Pathogenesis of normal-pressure hydrocephalus--preliminary observations.

Eight cases with well-documented normal-pressure hydrocephalus were studied prospectively for 6 months by history, neurological examinations, Mini-Mental Status tests, xenon-contrast computed tomography measurements of local cerebral blood flow, and cerebral xenon solubility expressed as partition coefficients. Local cerebral blood flow and local partition coefficients were reduced throughout frontal and temporal lobes, basal ganglia, and thalamus. Cerebrospinal fluid shunting procedures were carried out in seven cases. As a result, local cerebral blood flow and local partition coefficients increased toward normal, particularly in frontal white matter, frontotemporal cortex, and basal ganglia. Ventricular size became reduced and mental status improved. Local partition coefficient values were reduced by increased tissue water because low values confirmed cerebrospinal fluid diffusion into white matter, which resolved after shunting. Patients likely to benefit from shunting, including shunt failures requiring revision, were detected.