The ultrastructural basis of periventricular edema: preliminary studies

The pathophysiology of periventricular lucency (PVL) on CT in primates was evaluated by transmission (TEM) and scanning electron microscopy (SEM). At 100 days after Silastic-induced hydrocephalus, six primate brains showed loss of cilia and ependymal cells over the ventricular surface and abnormal small supraependymal cells. TEM demonstrated communicating pathways between the ventricular lumen and brain parenchyma and the extracellular space was markedly increased. At 1000 days, ependymal changes in two brains were noted at greater distances from the ventricular angle. This study suggests that CT periventricular lucency in patients with hydrocephalus is due to the increased extracellular space. The lack of recognition of PVL by computed tomography in chronic normal pressure hydrocephalus may be due to change in distribution and resolution limits.