Dementia results from distortion of the periventricular limbic system. Hakim first described the mechanism by which a normal or high-normal CSF pressure exerts its effects. Pressure X Area, increased CSF pressure over an enlarged ependymal surface applies considerably more force against the brain than the same pressure in normal-sized ventricles. Normal pressure hydrocephalus may begin with a transient high-pressure hydrocephalus with subsequent ventricular enlargement. Intermittent intracranial hypertension has been noted in some patients.
Some authors prefer the term extraventricular obstructive hydrocephalus.
They believe that the initial event is diminished CSF absorption at the arachnoid villi. This obstruction to CSF flow leads to transient high-pressure hydrocephalus with subsequent ventricular enlargement. As the ventricles enlarge, CSF pressure returns to normal. Gait of NPH patients is bradykinetic, broad-based, and shuffling. Freezing episodes also can occur.