Communicating hydrocephalus. Cisternographic and neuropathologic studies.

Chronic communicating hydrocephalus was produced in adult dogs by injection of silastic into the subarachnoid space. Electron microscopy was used to verify the sequence of pathologic changes in the ventricular wall. The pathologic findings were correlated with cisternographic images and measurements of cerebrospinal fluid (CSF) pressure. Early in hydrocephalus, the CSF pressure was increased and cisternograms showed ventricular entry and clearing; the ependyma was stretched and fluid accumulated in subependymal regions. In animals with chronic hydrocephalus, the CSF pressure was normal and cisternograms disclosed radioactivity persisting in the ventricles. At this time the ependyma was severely damaged, the subependymal white matter showed enlargement of the extracellular space, and degenerative changes were present in axons and myelin sheaths.