NORMAL-PRESSURE HYDROCEPHALUS - AN ANALYSIS OF ETIOLOGY AND RESPONSE TO SHUNTING BASED ON MATHEMATICAL-MODELING

The dynamics which maintain the state of enlarged cerebral ventricles and normal intracranial pressures (normal pressure hydrocephalus) are not completely understood, making the response to cerebrospinal fluid diversion difficult to predict. Using our previously described mathema tical model of intracranial physiology which allows nonlinear relation ships of pressure, volume, and flow in 7 distinct compartments, we des ired to determine factors which could be responsible for the developme nt and maintenance of the steady state of normal pressure hydrocephalu s. Using typical starting values for CSF volume, pressure, and flow, t he model indicates that this condition cannot be sustained, in spite o f high CSF outflow resistance, unless capillary flow resistance is ele vated. This condition can be the result of arterial hypertension. The additional modeling of a CSF diversion device demonstrates predicted t ime courses for ventricular size reduction which are consistent with c linical observations. We conclude that certain Vascular conditions may allow for the maintenance of an enlarged ventricular size, and that m athematical modeling can assist in identifying factors for clinical st udy that may maintain normal pressure hydrocephalus even after treatme nt by CSF diversion.