[Inverted papilloma of the nose and paranasal sinuses with transdural intracerebral extension accompanied by brain abscess. Case report].

A 64-year-old male who had repeatedly undergone polypectomy for nasal polyps over a 20-year period was hospitalized with a “heavy feeling” in the head and disturbance of memory. Physical examination revealed the right nasal fossa to be almost completely blocked by a granular polyp. Neurological examination disclosed slightly impaired mental function, slight right exophthalmos, and bilateral papilledema. Skull X-rays revealed homogeneous clouding of the right nasal cavity and paranasal sinuses and an expansile lesion, resembling a mucocele, in the right frontal sinus. Computed tomography (CT) disclosed a soft-tissue mass in the right nasal cavity, paranasal sinuses, and orbit, with expansion of the right frontal sinus and destruction of the nasal septum, medial wall of the orbit, and roof of the frontal sinus. A patchy intracerebral mass with ring-like enhancement lay close to the expanded frontal sinus. Histological examination of the mass in the nose and paranasal sinuses showed typical inverted papilloma with a small malignant focus, and the diagnosis was squamous cell carcinoma. The intracerebral mass, which was also an inverted papilloma, was accompanied by a brain abscess and was not malignant. Intracranial extension is apparently a rare complication of inverted papilloma; only six such cases have been reported in the world literature. This appears to be the first reported case in which an inverted papilloma destroyed the dura mater and invaded the brain.