Scientific advances in the field of medicine have made it possible throughout history that we have been able, little by little, to overcome and survive a large number of diseases of different types, improving the quality of life and increasing our life expectancy. life.
However, there are still diseases, many diseases and disorders that continue to pose a serious problem to our health and survival. Some of the main diseases to be eliminated today are cancer, AIDS, or the type of disorders this article is dedicated to: the different types of dementias.
The concept of dementia
With the gradual increase in life expectancy and the decline in the birth rate in our society, the average age of the population is gradually increasing. So little by little, he sees an increasing increase in the aging of the population, thus being more and more frequent among age-related or aggravated disorders. Among them are dementias.
Dementia is understood to be the type of neurodegenerative disorder of organic origin that is characterized by a loss of one or more mental faculties, which usually includes memory as well as other capacities which interfere with the good vital functioning of the person and cause discomfort and / or loss of autonomy. The deficiencies detected represent an aggravation compared to the previous action and do not occur only in a situation of altered consciousness.
This is a type of chronic, progressive and irreversible disorder (Although in some cases the degenerative process may stop and there may even be complete or partial recovery, such as those caused by hydrocephalus, poisoning or infection), caused by alterations in the body related to illness, substance use or deterioration and / or degeneration of normal brain processes. In addition, their effects may vary depending on the types of memory that affect them the most.
Classes according to the location of the lesions
In dementias, the nervous system gradually deteriorates, destroying different structures and nerve bundles and over time losing different functions 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 behind the degeneration.
Depending 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 in the cerebral cortex. Due to the involvement of this part of the brain in information processing and in-depth information processing work, this deficiency results in the gradual 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 usually first an affectation of both antegrade and retrograde memory (In the latter case, temporarily graduated) followed by the so-called aphasic-apraxo-agnostic syndrome, in which problems with speech, sequencing of movements and recognition of stimuli appear.
Some of the most well-known cortical dementias are Alzheimer’s disease in its early stages, frontotemporal dementia, Pick’s disease, or Lewy body dementia.
2. Sub-cortical dementias
Subcortical dementias are those in which the involvement occurs particularly in subcortical structures, such as the basal ganglia, thalamus or brainstem. Some of the most recognizable symptoms are those related to a high level of motor slowdown, presence of passivity, lack of motivation, withdrawal, apathy, emotional flattening and changes in the frontal lobes leading to loss of executive functions.
While there is usually memory loss as well, in subcortical dementias it is just as serious regardless of when you are asked to remember it, usually with poor retrograde memory. Among the best known are dementia caused by Parkinson’s disease, HIV and Huntington’s disease.
3. Axial dementias
This type of dementia mainly affects the limbic system, its main symptoms being impaired learning ability and working memory. Although it is not generally considered to be dementia, Korsakoff syndrome is the best known case.
4. Global dementias
These are dementias in which features associated with lesions appear in both cortical and subcortical areas. Although the lesions may originate in parts of the brain, in most dementias the degeneration of nerve structures it ultimately affects the whole brain over time, Such as Alzheimer’s disease.
Main types of dementia
Regardless of its neuroanatomical location, some of the main types of dementia are as follows.
1. Alzheimer’s disease
The best known and most common dementia, Alzheimer’s disease, is dementia of cortical origin (Although it ends up being cortico-subcortical) of insidious origin and slow progression which begins in the parietotemporal area of the brain, with a gradual advance towards the front 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 large amount of neurofibrillary tangles and beta-amyloid plaques.
There are usually three distinct phases. The first symptoms are usually recent memory impairment, accompanied by anterograde amnesia. A slight anomie and an impoverished language appear. Other disorders also appear as a loss of olfactory capacity, loss of interest and motivation, rigid behavior and irritability. At this point, there is often emotional pain and even depression, as there is usually awareness of the disease. Yet 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-agnósico syndrome usually appears. Cognitive abilities deteriorate dramatically, with retrograde amnesia and a high level of disorientation occurring. In this state, the individual he is no longer able to lead an independent life, requiring constant supervision.
In the last phase, the subject is already able to recognize neither significant people nor himself, losing speech to the point of silence and basic skills of everyday life. With time it is also to lose motor capacities, until arriving at the permanent encamamiento.
Frontotemporal dementias are a subgroup of dementias also called taupaties (because there are alterations in the tau protein) which are characterized because the main damage occurs in the frontal and temporal lobes, resulting in major personality and language disorders.
There are three variants, of the frontal characterized by changes in personality and behavior, semantic dementia in which the loss of meaning of words is highlighted without changing other aspects of language and progressive primary aphasia in which difficulties appear. in all areas of language.
3. Lewy body dementia
The most visible symptoms of this cortical dementia are problems with attention and severe executive functions, presenting with aphaso-apraxo-agnostic syndrome, Parkinson-like motor symptoms, and hallucinations and delusions. Gradual start and fast course, it is very common for there to be intense psychotic symptoms and disorientation, As well as loss of consciousness sudden.
Structures known as Lewy bodies typically appear in most of the cerebral cortex, with dopamine deficiency.
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 black streaky pathway) gradually degenerate. In these areas, a high prevalence of Lewy bodies can be observed.
This degeneration is caused by a deficiency in the functioning of dopamine, being the most characteristic symptoms the appearance of parkinsonian tremors which mostly occur in a state of overhaul. There are also difficulties in walking, slowing down, bending over, not moving and expressing the face.
The dementia associated with this disease, which is subcortical in type, does not appear in all cases, although as the number of years increases since the onset of symptoms, it is more likely to appear. Typical symptoms of this dementia are slow down physically and mentally, with high passivity.
6. For Huntington’s Korea
Huntington’s disease is an autosomal dominant genetic disorder of complete penetration affecting in particular virulently the neurons governed by the neurotransmitter GABA and acetylcholine in the basal ganglia.
Slow and progressive onset, in this neurodegenerative disease, constant uncontrolled movements appear, in the form of twists and twists of the body parts recalling or a dance.
The process of dementia, of the subcortical type, usually begins with behavioral and personality changes with marked impairment of memoryAlso appearing over time an affectation in the frontal lobe which leads to a progressive loss of executive functions such as planning and sequencing.
7. Dementia due to HIV
Infection with HIV, after several years of development, can in some cases eventually cause the degeneration of multiple structures and pathways in the brain, causing a specific type of dementia known as the HIV-associated dementia complex.
This type of dementia classified as subcortical is characterized by the presence of slowdowns, reading problems, loss of spontaneity and hallucinations, decreased tracking movements and movement disorders in general. It usually progresses quickly to severe dementia which leads to the death of the patient.
8. Vascular or multi-infarction dementia
This type of dementia is caused by the presence of strokes, in the form of bleeding or stroke, which affect one or more parts of the brain. The effects can vary widely depending on the affected area, resulting in impaired functions such as memory or language.
It is a type of dementia which, unlike most, it starts suddenly and abruptly, usually noticing the change in the patient’s condition and physical or mental abilities. It is common for deterioration to occur in a phased manner, also with periods of partial recovery.
American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders. Fifth edition. DSM-V. Masson, Barcelona.
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