Disappearance of enhancement of brain tumor in contrast CT scan after excessively high dosage of dexamethasone

The method of steroid administration was studied as suggested by CT findings in 5 cases of brain tumor. In the CT image 72 hours after administration of dexamethasone 96 mg/d, contrast enhancement (CE) disappeared nearly completely in 3 cases of malignant glioma, and the indentification of tumor image on CT became difficult. Two cases of pinealoblastoma and low grade astrocytoma, respectively, showed only a little decrease of CE. From the CT images of 201 cases, the correlation between peritumoral edema and CE was that both were strong in glioblastoma, the former stronger in metastatic brain tumor, the latter stronger in meningioma, and both weak in low grade glioma and medulloblastoma. Steroid administration is indicated in tumors supposed to have little vascular pooling and strong extravascular accumulation of a contrast medium from the mechanism of CE in CT, and marked suppression of permeability with excessively high dosage seems to be noted as the change of CT findings. (J.P.N.)