Acquired hydrocephalus. III. A pathophysiological study correlated with neuropathological findings and clinical manifestations.

On the basis of the laws of Pascal and Laplace, it is shown that the ventricular dilatation in acquired hydrocephalus is due to a primary increase in the intraventricular pressure (IVP), and that a new steady state can be reached, whether the IVP is increased or normal. The pressure increase is due to a disproportion between the production and reabsorption of cerebrospinal fluid (CSF). As water and salts pass freely across the ependyma and the choroid plexus in hydrocephalus, the pressure increase is caused by an increased protein concentration in the ventricular CSF, leading to increased fluid contents according to the Gibbs-Donnan equilibrium. During the ventricular dilatation, the ependyma is destroyed, and the protein molecules penetrate into the subependymal part of the white matter. This results in a reduction in the colloid osmotic pressure of the ventricular CSF, and a new steady state can be reached, with a normal protein concentration in an increased volume. The attendant microscopic changes in the ventricular wall were demonstrated in a patient with acquired hydrocephalus, and the observations made were in conformity with the results of a number of animal experiments. The symptomatology of acquired hydrocephalus is in agreement with a primary affection of the axons running in the juxtaventricular part of the white matter.