Dementia Dementia is a non-specific syndrome that is characterized by a state of cognitive impairment and is often associated with memory, language, behavioral and motor disturbances. In general, a diagnosis of dementia requires that cognitive impairment is severe enough to affect an individual’s functioning in daily life. A global study estimated that, in 2010, the worldwide prevalence of dementia was 35.6 million people. This number is expected to double every 20 years . Dementia can be divided into both static and progressive forms. A static dementia can result from a wide variety of causes including brain injury, congenital defect or a toxic-metabolic/hypoxic event. Progressive etiologies of dementia are dominated by the neurodegenerative causes, especially in the older population. Mild cognitive impairment is distinguished from dementia by preserved functioning in daily life and often precedes neurodegenerative forms of dementia. Less common causes including infectious, autoimmune, paraneoplastic or toxic-metabolic often have a more subacute course. In this chapter, the major forms of neurodegenerative dementia syndromes will be detailed, along with the relevant clinical symptoms, diagnostic evaluation and neuroimaging. Alzheimer’s disease Alzheimer’s disease (AD) is the most common cause of dementia in the older population and thus has enormous individual, family and social consequences . The disease can be divided into two categories with respect to age of first clinical symptoms: early onset and late onset. Early onset, or symptoms beginning before the age of 60–65 years, represents 6–7% of all cases. The vast majority of AD cases present as late onset – at ages older than 60–65 years.
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