Evaluation of periventricular hypodensity in adult hydrocephalus with CT cisternography and xenon-enhanced CT.

Metrizamide CT cisternography and Xenon-enhanced CT were employed to evaluate the periventricular hypodensity (PVH). CT cisternography was performed on adult cases with suspected communicating hydrocephalus, of which 43 cases showing ventricular reflux were investigated. In those cases in which significant transition of metrizamide into the area of PVH was followed after the ventricular reflux and stasis, the shunt operation was effective. The PVH disappeared post-operatively. However, in cases with PVH in which the metrizamide penetration did not occur, the PVH did not disappear post-operatively and clinical improvement was not detected. Xenon-enhanced CT was performed in six cases. Three cases exhibited communicating hydrocephalus, in which the area of PVH was not enhanced by metrizamide with CT cisternography. The other cases demonstrated acute high pressure hydrocephalus. The PVH in the former cases was neither enhanced by Xenon nor metrizamide, while the latter was enhanced significantly. Studies suggested that the reversible PVH was the result of an abnormally increased transition of cerebrospinal fluid through the ependymal layer, while the irreversible PVH resulted from the axonal destruction or demyelination of the periventricular white matter.