Brain edema associated with brain tumour is one of the most important factor contributing to the morbidity and mortality associated with brain tumour. The major mechanism for edema formation within and around brain tumour is abnormal permeability of newly created microvessels in the growing tumour. It was found that endothelial proliferation is common in malignant gliomas and that new tumour vessels are derived from previously existing vessels. However, these newly formed vessels are often

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... tive. These defective vessels form an ineffective barrier and allow leakage of plasma exudates into the surrounding brain 1 . It is thought that enhancement of brain tumour by contrast media in CT and MRI is due to open interendothelial junctions, fenestrae, gap junctions and increased pinocytic vesicles in the capillaries of these tumours 2 . However, it is not known whether the putative defect, which governs the development of edema, is the same as one, which causes contrast enhancement. It is also not known whether these two factors are related to each other or how they are related to the degree of damage to the BBB. The present study is aimed finding association between the volume of peritumoural edema and the degree of contrast enhancement in MRI of diffusely infiltrating astrocytomas. Abstract: Background: The development of peritumoural edema and contrast enhancement of brain tumour is both thought to be due to breakdown of blood-brain barrier. However, the exact mechanisms by which these phenomena occur are not completely understood. Our purpose was to find association between the volume of peritumoural edema and the degree of contrast enhancement in MRI of diffusely infiltrating astrocytomas. Method: A total of 42 patients with intracranial astrocytomas diagnosed by MRI findings who underwent surgery with histopathology showing diffusely infiltrating astrocytomas were selected from the study population. The volume of peritumoural edema was measured and visual assessment of the degree of contrast enhancement was scored. Result: A highly significant association was found (p<0.001) between the volume of peritumoural edema and the degree of contrast enhancement. Conclusion: These results can be viewed as indirect, radiological evidence that edema production is quantitatively related to the degree of breakdown of the BBB as determined by the gadolinium enhancement.