Differences of cerebral circulation and glucose metabolism in the peritumorous edema between benign and malignant brain tumors

The regional cerebral blood flow (r-CBF) and glucose uptake rate in the edematous brain surrounding brain tumors which indicated a peritumorous low density area by X-ray CT, were studied in glioma (7 cases), and compared with meningioma (7 cases) by using bolus inhalation of 11CO: and oral administration of 11C glucose with positron emission tomography (PET; Headtome II). In low grade glioma and meningioma, r-CBF and g lucose uptake rate decreased maintaining good coupling between each other. Normalization of both decrease after total removal of the tumor was faster than the disappearance of the low density area shown by X-ray CT, on comparison with meningioma. In malignant glioma or recurrent glioma, however, there was no coupling between r-CBF and glucose up-take rate in the peritumorous low density area. The glucose uptake rate decreased markedly in association with either a decrease or increase in r-CBF. There was a difference in low uptake area between 11CO: and 11C glucose. These uncoupling changes between r-CBF and glucose uptake rate became more marked after total removal of the tumor, in spite of a tendency towards decrease of the low density area by X-ray CT. Based on these results, it became clear that the low density area surrounding malignant glioma by X-ray CT is not only simple edema due to increased local tissue pressure or mechanical stress like a meningioma, but a specific modification caused by vascularization or some products such as metabolic waste products from the malignant glioma. It is concluded that PET represents a useful tool for gaining information about the cerebral blood flow and metabolism in order to discriminate malignant glioma from low glioma, if the r-CBF and glucose uptake rate are studied in the peritumorous low density area by X-ray CT. (author)