A Study Comparing Shunt Placement Versus Endoscopic Third Ventriculostomy in the Treatment of Hydrocephalus

The management of normal pressure hydrocephalus (NPH) is challenging due to diagnostic uncertainties and high treatment risks. To date, there are no evidence-based treatment standards for this disorder. Our long-term goal is to improve the outcome of NPH improving our understanding of cerebrospinal fluid (CSF) hydrodynamics. The Specific Aims are to 1) determine the value of a high volume tap test, and 2) determine whether intracranial hemo/hydrodynamic variables, measured before a shunt operation, support the tuned-dynamic absorber model of intracranial pressure dynamics. The study's Aim relates to modeling the complex hydro- and hemodynamics of intracranial physiology-pathology. We hypothesize that current hydrocephalus models are over-simplistic and that shunt-induced hydrodynamics are better modeled based on ICP waveform characteristics and the application of novel dynamic models. Much of the data for this Aim will be passively recorded during the routine care of the patient. In essence, we are only adding noninvasive MRI studies and TCD (transcranial Doppler) studies. The experimental methodology is aimed at altering the intracranial compartment compliance by placing the patient in various positions so that these phase differences can be detected. The simplest way to alter intracranial compliance is to make postural changes. When a patient is in the Trendelenburg position, venous outflow out of the brain is hindered resulting in an increase in ICP and presumably a reduction in compliance. Conversely, raising the head of bed to 60 degrees will result in the opposite effect. The second mechanism of altering compliance (and ICP) will occur as a result of treating the hydrocephalus with a CSF shunt. Because we are able to study hydrocephalus patients prior to shunting as part of their diagnostic workup, we create a new state with the shunt that will allow us to further characterize the intracranial system.