Cystic falx meningioma: report of a case with difficulty in radiologic diagnosis]

A case of cystic falx meningioma in the frontal region in which preoperative neuroradiologic diagnosis was difficult is reported. This 33-year-old man had suffered from epileptic seizures three times in one month. Physical and neurological examinations on admission were normal. A cystic mass with a small nodule was found on CT in the frontal region. Thin wall was enhanced smoothly and the nodule attached to the falx was enhanced heterogeneously. The mass was considered to be an extra-axial lesion on MRI. The right anterior falcine artery seemed to feed the mass. Bifrontal craniotomy was performed. Cyst was evacuated, and a soft reddish mass was subtotally removed. Cyst fluid was yellowish and protein content was 3.5 g/dl. Histopathological diagnosis was a meningotheliomatous meningioma and tumor cells were present also in the thin cyst wall. At the second operation the mass was completely removed, cyst wall inclusive. When we encounter a cystic mass in the sites of predilection of meningiomas, we have to consider the possibility of a cystic meningioma. If the mass has meningeal vascularization, a correct diagnosis is not difficult. Taking the location of the mass into consideration, an accurate interpretation of CT and MRI findings indicating extra-axial nature of the mass is indispensable.