Effects of dexamethasone on cerebral perfusion and water diffusion in patients with high-grade glioma.
OBJECTIVE
The mechanisms by which the glucocorticoid dexamethasone produces its therapeutic action in patients with intracranial tumors still remain unclear. The purpose of this study was to investigate whether dexamethasone affects cerebral perfusion and water molecule diffusion by using quantitative dynamic susceptibility contrast perfusion MR imaging (DSC-MR imaging) and diffusion tensor MR imaging (DT-MR imaging).


METHODS
Ten consecutive patients with glioblastoma multiforme underwent DSC-MR imaging and DT-MR imaging before and 48-72 hours after dexamethasone treatment (16 mg/day). Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and water mean diffusivity (<D>) were measured for enhancing tumor, nonenhancing peritumoral edematous brain, and normal-appearing contralateral white matter before and after steroid therapy. The percentage change in CBF, CBV, MTT, and <D> for the 3 tissue types was calculated for each patient, a mean value obtained for the population, and the statistical significance determined by using a paired-samples Student t test.


RESULTS
After dexamethasone treatment, there was no significant change in tumor CBF, CBV, or MTT. Edematous brain CBV and MTT were also unchanged. There was, however, an increase in edematous brain CBF (11.6%; P = .05). <D> was reduced in both enhancing tumor (-5.8%; P = .001) and edematous brain (-6.0%; P < .001). There was no significant change in CBF, CBV, MTT, or <D> for normal-appearing contralateral white matter after treatment.


CONCLUSIONS
These data suggest that dexamethasone does not significantly affect tumor blood flow but may, by reducing peritumoral water content and local tissue pressure, subtly increase perfusion in the edematous brain.
Department of Medical and Radiological Sciences, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom.
M E
ME
Bastin
T K
TK
Carpenter
P A
PA
Armitage
S
S
Sinha
J M
JM
Wardlaw
I R
IR
Whittle
D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity / Q000187:drug effects; D001810:Blood Volume / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects*; D001921:Brain / Q000098:blood supply*; D001929:Brain Edema / Q000175:diagnosis / Q000188:drug therapy; D001932:Brain Neoplasms / Q000098:blood supply* / Q000188:drug therapy; D003287:Contrast Media; D003907:Dexamethasone / Q000627:therapeutic use*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D019786:Gadolinium DTPA; D005909:Glioblastoma / Q000098:blood supply* / Q000188:drug therapy; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012039:Regional Blood Flow / Q000187:drug effects; D012680:Sensitivity and Specificity
D003287:Contrast Media; D003907:Dexamethasone; D019786:Gadolinium DTPA