Cerebrospinal fluid edema and its sequelae in hydrocephalus.

CSF edema is observed in the periventricular white matter in acute hydrocephalus especially when the intraventricular pressure is elevated; there is usually no detectable disturbance of the blood-brain barrier. Histological and ventricular perfusion studies suggest that CSF flows through the intact or disrupted ependyma into the periventricular white matter when the normal pathways of drainage are occluded. Absorption of fluid into the blood probably occurs through the periventricular blood vessels as an alternative pathway of CSF drainage. There is tissue damage in the edematous periventricular white matter and gliosis ensues. However, the degree of active tissue disruption is reduced in the chronic stages of hydrocephalus when the CSF edema is often reduced.