Ventricular size after shunting for idiopathic normal pressure hydrocephalus.

It has been presumed that idiopathic normal pressure hydrocephalus is due to obstruction. We visualized the ventricles in 19 patients subsequent to shunting. We found no consistent relationship between clinical improvement after shunting and reduction in ventricular size. This suggests that the positive effect of shunting in at least some instances is due to some other factor than reduced ventricular size.