Communicating hydrocephalus is, by definition, a hydrocephalus in an individual whose CSF circulation pathways are competent from the ventricles inside of the brain to the fluid spaces just below the third ventricle, the so-called basilar cisterns. Classically it was thought to arise when the arachnoid villi became obstructed and were no longer able to transmit the CSF from the subarachnoid space investing the brain into the blood vessels draining the brain. Recent work by several pediatric neurosurgeons has suggested that there may be several causes for communicating hydrocephalus, with some being due to altered or compromised blood circulation within the brain, within the skull or within the chest. As these special causes become better understood, alternative treatments may become available. For now, though, the treatment for this condition is some form of a shunt.