Normal pressure hydrocephalus - active and passive pathogenic mechanisms

Abstract

Normal pressure hydrocephalus (NPH) is characterized by normal CSF pressure, less than 18 cm H2O, classical clinical triad: gait disturbance, dementia and incontinence in patients with communicating hydrocephalus on CT or MRI. We analyzed retrospectively the NPH hospitalized patients in three neurosurgical departments between July 2007 and December 2012. Only the cases who met all diagnostic criteria were selected for this study. There were 47 selected cases of patients with NPH, including 24 patients with secondary NPH and 23 patients with idiopathic NPH. Ventriculo-peritoneal shunt was performed in all 24 patients with secondary NPH and at 11 patients with IdNPH. The short-term and long-term results were good and very good for cases of secondary NPH and good in 60% and poor in 40% in cases of IdNPH. The MR imaging showed the absence of CSF passage through the ventricular wall and the ventricular wall in cases of IdNPH with poor results after shunting: ependyma and glia limitans interna represents a fluid - parenchymal barrier between the brain parenchyma and the ventricles as a glialependymal barrier. We can consider that secondary NPH and some cases of idiopathic NPH with repeated small increases of ICP, with transependymal migration of CSF and hydrocephalus causing clinical triad because of the open glial-ependymal barrier, as an Active Normal Pressure Hydrocephalus and the shunt has good results. Other cases of IdNPH have not increases of intracranial pressure, no transependymal migration of CSF and there are periventricular deep lesions, without brain atrophy, causing clinical triad, as a passive hydrocephalus, it is a Passive Normal Pressure Hydrocephalus.