**1. Introduction**

Disorders of cognition have been identified since the beginning of the humankind, and since then, different types of clinical presentation have been reported. The same happened with the clinical manifestations of dementia.

Dementia is a neurodegenerative disorder characterized by a progressive decline in cognitive and functional abilities. This neurodegenerative process has multiple causes, clinical manifestations, and heterogeneity with respect to the impact of sex or gender on prevalence, risk factors, and outcomes [1–3].

In 2015, it was estimated that there were 46.8 million people with dementia worldwide, of whom 58.0% were living in low- and middle-income countries, and that there were annually 9 million new global cases of dementia.

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The estimated prevalence of dementia varies from 4.7% in Central Europe to 8.7% in North Africa/Middle East, and 6.4% at North America. Currently, the number of patients with dementia is projected to increase to 131.5 million by 2050 [4].

definitively confirm the diagnosis of various types of dementia and raise the accuracy of the diagnosis to 90%. A PET scan administered and reviewed by an expert delivers the most accurate and suggestive results while diagnosing dementia. The most accurate form of PET scanning for types of dementia is called stereotactic surface projection, which involves an

Updated Information on Some Cognitive Disorders http://dx.doi.org/10.5772/intechopen.81826 193

We did a bibliographic investigation, and then the PubMed, Embase, and Web of Science were searched. In this chapter, we comment about some types of dementia and cognitive impairment according to the available publications in the medical literature, and we also delivered some comments based on our clinical observation from working with affected patients in

The first man who made allusions to dementia at the seventh-century BC was the Greek philosopher Pythagoras (**Figure 1**) followed by Solon, Aristotle, Plato, Cicero, Galen, Celsus, Roger Bacon, and others. That related cognitive dysfunction with the aging on the brain is not well described until 1906, when Alois Alzheimer (**Figure 2**) found at postmortem brains of affected younger people, with dementia symptoms the microscopic plaques and tangles now

The concept of MCI is described in the nineteenth century when loss of recent memories was documented as the first sign of dementia [5]. Some degree of cognitive disturbance was thought to be part of normal aging, and then various names were used to define it such as (1) age-associated memory impairment, (2) age-associated cognitive decline, and (3) benign

In 1980, with the arrival of new neuropsychological test to measure subjective and objective cognition, an intermediate phase between normal aging and dementia became more widely accepted [8]. At that time, it was defined as the presence of subtle deficits in cognition with some impairment in executive function. Following an expert international conference, all previous definitions and the way of diagnosis and management of MCI were better performed [9, 10].

Historically, the term MCI has been in the literature for almost four decades, with the initial use coming from investigators at the New York University who referred to stage 3 on the

In 1999, some authors at the Mayo Clinic reported subjects in their community aging study presenting a memory problem beyond what was expected for age and who demonstrated a

The prevalence of MCI is estimated around 3–19% in the elderly people. However, in a com-

Conversion rates to dementia vary according to the setting, with 11–33% conversion over

MCI (by neuropsychological test) yet did not meet criteria for dementia [12].

munity setting, 44% of people with MCI returned to normal after 1 year [13].

Mthatha (one of the rural areas of South Africa) over the past21 years.

**2. Novel information on mild cognitive impairment**

advanced statistical analysis of the data.

known as hallmarks of the disease.

senescent forgetfulness [6, 7].

2 years [14].

Global Deterioration Scale as being MCI [11].

Apart from some neuropsychological test that we will describe at the end of this chapter, there are some radiological investigations that can help in increasing the certainty of dementia diagnosis. A positron emission tomography (PET) scan and a special form of MRI can more

**Figure 1.** Pythagoras of Samos (c 570 BC–c 495 BC).

**Figure 2.** Alois Alzheimer 1864–1915 from Bavaria.

definitively confirm the diagnosis of various types of dementia and raise the accuracy of the diagnosis to 90%. A PET scan administered and reviewed by an expert delivers the most accurate and suggestive results while diagnosing dementia. The most accurate form of PET scanning for types of dementia is called stereotactic surface projection, which involves an advanced statistical analysis of the data.

We did a bibliographic investigation, and then the PubMed, Embase, and Web of Science were searched. In this chapter, we comment about some types of dementia and cognitive impairment according to the available publications in the medical literature, and we also delivered some comments based on our clinical observation from working with affected patients in Mthatha (one of the rural areas of South Africa) over the past21 years.

The first man who made allusions to dementia at the seventh-century BC was the Greek philosopher Pythagoras (**Figure 1**) followed by Solon, Aristotle, Plato, Cicero, Galen, Celsus, Roger Bacon, and others. That related cognitive dysfunction with the aging on the brain is not well described until 1906, when Alois Alzheimer (**Figure 2**) found at postmortem brains of affected younger people, with dementia symptoms the microscopic plaques and tangles now known as hallmarks of the disease.
