Macro- and microvascular changes, where both hypertension and diabetes are thought to play a role, with stiffening of the arterial walls and development of endothelial dysfunction in small vessels, causing increased permeability , could hypothetically contribute also to the disturbed hydrodynamics in iNPH, with increased CSF pulsations  and diminished perfusion in small vessels in the periventricular region [40, 41]. Shunting immediately changes the absorption mechanism and thereby “eliminates” both the vascular and hydrocephalic component of the disturbed CSF dynamics, as well as improves periventricular perfusion . As the effect of the shunt is permanent it may even compensate for the deterioration known to be associated with hypertension and diabetes and thereby explain the lack of negative long-term effects.