Cystic meningioma presenting as a ring lesion.

A 56-year-old woman presented with a 2-year history of right hemispheric focal seizures confirmed by electroencephalography. Physical and neurologic examination revealed only a mild left-central facial nerve paresis. CT showed a cystic right parasagittal tumor with an enhancing wall (Fig. 1 A). The thin wall was of varied thickness but without focal nodularity. The cystic tumor abutted the falx broadly and displaced it slightly to the left . The cyst volume was measured at 32 cm , using the ellipsoid approximation . There was minimal edema surrounding the tumor. The CT density of the cystic part was slightly above CSF density. The CT findings were thought to be consistent with a slowly growing cystic tumor; astrocytoma was considered most likely . At surgery, a thin-walled cystic tumor with a firm periphery was found adherent to the fal x. A 20-ml sample of yellow-brown , highly proteinaceous fluid was aspirated. There was no evidence of necrosis or hemorrhage. The tumor was completely resected . The frozen section was interpreted as consistent with astrocytoma, but the permanent sections proved the tumor to be a meningioma (Fig . 1 B). There was no evidence of necrosis or malignancy. After surgery the patient 's facial paresis resolved and she has been well for the 2 years since her operation.