Types of dementias: the 8 forms of loss of cognition

Scientific advances in the field of medicine have allowed throughout history that little by little we have been able to go overcoming and surviving a large number of diseases of different types, improving the quality of life and increasing our hope of life.

However, there are still diseases, there are a large number of diseases and disorders that continue to pose a serious problem for our health and survival. Some of the major diseases to combat today are cancer, AIDS or the type of disorders to which this article is dedicated: the different types of dementias.

The concept of dementia

With the progressive increase in life expectancy and the decline in the birth rate typical of our society, the average age of the population is gradually increasing. Thus, little by little, a growing increase in the aging of the population is being seen, therefore some of the age-related or aggravated disorders. Among them are dementias.

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 usually includes memory together with other capacities, which interfere with the correct vital functioning of the person and cause discomfort and / or loss of autonomy. The deficiencies detected represent a worsening with respect to the previous performance and do not only occur in a situation of alteration of consciousness.

Is about a type of chronic, progressive, and irreversible disorder (Although in some cases the degenerative process may stop and even have a complete or partial recovery, such as those caused by hydrocephalus, poisoning or infections), produced by alterations in the body linked to a disease, substance use or deterioration and / or degeneration of brain processes usual. In addition, its effects may vary depending on the memory types those who affect the most.

• Related article: "Mild Cognitive Impairment (MCI)"

Classes according to the location of the lesions

In dementias the nervous system is deteriorated little by little, deteriorating the different structures and nervous bundles and, over time, different functionalities depending on the disease get moving. However, the specific effects and deficits that each type of dementia will cause depend on the structures affected and the causes that cause said degeneration.

Based on the location of the damage, we can find different types of dementia.

1. Cortical dementias

Cortical dementias are those in which the main lesions are located at the level of the cerebral cortex. Due to the involvement of this part of the brain in information processing and deep work at the information processing level, said affectation produces 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 both antegrade and retrograde memory impairment usually appears first (in the latter case temporarily graduated) followed by what is known as syndrome aphaso-apraxo-agnostic, in which there are problems in speech, movement sequencing, and recognition of stimuli.

Some of the best known cortical dementias are Alzeheimer in its initial stages, frontotemporal dementias, Pick's disease or dementia with Lewy bodies.

2. Subcortical dementias

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

Although there is also often memory loss, in subcortical dementias this is just as serious regardless of when you are asked to remember, generally having a poor memory retrograde. Parkinson's dementia, HIV, and Huntington's chorea are some of the best known.

3. Axial dementias

This type of dementia mainly affects the limbic system, its main symptoms being impaired learning ability and working memory. While not usually considered dementia, Korsakoff syndrome it is the best known case.

4. Global dementias

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

Main types of dementias

Regardless of its neuroanatomic location, some of the main types of dementias are as follows.

1. Alzheimer disease

The best known and most common of the dementias, Alzheimer's disease, is a dementia of cortical origin (although it ends up being cortico-subcortical) of insidious origin and slow progress that begins in the Parieto-temporal area of ​​the brain, with a progressive advance towards the frontal and the rest of the brain.

The cause of this disease is still unknown today, although it is observed in the brains of those who suffer from it. a high number of neurofibrillary tangles and beta-amyloid plaques.

There are usually three distinct phases. The first symptoms are usually recent memory impairment, along with anterograde amnesia. A slight anomie and impoverished language appear. Other alterations also appear such as loss of olfactory ability, loss of interest and motivation, rigid behavior and irritability. In this phase there is frequent emotional suffering and even depression, since there is usually awareness of the disease. Still he is capable of being autonomous.

In a second phase, greater difficulties begin to appear since it is at this time that the aphasic-apraxo-agnosic syndrome usually appears. Cognitive abilities deteriorate to a great extent, with retrograde amnesia and a high level of disorientation. In this state the individual is no longer capable of leading an autonomous life, requiring constant supervision.

