Radiosensitivity of meningioma--analysis of five cases of highly vascular meningioma treated by preoperative irradiation.

Preoperative 60Co-irradiation was given in five cases of highly vascular meningioma. Radiation doses ranged from 3,000 to 6,000 rads and were delivered over periods from 17 to 45 days. In one case of tentorial meningioma preoperative irradiation produced a marked reduction in the size and the vascularity of the tumour, as seen on the angiograms, and of the hot area in the brain scan. Papilloedema and abducens palsy also improved. After irradiation the tumour was totally removed. Histopathologically the tumour was a meningioma resembling a haemangiopericytoma. Coagulation necrosis of the parenchyma of the tumour was prominent. In the other four cases (three of meningothelioma type and one of haemangioblastoma type) the preoperative irradiation caused little or no change in the angiograms or in the brain scans. A mild clinical improvement occurred in one case, but deterioration took place in other cases. It may be concluded that preoperative irradiation gives little or no beneficial effect on meningiomas other than those of certain types, such as those resembling haemangiopericytomas, or malignant meningiomas. The clinical and radiological differential diagnosis between the usual types of meningioma and those which are either malignant or resemble haemangiopericytomas is discussed.