[Cyst formation of meningioma: report of two cases and review of literature].

Cystic meningioma is rare and said to account for 1 to 2% of all types of meningioma. Here we report two cases of cystic meningioma. Case 1 is a 25-year-old man. He had suffered from sporadic epileptic seizure for about two years until the first CT was performed. It revealed a large cystic lesion at the right parietal region in touch with the midline structure. A nodular high density area was delineated in the contrast enhanced CT on the medial wall of the cyst. He showed no neurological abnormality at all. Case 2 is a 56-year-old female who had been complaining of memory disturbance, and an episode of sudden dizziness followed by a syncope that lasted for a few minutes. Neurological examination revealed slight right hemiparesis, right homonymous hemianopsia and left papilledema. A large cystic lesion was delineated at the temporal region in the plain CT, and no positively enhanced region could be found in the contrast enhanced CT. After surgical removal of the tumors, both cases were identified as cases of meningioma. They were diagnosed histopathologically as a fibroblastic meningioma and a meningotheliomatous meningioma respectively. The wall of the cyst consisted of the cortical surface per se in both cases. Preoperative diagnosis of such cases and the mechanism by which the cyst is formed were also discussed.