SHORT REPORT

Effects of dexamethasone on peritumoural oedematous brain: a DT-MRI study

S Sinha¹, M E Bastin², J M Wardlaw¹, P A Armitage¹ and I R Whittle¹

¹ Clinical Neurosciences, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK
² Medical and Radiological Sciences (Medical Physics), University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK

Correspondence to:
Correspondence to:
Dr M E Bastin
Medical and Radiological Sciences (Medical Physics), University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK; meb{at}skull.dcn.ed.ac.uk

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.

Abbreviations: 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

Keywords: brain tumours; dexamethasone; diffusion; magnetic resonance imaging; tensor

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