This chapter presents the existing data concerning the epidemiology of selected forms of hydrocephalus, concentrating on congenital and infantile hydrocephalus and idiopathic and secondary normal pressure hydrocephalus (NPH). The epidemiology of congenital and infantile hydrocephalus has been explored in several studies. Casmiro et al. based the diagnosis on absence of known causes of secondary NPH, impaired gait, and CT scans showing findings indicative of NPH. The chapter explores the epidemiology of idiopathic normal pressure hydrocephalus (iNPH) in a Norwegian county of 220000 inhabitants, by actively informing the public and professional health workers about the condition, asking for referral of suspected individuals on a broad clinical basis. The lack of universally accepted guidelines for the diagnosis of iNPH, and the lack of powerful tests to predict shunt success, probably also contribute to the relative low rate of diagnosis, and consequently, of surgery.

The recent and rapid increase of the elderly population in developed nations has heightened the social importance of precise diagnosis and appropriate treatment for idiopathic normal pressure hydrocephalus (iNPH). This chapter reviews various assessment batteries that have been used in iNPH to date. There are many NPH assessing scales, most of which aim to assess level of general activity, severity of respective NPH symptoms, response to interventions such as cerebrospinal fluid (CSF) drainage tests or shunt surgery, and short and long term outcome. Comparative study of the specificity and sensitivity of the neuropsychological tests is necessary to determine the most reliable test for prediction of shunt surgery. The scale consists of the four domains of gait, neuropsychology, balance, and continence. The improvement of cognitive impairment was the major factor in reducing care-giver burden.

Structural and functional brain imaging have helped to elucidate the neural pathways involved in hydrocephalic cognitive impairment. In addition, studies of brain metabolism and blood flow, molecular imaging, and cerebrospinal fluid (CSF) physiology have provided novel windows into the pathogenesis of dementia in idiopathic normal pressure hydrocephalus (iNPH). A number of pathophysiologic mechanisms have been identified that are potentially relevant to the pathogenesis of the cognitive symptoms of iNPH, namely, mechanical distortion, pressure effects, and cerebrovascular compromise. A possible synthesis of these mechanisms would be that an imbalance of CSF production and clearance leads to progressive ventricular enlargement. The profile of cognitive impairments in iNPH is recognizably that of a subcortical pathological process. Deficiencies in attention, working memory, set shifting, response inhibition and other aspects of executive functioning are commonly observed in iNPH and can be seen early in the disease course.

This chapter attempts to develop biomarkers specific for idiopathic normal pressure hydrocephalus (iNPH) to distinguish it from other neurodegenerative conditions. The case for emerging biomarkers in iNPH has arisen because of similar developments in other common causes of dementia and the increasing awareness of both the epidemiology of NPH and its impact on the quality of life of elderly patients. Changes in the neurochemical composition of cerebrospinal fluid (CSF) due to hydrocephalus have been widely documented. The problem with identifying diagnostic biomarkers between NPH and Alzheimer's disease (AD) is that NPH was used in those studies more as a comparative control group rather than as the primary studied group, apart from a few exceptions. The difficulty in the differential diagnosis of PD with patients with NPH lies in the features of the gait disorder. There have been much fewer studies developing prognosis biomarkers when compared with those assessing diagnostic biomarkers.