Effects of dexamethasone on peritumoural oedematous brain: a DT-MRI study.
OBJECTIVE
Glucocorticoids (dexamethasone) are thought to reduce peritumoural brain oedema by decreasing the permeability of neoplastic capillaries and/or enhancing the clearance of extracellular water. Diffusion tensor magnetic resonance imaging (DT-MRI) was used to measure the water diffusion parameters of oedematous and normal brain in a group of patients with intracranial tumours before and after steroid treatment.


METHODS
Fifteen patients with intracranial tumours (seven with high-grade glioma, four with metastatic carcinoma and four with meningioma) were examined before and 48-72 h after dexamethasone treatment (16 mg/day). The mean diffusivity (<D>) and fractional anisotropy (FA) were measured for oedematous brain and apparently normal contralateral white matter before and after steroid therapy.


RESULTS
In all three patient groups there was a significant decrease in <D> of oedematous brain after steroid treatment (p<0.01). There was no significant change in FA of oedematous brain after treatment in any of the three groups. There was also no significant change in either <D> or FA of apparently normal contralateral white matter after treatment.


CONCLUSIONS
These data indicate that dexamethasone produces a localised reduction in the magnitude of extracellular water molecule mobility, and hence water content, in peritumoural oedematous brain. Furthermore, the magnitude of these changes is similar for both intra- and extra-axial tumours.
Sinha
S
S
Neurosciences, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK.
Bastin
M E
ME
Wardlaw
J M
JM
Armitage
P A
PA
Whittle
I R
IR
D000328:Adult; D000368:Aged; D016880:Anisotropy; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use*; D001921:Brain / Q000187:drug effects / Q000473:pathology; D001929:Brain Edema / Q000175:diagnosis / Q000188:drug therapy*; D002199:Capillary Permeability / Q000187:drug effects; D003907:Dexamethasone / Q000627:therapeutic use*; D038524:Diffusion Magnetic Resonance Imaging; D045604:Extracellular Fluid / Q000187:drug effects; D005260:Female; D005909:Glioblastoma / Q000098:blood supply / Q000175:diagnosis / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008577:Meningeal Neoplasms / Q000098:blood supply / Q000175:diagnosis / Q000188:drug therapy*; D008579:Meningioma / Q000098:blood supply / Q000175:diagnosis / Q000188:drug therapy*; D008875:Middle Aged; D015173:Supratentorial Neoplasms / Q000098:blood supply / Q000175:diagnosis / Q000188:drug therapy* / Q000556:secondary; D016896:Treatment Outcome
D000893:Anti-Inflammatory Agents; D003907:Dexamethasone