**1. Introduction**

Idiopathic normal pressure hydrocephalus (iNPH) was described for the first time in 1965 by Hakim and Adam as ventricular dilation accompanied by a progressive triad of a gait disturbance, "dementia" and incontinence. Usually gait and balance disorders appear early and are the most impressive symptoms, cognitive decline and incontinence generally appear later as the disease progresses [1].

The need for guidelines and operating criteria for the diagnosis and management of this condition was firstly implemented by the Japanese Society of Normal Pressure Hydrocephalus in 2004; as the paper however was available only in Japanese, in 2005 Marmarou et al. [7] published English language guidelines designed to be "acceptable in the United States and abroad". Then, as there were some differences between the two guidelines, International and Japanese, in 2008 Ishikawa et al. [8] proposed an English and up to date version of the previ-

Clinical and Cognitive Features of Idiopathic Normal Pressure Hydrocephalus

http://dx.doi.org/10.5772/intechopen.73273

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Finally, in 2012, given the significant increase in basic and clinical research on iNPH and the availability of more high level evidence, Mori et al. [9] published a revision of the English

More recently, Williams and Relkin [1] have published detailed indications on the diagnosis and management of iNPH; on the basis of an extremely clinical approach, the authors stress the concept that the starting point should be a comprehensive history and neurological examination, review of neuroimaging studies, and evaluation of the differential diagnosis. Moreover, the article reports a comparison between the International and Japanese Guidelines, where

In most cases of new onset of neurologic symptoms, a computerized tomography (CT) scan of the brain is initially obtained. Although magnetic resonance imaging (MRI) is more specific than CT in iNPH, a normal CT scan can exclude the diagnosis. As shown in **Figure 1** MRI

• ventricular enlargement out of proportion to sulcal atrophy, with typical rounding of fron-

• prominent periventricular hyperintensity consistent with transependymal flow of CSF

• aqueduct perviety (or slight enlargement) to exclude congenital stenosis. A more specific sign, prominent flow void in the aqueduct, the so-called hyperdynamic aqueduct or jet sign, requires spine-echo sequences, currently dismissed in routine MRI, replaced by the faster turbo-spinecho sequences, (Today, a confirmation of the hyperdynamic aqueduct should be obtained by measuring aqueduct cerebral spinal flow (CSF) stroke volume by phase-contrast MRI [10] • thinning and elevation of corpus callosum on the median sagittal slice, and acute callosal

A narrow CSF space at the high convexity/midline areas relative to Sylvian fissure size was recently shown to correlate with a diagnosis of probable or definite iNPH. This specific sign, called "Disproportionally enlarged Subarachnoid spaces Hydrocephalus" (DESH) [12] has been found the most sensitive to the ventricular shunting. To establish a diagnosis of NPH, an

angle in the coronal slice passing through the posterior commissure [11].

ous Japanese guidelines in order to make them known worldwide.

the former are more exhaustive regarding the clinical features.

language version of the Japanese guidelines.

**2. Imaging studies**

tal horns

and/or leukoaraiosis

findings in iNPH include the following:

The symptoms presented usually appear as:


The gait disturbance is typically the earliest feature noted and is considered to be the most responsive to treatment. The primary feature is thought to resemble an apraxia of gait or a "lower body parkinsonism". True weakness or ataxia is typically not observed. The severity of gait disorders range from mild to the wheelchair.

The urinary symptoms of NPH can present as urinary frequency, urgency, or incontinence. While incontinence can result from gait disturbance and dementia, in a study by Sakakibara and colleagues [2] 95% of patients had urodynamic parameters consistent with detrusor overactivity.

The cognitive and behavioral disturbances accompanying iNPH have been commonly described as "fronto-subcortical dysfunction".

However, this definition is reductive not encompassing the entire cognitive spectrum of iNPH deficits. We will deal with this topic more in detail later on.

The incidence of iNPH is between 2 and 6% among people affected by any dementia condition; its occurrence is probably underestimated. Brean and Eide [3] reported a prevalence of 21.9/100,000 and an incidence of 5.5/100,000 in a Norwegian population, which are probably minimum estimates according to the authors.

A more recent epidemiological study [4] confirms this impression: the prevalence of probable iNPH has been reported to be 0.2% in subjects aged 70–79 years and 5.9% in those aged 80 years and older, respectively, without difference between men and women. Moreover, as the authors wrote: "the number of subjects with iNPH is probably much higher than the number of persons currently treated", and since the prevalence increases with increasing age they estimate approximately that 2 million persons in Europe and 700,000 in the United States may have iNPH.

A high incidence was also reported by Iseki et al. [5] in a 10-year follow-up study of a population of 70 year olds from a rural Japanese community. A recent systematic epidemiological review [6] confirmed that this pathology is under-diagnosed.

The need for guidelines and operating criteria for the diagnosis and management of this condition was firstly implemented by the Japanese Society of Normal Pressure Hydrocephalus in 2004; as the paper however was available only in Japanese, in 2005 Marmarou et al. [7] published English language guidelines designed to be "acceptable in the United States and abroad". Then, as there were some differences between the two guidelines, International and Japanese, in 2008 Ishikawa et al. [8] proposed an English and up to date version of the previous Japanese guidelines in order to make them known worldwide.

Finally, in 2012, given the significant increase in basic and clinical research on iNPH and the availability of more high level evidence, Mori et al. [9] published a revision of the English language version of the Japanese guidelines.

More recently, Williams and Relkin [1] have published detailed indications on the diagnosis and management of iNPH; on the basis of an extremely clinical approach, the authors stress the concept that the starting point should be a comprehensive history and neurological examination, review of neuroimaging studies, and evaluation of the differential diagnosis. Moreover, the article reports a comparison between the International and Japanese Guidelines, where the former are more exhaustive regarding the clinical features.
