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Cortical dementias: Alzheimer's, Pick, Lewy bodies and lobar atrophies

Cortical dementias: Alzheimer's, Pick, Lewy bodies and lobar atrophies

Types of dementia

Content

  • 1 What is dementia
  • 2 Alzheimer's disease
  • 3 Lewy body disease
  • 4 Lobar atrophies

What is dementia?

The word "dementia" describes a set of symptoms that may include memory loss and thinking difficulties, problems with problem solving or language. These changes are usually small, but for someone with dementia it means they have become severe enough to affect daily life. A person with dementia may also experience changes in their mood or behavior.

50% of dementias are due to Alzheimer's disease. This, like other cortical dementias, affects the functions supported by the Cortex, like memory (amnesia), the language (aphasia), and perceptual and manipulative skills (agnosia Y apraxia).

In general, primary dementias, such as Alzheimer's, are usually irreversible. There are some diseases, however, that present with treatable and reversible dementias. This is the case of dementias associated with metabolic and deficiency diseases (hepatic encephalopathy or vitamin B-12 deficiency, for example), poisoning due to drugs or metals, or in infectious pathologies, such as encephalitis or meningitis.

Alzheimer disease

Disease Alzheimer's is the most common form of dementia, which affects up to 70% of all people with dementia.

This disease was first described in 1907 by Dr. Alois Alzheimer with the case of Auguste Deter, a middle-aged woman with dementia and specific changes in her brain. During the next 60 years, Alzheimer's disease was considered a rare condition that affected people under 65. It was not until the 1970s that Dr. Robert Katzman declared that "senile dementia" and Alzheimer's disease were the same disorder and that it was not a normal part of aging.

Alzheimer's disease is associated with age and affects approximately 10% of the population over sixty-five increasing its prevalence up to 50% in people over eighty-five years. Life expectancy once diagnosed is between five and ten years.

Neuropathological characteristics

Dr. Alzheimer examined the brain of his patient Mrs. Deter after his death and observed a significant reduction of the outer layer of the cerebral cortex, region involved in memory, language and judgment. He also found two types of deposits in the brain of Deter, some were plates known by the name of senile plates and the other type of deposit were brain cells known as neurofibrillar clews. These plaques deteriorate the synapses, so signals cannot pass between brain cells. The clews kill brain cells preventing normal transport of food and energy around the brain cell.

Distribution of senile plaques and neurofibrillar clews in advanced stages of Alzheimer's disease.

The external part of the brain is usually the affected area First because of the disease. The short term memory loss It is, therefore, one of the first symptoms of Alzheimer's disease. But as the disease progresses to deeper parts of the brain, long-term memory is also lost. The disease also affects many of the other functions of the brain and, consequently, many other aspects of behavior are affected.

These pathological changes are first observed in the hippocampus and the parietal association cortex, and spread progressively throughout the cortex and the rest of the brain.

Subsequently there is also a significant loss of cholinergic neurons in the basal forebrain, especially in the Meynert basal nucleus.

At the same time, there is a decrease in the levels of norepinephrine, serotonin and somatostatin (a neuropeptide) in the frontal lobe, occipital and hippocampus.

Causes of Alzheimer's disease

The causes of the disease are being investigated, which surely include factors in the environment, biochemical alterations and immune processes. It is something that can vary from person to person and may be due to one factor or several factors. However, some genes that could be involved in the same family have been located. For example, a gene on chromosome 21 which codes for an aberrant precursor of the b-family protein of senile plaques. Likewise, genes involved in other familiar forms of the disease have also been located in the chromosomes 14 and 1. A genetic marker that increases the risk of Alzheimer's disease is the presence of allele 4 in the alipoprotein E gene, located on chromosome 19. This protein is related to lipid metabolism, and has an affinity for the b-family protein of senile plaques. The presence of an allele 4 triples the chances of suffering from Alzheimer's disease, and the presence of two alleles 4 ensures that Alzheimer's disease will be suffered from the age of eighty.

Alzheimer's disease symptoms

In the early stages, the symptoms of Alzheimer's disease can be very subtle. However, it often starts with lapses in memory and difficulty finding words suitable for everyday objects.

Other symptoms may include:

  • Persistent and frequent memory difficulties, especially of recent events
  • A less precise type of convergence
  • Apparent loss of enthusiasm for previously enjoyed activities
  • Take more time to do routine tasks
  • Forget known people or places
  • Inability to process questions and instructions
  • Deterioration of social skills
  • Emotional unpredictability

Symptoms vary and the disease progresses at a different rate depending on the individual and the areas of the brain affected. A person's abilities can fluctuate day by day, or even within the same day, getting worse in times of stress, fatigue or poor health.

