Lewy body dementia: symptoms, causes and relationship to Alzheimer’s disease

The term “dementia” refers to a collection of diseases that cause progressive deterioration in function as a result of brain degeneration. Although it is not as well known as dementia due to Alzheimer’s disease, which occurs as a result of a build-up of Lewy bodies, it is also very common.

In this article we will describe what is Lewy body dementia and what are its 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 give a brief reminder of its history.

    What is Lewy Body Dementia?

    Lewy body dementia is a neurodegenerative disease that belongs to the group of cortical dementias, such as Alzheimer’s and Pick’s disease. In this set of disorders, the cerebral deterioration of dementia mainly affects the cortex, which causes a very significant impairment of higher cognitive functions.

    Therefore, people with a certain type of cortical dementia often have symptoms such as memory problems, disorientation, emotional instability, impulsivity and the deterioration of complex cognitive processes such as abstraction and social judgment. These functions depend mainly on the activity of the frontal lobes of the brain.

    Lewy body dementia is associated with presence in the brain of abnormal cellular structures relatively specific to this disease, and which give it its name. Degeneration of the cerebral cortex causes multiple symptoms and signs, the most characteristic of which are parkinsonism, visual hallucinations and fluctuations in attention.

      History, diagnosis and prevalence

      This disease was first described by Kenji Kosaka in 1976; however, the deposits known as Lewy Bodies had been discovered by Frédéric Lewy in the early years of the 20th century. In the 1990s, advances in diagnostic techniques made it possible to detect the disease by observing the brain after death.

      It is currently known to be the third most common type of dementia, surpassed only by Alzheimer’s disease and mixed dementia, in which old and vascular dementia are combined. Epidemiological research 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 over 60, but tends to appear later: the average age of onset of symptoms is around 75 years.

      Main symptoms and signs

      Lewy body dementia is a progressive disease; as such, the deficits and alterations it causes increase as the disease progresses and spreads in the brain. Despite being cortical dementia, memory problems are not very obvious in the early stages of the disease, although they later become so.

      The main symptoms and signs of Lewy body dementia there are three: fluctuations in attention and alertness, which cause episodes of confusion; Parkinson-like manifestations such as tremors at rest, stiffness and slowness of movement; and recurring visual hallucinations, which can be very vivid.

      Throughout 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, difficulty walking, falls frequent symptoms of depression and alterations. From REM or MOR sleep (“rapid eye movements”).

      Causes and pathophysiology

      Although it is not known exactly what causes Lewy body dementia, it is known to be associated with the PARK11 gene and that it also shares a genetic basis with Alzheimer’s disease, Linked to errors in the synthesis of apolipoprotein E. However, most cases of this disease are not due to hereditary factors.

      Physiopathologically, 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 protein activity and metabolism.

        Relationship with Alzheimer’s and Parkinson’s dementias

        Lewy bodies not only appear in dementia before us, but are also present in Parkinson’s disease, multiple systemic atrophy, and Alzheimer’s disease; in the latter case, they are found specifically in the CA2-3 region of the hippocampus, the fundamental structure of memory consolidation.

        In addition to Lewy bodies we can find amyloid plaques, One of the typical signs of Alzheimer’s dementia and dopamine and acetylcholine neurotransmitter deficiencies, as 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 Lewy body dementia 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 some of the symptomatic differences between the two dementias, especially the evolution of memory problems.

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