Objectives: 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.
Conclusion: 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.
- DT-MRI, diffusion tensor magnetic resonance imaging
- DW, diffusion-weighted
- EP, echo-planar
- FA, fractional anisotropy
- FOV, field of view
- FSE, fast spin-echo
- GBM, glioblastoma multiforme
- ROI, region of interest
- SD, standard deviation
- brain tumours
- magnetic resonance imaging
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This work was funded by the Cunningham Trust.
Competing interests: none declared
SS and MEB authors contributed equally to this work.
IW was not involved in the review process.