LAUSR

(e.g., cyst, tumor) can cause an “obstructive hydrocephalus” in which the reabsorption mechanisms are presumably intact, but bulk flow is blocked and the ventricles dilate proximal to the obstruction. In both variants, ventricular dilation is thought to be the end result of hydrostatic pressure build-up within the ventricles. Though perhaps intuitive, the preceding narrative of CSF physiology and pathophysiology is surprisingly thinly supported by empirical evidence. Furthermore, recent investigations, both in the realm of basic science using animal models and radiological sciences using advanced imaging techniques (e.g., cine phase-contrast MRI), have directly challenged many of the underlying assumptions of the classical dogma. Belgian scientist Georges LeMaitre, the physicist who first proposed the Big Bang theory, recognized that even a single experiment that yielded observations inconsistent with the fundamental claims of the theory risked invalidating the entire hypothesis [4] . At the very least, such an experiment would mandate a modification of the theory to account for the new and discordant observations. Only recently has the neurosurgical community begun to apply the same level of scientific rigor to the study of hydrocephalus. In a 2006 report by Bergsneider et al. [5] , the provocative and important question was posed: “...is there more to hydrocephalus than our long-held and oversimplified concept of it as a plumbing problem of mismatched CSF production and resorption...?” Asking questions and challenging old beliefs is only the first step. But it is the Introduction