Section 3 Hemodynamic

**57**

**Chapter 5**

**Abstract**

**1. Introduction**

**2. Epidemiology**

between 1.6 and 5.4% [11, 12].

**3. Pathophysiology**

Normal Pressure Hydrocephalus

Normal pressure hydrocephalus (NPH) is characterized by dilated ventricles and a combination of gait impairment, cognition impairment, and loss of urinary control (urgency and incontinence). The only effective treatment for NPH is a CSF shunt; however, only a small percentage of patients ever receive it. The features of gait impairment in patients with NPH are difficult to distinguish from patients of neurodegenerative disorders with motor involvement, such as parkinsonism or dementia with Lewy bodies. CT or MRI imaging is required for the diagnosis of idiopathic normal pressure hydrocephalus. An Evans ratio of more than 0.3 indicates large ventricles, and a ratio of more than 0.33 indicates very large ventricles, but is not specific for idiopathic normal pressure hydrocephalus. The international and Japanese guidelines support shunt surgery as effective treatment of idiopathic normal pressure hydrocephalus, as does the American Academy of Neurology practice guideline. There is a need to provide longitudinal care of patients with idiopathic normal pressure hydrocephalus after shunt surgery as all symptoms respond well to shunt surgery.

Normal-pressure hydrocephalus (NPH) is the earliest identified cause of dementia which can be potentially treated [1, 2]. NPH was described by Hakim and Adams in 1965, and the entity was characterized by gait disturbances, impaired cognition, and urinary incontinence that is associated with ventricular enlargement without rise in cerebrospinal fluid (CSF) pressure [3, 4]. NPH may be primary or idiopathic NPH (without known precipitating factors) or secondary (due to trauma, hemor-

The exact incidence and prevalence of INPH is difficult to determine; however, the incidence of INPH is between 1.8 and 2.2 cases per 1,000,000 individuals [8, 9]. In a door to door survey from two German villages, the 0.41% prevalence of NPH was reported [10]. In patients with dementia, the reported incidence of NPH ranges

There are two main mechanisms involved in the pathogenesis of NPH [13, 14], that is, increased venous resistance and altered production and absorption of CSF. Studies

*Ravish Rajiv Keni, Harsh Deora and Amit Agrawal*

**Keywords:** normal pressure hydrocephalus, shunts surgery

rhage, infection, mass lesions, or delayed aqueductal stenosis) [5–7].
