Internal hydrocephalus.

Dandy and the pediatrician Blackfan published two papers on the production, circulation, and absorption of CSF in the brain and on the causes and potential treatments of hydrocephalus. Hydrocephalus is the buildup of CSF within the brain, an often lethal condition if left untreated. They described two forms of hydrocephalus, namely "obstructive" and "communicating," thus establishing a theoretical framework for the rational treatment of this condition.