Meningioma-associated brain oedema: the role of angiogenic factors and pial blood supply.

Abstract

Approximately 60% of meningiomas are associated with perilesional brain oedema. Several aspects have been evaluated in order to understand the pathophysiological mechanisms of oedema (age, sex of the patient, size and location of the tumour, histotype, grading), although at present they have yet to be completely clarified. We focused on pial blood supply, microvascular density (MVD) and angiogenic growth factors (i.e. vascular endothelial growth factor--VEGF) in order to evaluate their putative role in the development of brain oedema. We retrospectively studied 55 patients with intracranial meningiomas. Computerized tomography (CT) and angiographic studies were obtained in all cases. The angiograms provided an accurate differentiation between pial and dural blood supply, concomitantly with its semi-quantitative evaluation. The location and the volume of oedema, in relation to the meningioma surface, was evaluated using CT scans, as an oedema index (E/I). We also determined the expression of VEGF and MVD using standard immunohistochemical methods. Thirty-two out of 55 meningiomas presented peritumoural oedema, with an angiographic blush ranging from 2 to 4; VEGF protein was expressed in 27 out of 32 cases, independent of grade or histotype of tumours. In all patients, MVD ranged from 4 to 33.3 vessels (median value: 10.6). A significant relationship was found between the expression of VEGF and MVD (p = 0.0003) and between VEGF and E/I (p = 0.0023). Moreover, the E/I ratio was related to the blush (p = 0.0005). A significant association was also present between VEGF expression and pial blush (p = 0.0001). Our data confirm the central role of VEGF and pial blood supply in the pathogenesis of peritumoural oedema and support the hypothesis that the development of oedema in meningioma is vasogenic in type.