[Normal pressure hydrocephalus. An evaluation 25 years following the initial description].

A quarter of a century after the first description of a condition known as "normal pressure hydrocephalus", there no longer exists serious doubt about the existence of this disease nor about the possibility of treating it surgically with success. Nevertheless, there is still no general agreement on the exact definition of this condition, nor is there confirmed knowledge regarding its pathogenesis. Approximately half of the cases still are designated "idiopathic" in as much as physicians have no clear concept of its etiology. Some progress has been reached concerning the indication for operation: the "resistance to outflow" of cerebrospinal fluid can be measured now exactly by fluid infusion tests and seems to be a valuable predictor of outcome after shunting procedures. Reviewing world literature of the past 25 years reveals: the most important symptom of normal pressure hydrocephalus is not dementia, but disturbances of gait. Patients suffering from dementia, but not from gait-disturbances, do not gain from cerebrospinal fluid shunting and do not need to be investigated by invasive diagnostic procedures. In patients who suffer from gait-disturbances with or without dementia, with or without urinary incontinence, and in whom computed tomography reveals enlargement of ventricles without pronounced cortical atrophy, there should be a measurement of intracranial pressure and of the resistance to cerebrospinal fluid outflow.