic nature of the lesion. A left supraorbital-pterional approach allowed complete resection of mucocele and drilling of intracranial and orbital osteoma, including the intrasinusal component. The frontal sinus was cranialized, and a flap of pericranium, reinforced by Gelfoam sponge, was reflected on the anterior cranial base/orbital roof. The postoperative course was uneventful; magnetic resonance imaging depicted resolution of proptosis. Histological examination favored parasinusal osteoma associated with intracranial mucocele, frontal bone hyperostosis, and inflammatory pseudotumor.