Why does hydrocephalus progress?

Experimental results in rabbits support the hypothesis that occlusion of the cerebral subarachnoid space, resulting in an increased strain-stress ratio in the ventricular wall, is the mechanical basis of chronic progressive hydrocephalus within a rigid skull. When the cerebral subarachnoid space was drained through an artificial low-resistance fluid pathway, the wall of the olfactory ventricle showed edema that was indistinguishable from the edema of kaolin hydrocephalus. Increased CSF pressure did not produce edema of this grade when the cerebral subarachnoid space was patent. When the subarachnoid space surrounding the right olfactory bulb was occluded with silicone rubber, the right but not the left olfactory ventricle enlarged; resistance to cerebrospinal fluid absorption remained normal.