Definition:

Normal pressure hydrocephalus (NPH) is a progressive brain disease characterized by gait impairment, urinary incontinence, and dementia, and by ventricular enlargement in the absence of elevated intracranial pressure. NPH can be secondary to disease processes that cause inflammation of the arachnoid, such as subarachnoid hemorrhage, traumatic brain injury, or meningitis. As many as half of patients with NPH have no identifiable risk factor, and it is called idiopathic normal pressure hydrocephalus (INPH). Although INPH is usually considered an acquired form of hydrocephalus because the onset of symptoms is not until late in life, it has been reported that a subset of patients with INPH may actually have congenital hydrocephalus. Symptoms can be alleviated with a cerebrospinal fluid (CSF) shunt.