The conductance to outflow of CSF in adults with high-pressure hydrocephalus.

The intraventricular pressure was compared with conductance to outflow of CSF (Cout) in 12 patients with high-pressure hydrocephalus of less than 3 months duration. Cout was measured by a lumbo-ventricular or a ventriculo-ventricular perfusion test. In all patients Cout was very low (median 0.016 ml mm Hg-1 minute-1). Thus high-pressure hydrocephalus may be considered to be the consequence of a greatly increased resistance to resorption of CSF. The level of the measured ICP (mean: ICP 23.5 mm Hg) corresponded to the theoretical level calculated from the measured Cout. B-waves were observed during most of the recording periods and episodes of plateau waves were seen in all patients but one. In this particular group of patients, the unsatisfactory results of ventriculo-atrial shunting emphasize the high risks associated conditions leading to high-pressure hydrocephalus.