Brain Herniation into Nasal Cavity Secondary to Large Convexity Meningioma

Acquired (nontraumatic) brain herniation through the ethmoid is rarely associated with an intracranial mass away from the anterior skull base. A 55-year-old diabetic woman presented with progressive frontal headache, anosmia, and blurred vision without rhinorrhea. Brain magnetic resonance imaging showed an intracranial tumor of the left frontal convexity associated with a herniation of the frontal brain (encephalocele) into the left nasal cavity. A computed tomography scan confirmed the anterior skull base defect. The intracranial tumor was totally excised after a left frontal craniotomy with a good outcome. Pathologic examination revealed a meningothelial meningioma. However, the patient and her family refused any surgery for the ethmoidal encephalocele. In our case report, this rare phenomenon (secondary nontraumatic encephalocele) probably occurred due to long-term increase of the intracranial pressure generated by the meningioma.