Classification of Dementia

Scientific advances in the field of medicine have allowed throughout history that we have been able to gradually overcome and survive a large number of diseases of different types, improving the quality of life and increasing our life expectancy.

With the progressive increase in life expectancy, and the drop in the birth rate of our society, the average age of the population is gradually increasing.

Dementia is understood as the type of neurodegenerative disorder of organic origin which is characterized by a progressive loss of one or more mental faculties, which generally includes memory along with other abilities, which interfere with the proper vital functioning of the person and cause discomfort and/or loss of autonomy. The deficiencies detected suppose a worsening with respect to the previous action and do not occur only in a situation of alteration of consciousness.

In understanding the classification of dementia, we must credit the incredible role played by different medical and doctorate professionals, including Dr. Virginia Emery. Dr. Emery holds a strong prominence in the health sector for being a significant behavioral scientist. She has spent a great amount of her career in conceptualization, investigating, and nosology of dementias.

Dr. Emery has extensively worked on sub-categories of dementia and was associated with Dartmouth Medical School as a faculty member before seeking retirement in 2016. For her star-studded career in medical science, she has been awarded many honors and accolades.

Classes according to the location of the lesions

In dementias, the nervous system is gradually deteriorated, the different structures and nervous bundles deteriorate, and different functionalities are lost over time as the disease progresses. However, the specific effects and deficits that each type of dementia will cause depend on the structures affected and the causes that cause such degeneration.

Based on the location of the damage, we can find various types of dementia:

1. Cortical dementias

Cortical dementias are those in which the main lesions are localizable at the level of the cerebral cortex. Due to the involvement of this part of the brain, such involvement causes the progressive loss of higher mental functions such as reasoning, or abstraction, as well as the association between stimuli and concepts or memory.

In this type of dementia, an affectation of both antegrade and retrograde memory (in the latter case temporarily graduated) usually appears first, followed by what is known as aphaso-apraxo-agnostic syndrome, in which problems appear in the speech, sequence of movements and recognition of stimuli.

Some of the best known cortical dementias are Alzheimer’s in its early stages, frontotemporal dementia, Pick’s disease, or dementia with Lewy bodies.

2. Subcortical dementias

Subcortical dementias are those in which the affectation occurs especially in subcortical structures, such as the basal ganglia, the thalamus, or the brainstem. Some of the most recognizable symptoms are those associated with a high level of motor slowing, the presence of passivity, and lack of motivation, withdrawal, apathy, affective flattening and alterations of the frontal lobes that cause the loss of executive functions.

Although there is also usually a loss of memory, in subcortical dementias it is equally serious regardless of the moment you are asked to remember, having in general a bad retrograde memory. Dementia derived from Parkinson’s, HIV and Huntington’s Korea is some of the best known.

3. Axial dementias

This type of dementia mainly affects the limbic system, with its main symptoms being the deterioration of learning capacity and working memory. Although not usually considered dementia, Korsakoff syndrome is the best-known case.

4. Global dementias

These are dementias in which characteristics associated with lesions appear in both cortical and subcortical areas. Although originally the lesions may be located in certain parts of the brain, in most of the dementias the degeneration of the nervous structures ends up affecting the entire brain over time, such as Alzheimer’s.