Treatment

Unfortunately, there is currently no effective treatment for Alzheimer's disease. Often patients are treated symptomatically, with neuroleptics, antidepressants, anxiolytics… Drugs that increase cholinergic neurotransmission are also used, since it is assumed that memory loss is due in part to the involvement of this neurotransmission system. Acetylcholinesterase inhibitors are often used, the enzyme that degrades the acetylcholine in the synaptic space.

Other important features of Alzheimer's disease are the anosognosia, or ignorance of the cognitive deficit by the sufferer, changes in character, with an increase in irritability and / or apathy and lack of initiative, affective disorders, such as anxiety and depression, and sometimes psychotic symptoms, such as delusions and / or hallucinations.

Lewy body disease

Dementia with Lewy bodies is a progressive brain disorder in which Lewy bodies (abnormal deposits of a protein called alpha-synuclein) they accumulate in areas of the brain that regulate behavior, cognition and movement.

It is a complex disease that can present with a variety of symptoms that include problems with thinking, memory, movement, sleep and / or changes in behavior, among other physical, cognitive and behavioral symptoms.

It also affects autonomic bodily functions, such as blood pressure control, temperature regulation and bladder and bowel function. Progressively debilitating, this disease can cause people to experience visual hallucinations or act your dreams.

It is characterized by the appearance of Lewy bodies and occasionally also senile plates. Lewy bodies are located in the cortex, and are also observed in subcortical structures, such as the black substance.

Lewy body disease has symptoms that may closely resemble other diseases such as Alzheimer's and Parkinson's, so it is sometimes difficult to diagnose.

Pick's disease

Pick's disease is a type of dementia similar to Alzheimer's, but much less common. It is also a type of disorder known as frontotemporal dementia or frontotemporal lobar degeneration.

Pick's disease is a rare type of age-related dementia that affects the frontal lobes of the brain. It affects the parts of the brain that control emotions, behavior, personality and languageIt causes speech problems such as aphasia, behavioral difficulties and, ultimately, death. It was first described by Czech neurologist and psychiatrist Arnold Pick in 1892. In some previous medical texts, Pick's disease is used interchangeably with "frontotemporal dementia.

Our brain uses a transport system to help carry the nutrients it needs from one place to another. This system is made of proteins that guide nutrients where they should go. With Pick's disease, proteins do not work as they should.

Sometimes it can be confused with atypical forms of Alzheimer's disease, but it has differential characteristics:

  • The affectation is limited to the frontal cortices (including the caudate nucleus) Y temporary (including the hippocampus and the amygdala).
  • Histologically it is characterized by presence of spherical cells, called Pick bodies.
  • The first symptoms usually appear between the ages of forty and fifty. It is less frequent than Alzheimer's disease.

It is characterized by mood and affective disorders, and behavioral changes, and pseudopsychopathy and / or pseudodepression may occur. Disinhibition is observed, with hyperorality (change of eating habits and introduction of inedible objects in the mouth) and hypersexuality (with absence of discrimination based on age, sex or degree of relationship with the person). May also appear exhibitionist behavior and important obsessive-compulsive traits. The patient is anosognosic. Memory, language and executive functions are often altered.

Those affected by Pick's dementia may presentsocially inappropriate behaviors, such as urinating in public or explicit sexual comments. There may be an increase in sexual activity and strange behaviors, such as masturbation in public. Their eating habits are altered, they gain weight very quickly or they try to eat inedible things (plaster, feces or spoiled food). They tend to disregard economic issues and gradually isolate themselves from their social environment, also losing linguistic abilities ending in mutism.

Lobar atrophies

There are brain degenerations that affect only one or two brain lobes, and that, therefore, have an exclusive symptomatology of the functions carried out by the affected brain lobes.

One of them is slowly progressive aphasia, which results from a degeneration of the perisylvian region of the left hemisphere. The lesion focused on the right parietal lobe it is known by the name of apraxia slowly progressive, and mostly affects constructive practices and spatial perception. Finally, the posterior cortical atrophy, which affects parietooccipital cortices. Although histologically it seems that they differ from Alzheimer's or Pick's dementias, it is not clear if they are only the first phase of a generalized cortical dementia.

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