Computer analysis of periventricular lucency on the CT scan.

Of 53 patients with periventricular lucency, 70% revealed obstructive hydrocephalus, mainly due to infratentorial tumors, and the remainder were cases of communicating hydrocephalus, usually secondary to subarachnoid hemorrhage. Of the patients with PVL, 95% had hypertensive hydrocephalus and 60% showed slightly dilated ventricles. Computer analysis was helpful in displaying PVL objectively and clarifying its nature. In experimentally induced obstructive hydrocephalus, PVL was observed at the acute hypertensive stage. We concluded that the pathogenesis of PVL might be the passive diffusion or acute extravasation of CSF into white matter through the disrupted ventricular wall, rather than transependymal absorption of CSF.