Hydrocephalus associated with obliteration of the longitudinal sinus.

There are theoretically three possible causes of hydrocephalus; first, an excessive production of cerebrospinal fluid, secondly a block in its circulation and thirdly a defect in reabsorption of the fluid. The majority of cases belong to the second group, that is obstruction to the circulation, and examples of hydrocephalus due to a defect in reabsorption from the subarachnoid space via the pia-arachnoid villi are extremely rare (Potter, 1952; Russell, 1949). The purpose of this communication is to report two cases, one of a child dying at the age of 2 years in whom hydrocephalus was due apparently to complete organization of the longitudinal sinus over which a bony ridge had developed, and a second child with a history suggesting a cerebral sinus thrombosis, and in whom the development of a similar bony ridge suggested the same aetiology.