Brain edema in delayed radiation necrosis: study of capillary ultrastructure--case report

A 42-year-old male was found to have cerebral radiation necrosis 2 years after a split course of radiation therapy following subtotal excision of a left parasagittal meningioma. The surgical specimens were studied by means of conventional ultrathin sectioning and freeze-fracture replication techniques. The electron density of the capillary endothelium was decreased, as was the degree of surface infolding. The width was irregular, and there was an unusually large number of pinocytotic vesicles (37/micron 2). The endothelium was also discontinuous, and the basal laminae were irregular in thickness. The pericapillary space was markedly enlarged, and accumulation of a fibrin-like substance was noted in the extravascular space. The pericapillary zone contained inflammatory cells. However, the tight junctions were preserved and the intercellular junctions were composed of five strands that appeared to consist of continuous particles. The authors conclude that activated pinocytotic vesicles play an important role in increasing vessel permeability in delayed cerebral radiation necrosis and that leakage may occur through interruptions in the endothelium.