In the last phase, the subject is already able to recognize neither significant people nor himself, losing language until reaching silence and the basic skills of daily life. Over time he also loses motor skills, until he reaches permanent bedwetting.

2. Frontotemporal

Frontotemporal dementias are a subgroup of dementias also called taupathies (since there are alterations in tau protein) characterized in that the main involvement occurs in the frontal and temporal lobes, resulting in great alterations in personality and in the area of ​​language.

There are three variants, the frontal one characterized by changes in personality and behavior, dementia semantics in which the loss of meaning of words stands out without changing other aspects of the language and the aphasia progressive primary school in which difficulties appear in all areas of language.

3. Lewy Body Dementia

The most visible symptoms of this cortical dementia are serious problems with attention and executive functions, presenting aphasic-apraxo-agnosic syndrome, parkinsonian-type motor symptoms and hallucinations and delusions. Of progressive start and fast course, intense psychotic symptoms and disorientation are very common, as well as sudden loss of consciousness.

The structures known as Lewy bodies usually appear in most of the cerebral cortex, along with a deficit of dopamine.

4. Due to prion disease or Creutzfeldt-Jakob disease

It is a dementia caused by the transmission of prions, proteins without nucleic acid that infect the nervous system. They cause sudden and rapid dementia, with motor problems such as tremors and spasms and abnormal functioning of neurons.

5. For Parkinson's disease

Parkinson's disease is a neurological disorder in which the subcortical structures, especially the basal ganglia and the substantia nigra (and especially the nigrostriatal pathway) degenerate progressively. In these areas a high prevalence of Lewy bodies can be observed.

This degeneration is produced by a deficit in the functioning of dopamine, the most characteristic symptoms being the appearance of parkinsonian tremors that are produced especially in a state of revision. Likewise, there are difficulties in walking, motor slowing down, stooped posture, poor movement and facial expressionlessness.

The dementia associated with this disease, of the subcortical type, does not appear in all cases, although as the number of years increases from the onset of symptoms, its appearance is more likely. Typical symptoms of this dementia are slowing down both physically and mentally, along with high passivity.

6. By Huntington's Korea

Huntington's chorea is an autosomal dominant genetic disorder of full penetrance that affects neurons governed by the neurotransmitter in a particularly virulent way GABA and acetylcholine from the basal ganglia.

With a slow and progressive onset, in this neurodegenerative disease, constant uncontrolled movements appear, in the form of twists and twists of the parts of the body that are reminiscent of a dance.

The demential process, of a subcortical type, usually begins with behavioral and personality changes along with marked memory impairment, also appearing with time an affectation in the frontal lobe that leads to a progressive loss of executive functions such as planning and sequencing.

7. Dementia due to HIV

HIV infection, after several years of evolution, can end up causing in some cases the degeneration of multiple brain structures and pathways, causing a specific type of dementia known as associated dementia complex to HIV.

This type of dementia classified as subcortical is characterized by the presence of slowing down, problems readers, loss of spontaneity and hallucinations, decreased tracking movements and impaired movement in general. Usually progresses rapidly to severe dementia leading to the death of the patient.

8. Vascular or multi-infarct dementia

This type of dementia is caused by the presence of cerebrovascular accidents, either in the form of hemorrhage or stroke, affecting one or more parts of the brain. The effects can vary enormously depending on the affected area, producing a deterioration in some functions such as memory or language.

It is a type of dementia that, unlike most, It starts suddenly and abruptly, the patient generally noticing the change in state and physical or mental abilities. It is common for the deterioration produced to occur in a staggered manner, with also some periods of partial recovery.

Bibliographic references:

• American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders. Fifth edition. DSM-V. Masson, Barcelona.

• Santos, J.L.; García, L.I.; Calderón, M.A.; Sanz, L.J.; de los Ríos, P.; Izquierdo, S.; Roman, P.; Hernangómez, L.; Navas, E.; Ladrón, A and Álvarez-Cienfuegos, L. (2012). Clinical psychology. CEDE Preparation Manual PIR, 02. CEDE. Madrid.