Corticosteroid therapy of experimental tumour oedema.

Experimental brain tumours were produced in cats by stereotactic implantation of 4 million suspended cells of a rat glioma clone into the internal capsule. Three weeks after implantation a spherical tumour developed with a diameter of up to 10 mm which was surrounded by vasogenic white matter oedema. In untreated animals water content in the peritumoural white matter increased form 69.1 +/- 0.9 to 80.0 +/0 0.8 ml/100 g w. w., and regional blood flow reciprocally decreased from 32.2 +/- 5.6 to 18.9 +/- 0.05 ml/100 g/min. A single injection of a crystalline suspension of 10 mg/kg dexamethasone given intramuscularly one week before the animals were killed, led to a significant amelioration of brain oedema. Peritumoural white matter water content decreased to 73.0 +/- 0.5 ml/100 g w w. and blood flow rose to 35.7 +/- 2.8 ml/100 g/min. These changes were accompanied by parallel shifts of electrolyte content buy did not correlate with EEG activity, as assessed by Fourier frequency analysis. Corticosteroids did not prevent extravasation of peroxidase or Evans blue across the tumour vessels. The beneficial effect, therefore, is attributed to either an acceleration of resorption or an inhibition of the spread of oedema from tumour into the peritumoural brain tissue.