Cystic meningiomas.

Twenty-two cases of unusual intracranial meningioma associated with a cyst are reported and 144 published cases reviewed. The complex mechanisms leading to the formation of the cyst within the meningioma are analyzed on the basis of the surgical and histopathological evidence. The neuroradiological features (Computed Tomography and Angiography) which supply a correct preoperative diagnosis are discussed. It is clear from the literature how difficult preoperative diagnosis is, being possible only in 38% of cases with CT scanning and in 13% with angiography. It is necessary to remove not only the solid portion of the meningioma but also the cyst wall in order to prevent a recurrence. This is technically difficult for the type II intratumoural variety of Nauta's classification.