CSF formation and absorption estimates by constant flow infusion method.

The constant-flow infusion method has been used to calculate conductance and the rate of CSF formation in 54 patients with varied but stable clinical pictures, normal CSF pressures, and dilated ventricles. Values for conductance varied from 0.00203 to 0.0263 mL/min/mm H2O, with a peak between 0.005 and 0.010, mL/min/mm H2O. Values for CSF formation uncorrected for a small, negative linear term containing the sagittal sinus pressure varied from 0.114 to 3.0 mL/min, with a peak between 0.5 and 1.0 mL/min, a range considerably larger than that given by earlier studies. Results indicate that CSF formation is reduced in the presence of low conductance. There is a possibility that the syndrome of normal pressure hydrocephalus results from underformation with ventricular stagnation. Low conductance values may identify shunt-responsive syndromes.