Communicating hydrocephalus as a cause of aqueductal stenosis.

Eleven cases of presumed aqueductal stenosis with onset of symptoms after the first decade were reviewed. Ten patients had complete occlusion and one a high-grade stenosis. In 10, the dilated lateral ventricles caused a marked inferior displacement of the third ventricle. Postshunting diagnostic studies on six of these patients revealed ascent of the third ventricle, and in three of these the aqueduct was shown to be patent. It appears that in some cases of advanced communicating hydrocephalus the descending third ventricle kinks or pinches shut the aqueduct, adding an obstructive component which accelerates the clinical picture. The mechanism and clinical features of this process are discussed.