Bicompartmental analysis of cerebrospinal fluid circulation

Abstract

✓ A new model for cerebrospinal fluid (CSF) circulation is proposed. Specific activity/time curves for CSF kinetics determined after intraventricular injection of a radiotracer were produced by fitting a biexponential function to data points and developing a two-compartmental model. Calculation of kinetic parameters of the model provides quantitative data about CSF dynamics. The study of each compartment separately and of the intercompartmental relationship is possible with this model. Sequential scan images and graphic plots of the variations of radioactivity in both compartments, derived from this model, add supplementary information in the evaluation of patients. Ventriculography was performed in 80 patients, who fell into four groups: those with normal CSF circulation, hydrocephalus, infantile hydrocephalus, and functioning ventricular shunts. Normal and hydrocephalic patients showed significant differences between the two groups in the means of some numerical parameters calculated from the new model. An increase of intraventricular radioactivity at 24 hours (p < 10−4) and of the volume of Compartment 1 (p < 0.01) with decreased volume of Compartment 2 (p < 10−4) and total flow outside the system (p < 10−3) were found in patients with hydrocephalus. The limiting values for normal patients were also estimated. Communicating and obstructive hydrocephalus could be differentiated by this method; however, no differences in mean values were found relating to the etiology or clinical course of the hydrocephalus. Normal-pressure hydrocephalus and cerebral atrophy produced significantly different mean values for the volume of Compartment 2 (p < 0.01), flow out of the system (p < 0.01), and intercompartmental flow (p < 0.01).