Normal pressure hydrocephalus (NPH) refers to a condition of pathologically enlarged ventricular size with normal opening pressures on lumbar puncture. NPH is distinguished from obstructive or noncommunicating hydrocephalus, in which there is a structural blockage of the cerebrospinal fluid (CSF) circulation within the ventricular system (eg, stenosis of aqueduct of Sylvius).
NPH is associated with a classic triad of dementia, gait disturbance, and urinary incontinence. Because this clinical syndrome is potentially reversible by the placement of a ventriculoperitoneal shunt, it is important to recognize and accurately diagnose. However, there is little consensus regarding the diagnosis of NPH and the selection of patients for shunt placement .
This topic provides an overview of the epidemiology, clinical features, diagnosis, and management of NPH. Other dementia syndromes are presented elsewhere. (See "Clinical features and diagnosis of dementia with Lewy bodies" and "Etiology, clinical manifestations, and diagnosis of vascular dementia" and "Clinical features and diagnosis of Alzheimer disease" and "Frontotemporal dementia: Clinical features and diagnosis".)
The incidence of normal pressure hydrocephalus (NPH) has varied in different studies from 2 to 20 per million per year [1-3]. These discrepancies probably reflect inconsistent definitions of NPH as well as differences among populations sampled.
NPH occurs as an idiopathic or secondary condition in roughly equal proportions . When associated with an identified etiology, NPH can occur in all age groups. In comparison, idiopathic NPH is most common in adults over the age of 60 years [5,6]. It is equally common in both sexes .