Early changes measured by magnetic resonance imaging in cerebral blood flow, blood volume, and blood-brain barrier permeability following dexamethasone treatment in patients with brain tumors

Object. In this study the authors assessed the early changes in brain tumor physiology associated with glucocorticoid administration. Glucocorticoids have a dramatic effect on symptoms in patients with brain tumors over a tim e scale ranging from minutes to a few hours. Previous studies have indicate d that glucocorticoids may act either by decreasing cerebral blood volume ( CBV) or blood-tumor barrier (BTB) permeability and thereby the degree of va sogenic edema. Methods. Using magnetic resonance (MR) imaging, the authors examined the ac ute changes in CBV, cerebral blood flow (CBF), and BTB permeability to gado linium-diethylenetriamine pentaacetic acid after administration of dexameth asone in six patients with brain tumors. In patients with acute decreases i n BTB permeability after dexamethasone administration, changes in the degre e of edema were assessed using the apparent diffusion coefficient of water. Conclusions. Dexamethasone was found to cause a dramatic decrease in BTB pe rmeability and regional CBV but no significant changes in CBF or the degree of edema. The authors found that MR imaging provides a powerful tool for i nvestigating the pathophysiological changes associated with the clinical ef fects of glucocorticoids.