Idiopathic Normal Pressure Hydrocephalus (INPH) is a brain disorder characterized by the enlargement of the brain ventricular system while the cerebrospinal fluid (CSF) pressure remains within the normal range. INPH mainly affects men over 65 years of age: it is a progressive, chronic disorder, causing cognitive impairment, without a specific identifiable cause [1]. The idiopathic form must be distinguished from other chronic forms of hydrocephalus conditions, which can derive from brain surgery, meningitis, or head injury in 50% of cases [2].
INPH is characterized by ventricular enlargement without intracranial hypertension which expresses clinically gait disturbances, urinary incontinence, and dementia (known as the “Adams triad”), and accounts for 2–10% of all forms of dementia and 40% of adulthood hydrocephalus.
The classic triad appears like other neurological conditions, such as Alzheimer Dementia (AD) [1]. However, while dementia is not reversible, INPH dementia can be treated through neurosurgical procedures, by installing a shunt to drain excess CSF into another part of the body: this treatment may reverse the symptoms and restore the normal hydrocephalus functioning [3].
In fact, after treatment, clinical improvements have been reported in 30–96% of patients [4]. It was found that 93% of patients have gait improvements and more than 50% have significant cognitive improvements [5, 6].
Despite the large amount of data available, some aspects concerning the differential diagnosis between other forms of dementia and the accuracy of patients’ selection for ventriculo-peritoneal shunt are still controversial [7].
INPH is a real challenge for the medical community [8]: it is extremely difficult to differentiate INPH and AD based on the neurological deficits and/or considering clinical evidence only, as measuring ventricular size through conventional medical imaging techniques [9]. The distinction is clinically important because INPH, as it has been said, is one of the few treatable causes of dementia [10].
Hence, the main costs of INPH derive from the lack of diagnosis of the disease: the estimated annual cost for patients not treated due to a lack of diagnosis is € 1.695mln. Moreover, since there is no formal definition of INPH, this circumstance causes discrepancy in estimating its real incidence, that is thought to range from 2 to 20 per million/people per year. The difficulty of distinguishing INPH from other neurodegenerative disorders is the likely reason why about 80% of cases remain unrecognized and untreated [11]. Although data report 5/100,000 new cases diagnosed every year, the real number of people with INPH is supposed to be higher. A percentage ranging from 9 to 14% of the elderly living at home present INPH symptoms and a further increase in the number of people suffering from this disease can be assumed considering population aging [12].
An accurate diagnosis is necessary because conventional hydrocephalus treatments have no benefit in the non-hydrocephalus patients: if non-hydrocephalic patients are misdiagnosed as hydrocephalic patients, treatment have been shown not only to be ineffective, but are associated with significant morbidity and likely increasing costs [13].
In the light of these considerations, since the overall prevalence of dementia rises progressively as the population ages, even if INPH is responsible for only a small proportion of senile dementia, successful treatment could help many patients [14]. They could be treated in a short time with savings of resources; costs due to wrong therapies or inappropriate diagnostic procedures would be lower and patients’ quality of life would be higher.
About the type of treatment and assistance, the spontaneous course of INPH requires, for most patients, to rely on nursing care [15]. For those patients undergoing surgery, continuous and regular checks by the neurosurgeon are required, to ensure that the shunt is working properly [16]; continuous follow up and assistance can be complemented with physiotherapy treatments, socialization and psychological support.
A comprehensive estimation of INPH costs has not been performed so far: in 2000, hence, more than two decades ago, the costs of treating INPH, in the US, exceeded $1 billion: there were 27,870 patients with INPH treated, and more than 8,000 were new cases diagnosed; however, updates should be necessary [17].
Together with considerations of costs, another field of analysis is the implementation of new diagnostic tools. To our knowledge, no clinical or neuroradiological techniques have been validated to clearly identify dementia from INPH, as both share anatomical and clinical similarities [18]. Magnetic resonance imaging (MRI) depicts ventricle size accurately: however, findings on brain images are not sufficient, on their own, to establish a diagnosis because they provide minimal, if any, evidence of brain damage, despite marked deficits in motor skills and cognitive functioning [10, 19, 20].
In a study describing advantages and drawbacks of MRI parameters it has been stressed the importance to find specific imaging biomarkers likely to distinguish the two conditions [21]. If a screening tool may identify possible cases, then further workup could be done to confirm the diagnosis and determine the need for shunting [22–24].
The Rorschach test is usually considered in psychological diagnosis, clinical, personality assessment and selection context for the detection of the global personality profile in the pattern of response [25–29]. The response process of inkblot is centered on the identification of the mental function, cognitive pattern and characteristic traits of the personality [30, 31]. The answers to the questions posed through the perceptual task could get pattern of cognition, also visual-perception, language process or inhibition of the phases of the response process [32–35].
Despite the pioneering nature of the present study, its results have to be appreciated and carefully considered, since they allow to identify the common traits and pattern of response to INPH patients and AD.
Hence, this study is aimed at assessing the Rorschach method as a valid tool to recognize INPH patients. The information collected by administering the test have been analyzed through the implementation of three different methods: Population, Self-Organizing Maps (SOM), Artificial Neural Networks (ANNs). Characteristics of INPH vs. AD patients have then been outlined and commented. Some comments on the advantages of adopting the Rorschach test in such a complex diagnosis will conclude the study.