Dementia with Lewy bodies: symptoms, causes and relationship with Alzheimer's
The term "dementia" refers to a set of diseases that cause a progressive deterioration of functioning as a result of brain degeneration. Although not as well known as dementia due to Alzheimer's disease, the one that occurs as a result of the accumulation of Lewy bodies is also very prevalent.
In this article we will describe What is dementia with Lewy bodies and what are their symptoms and causes main. We will also analyze the physiopathological characteristics of this disease in comparison with those of Alzheimer's and Parkinson's, which share remarkable characteristics, and we will briefly review its history.
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What is dementia with Lewy bodies?
Dementia with Lewy bodies is a neurodegenerative disease that is part of the group of cortical dementias, such as Alzheimer's disease and Pick's. In this set of disorders, the brain deterioration characteristic of dementias affects the cortex, which causes a very significant alteration in the higher cognitive functions.
Consequently, people with some type of cortical dementia usually have symptoms such as memory problems, disorientation, emotional instability, impulsivity and deterioration of complex cognitive processes such as abstraction and social judgment. These functions depend mostly on the activity of the frontal lobes of the brain.
Dementia with Lewy bodies is associated with presence in the brain of anomalous cellular structures relatively specific to this disease, and that give it a name. The degeneration of the cerebral cortex causes multiple symptoms and signs, the most characteristic being parkinsonism, visual hallucinations and fluctuations in attention.
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History, diagnosis and prevalence
This disease was first described by Kenji Kosaka in 1976; however, deposits known as Lewy bodies had been discovered by Frederic Lewy in the early years of the twentieth century. In the decade of 1990 the advances in diagnostic techniques allowed to detect the disease observing the brain after the death.
At present, it is known that it is the third most common type of dementia, surpassed only by that due to Alzheimer's disease and mixed dementia, in which the anterior and vascular dementia are combined. Research on epidemiology indicates that between 10 and 15% of dementias are due to Lewy bodies .
This dementia occurs more frequently in men than in women, although the differences in prevalence are not very large. It is more common in people who are over 60 years old, but it tends to appear later: the average age of onset of symptoms is around 75 years.
Symptoms and main signs
Dementia with Lewy bodies is a progressive disease; As such, the deficits and alterations it causes increase as the disease progresses and spreads through the brain. In spite of being a cortical dementia, memory problems are not very evident during the early phases of the disease, although they happen to be later.
The symptoms and cardinal signs of dementia with Lewy bodies there are three: fluctuations in attention and alertness, which cause episodes of confusion; Parkinsonian type manifestations such as quakes at rest, rigidity and slowness in movements; and recurrent visual hallucinations, which can be very vivid.
Along the course of the disease, other dysfunctions also appear in executive processes, such as those that affect visuospatial cognition and temporal and spatial orientation, as well as delusions, difficulties in walking, frequent falls, symptoms of depression and alterations. of REM or REM ("rapid eye movement") sleep.
Causes and physiopathology
Although it is not known exactly what is the cause of dementia with Lewy bodies, it is known to be associated with the PARK11 gene and that also shares a genetic basis with Alzheimer's disease , related to failures in the synthesis of apolipoprotein E. However, most cases of this disease is not due to hereditary factors.
At the pathophysiological level, the most characteristic feature of this dementia is the presence of Lewy bodies, accumulations of alpha-synuclein protein in the cytoplasm of neurons. This alteration is due to errors in phosphorylation, a process related to the activity of proteins and metabolism.
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Relationship with Alzheimer's and Parkinson's dementias
Lewy bodies not only appear in the dementia that concerns us, but are also present in Parkinson's disease, in multiple systemic atrophy and in Alzheimer's disease; in the latter case, they are found concretely in the CA2-3 region of the hippocampus, a fundamental structure in the consolidation of memory.
In addition to Lewy bodies we can find amyloid plaques , one of the typical signs of Alzheimer's dementia, and deficits in the neurotransmitters dopamine and acetylcholine, as occurs in Parkinson's disease. This is why Lewy disease is often referred to as a midpoint between the other two, etiologically and symptomatically.
Unlike what happens in Alzheimer's disease, in dementia with Lewy bodies no atrophy is observed in the cortex of the middle part of the temporal lobes during the early stages of the disease. This fact explains part of the symptomatic differences between both dementias, particularly the course of memory problems.
