Lewy body dementia: symptoms and causes

The term "dementia" refers to a group of diseases that cause a progressive deterioration of functioning as a consequence of the degeneration of the brain. Although it is not as well known as dementia due to Alzheimer's disease, that which occurs as a result of the accumulation of Lewy bodies is also very prevalent.

In this article we will describe what is Lewy body dementia and what are its symptoms and causes main. We will also analyze the pathophysiological characteristics of this disease in comparison with those of Alzheimer's and Parkinson's, which share remarkable characteristics, and we will briefly review their history.

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What is Lewy body dementia?

Lewy body dementia is a neurodegenerative disease that falls within the group of cortical dementias, such as Alzheimer's disease and Pick's disease. In this group of disorders, the cerebral deterioration typical of dementias mainly affects the cortex, which causes a very significant alteration in higher cognitive functions.

Consequently, people with some type of cortical dementia usually have symptoms such as memory problems, disorientation, emotional instability, impulsivity and impairment 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 cell 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 being parkinsonism, visual hallucinations, and fluctuations in attention.

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History, diagnosis and prevalence

This disease was described for the first time by Kenji Kosaka in 1976; however, the deposits known as Lewy bodies had been discovered by Frederic 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 due to Alzheimer's disease and mixed dementia, in which the above and the vascular. Research on epidemiology indicates that 10-15% 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 great. 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

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

The Cardinal Signs and Symptoms of Lewy Body Dementia there are three: fluctuations in attention and alertness, which cause episodes of confusion; Parkinsonian-type manifestations such as tremors at rest, rigidity and slowness in movements; and recurrent 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 to temporal and spatial orientation, as well as delusions, difficulties in walking, frequent falls, symptoms of depression and alterations of the REM or REM sleep ("Of rapid eye movements").

Causes and pathophysiology

Although the exact cause of Lewy body dementia is not known, it is known to be associated with the PARK11 gene and to also shares a genetic basis with Alzheimer's disease, related to failures in the synthesis of apolipoprotein E. However, most cases of this disease are 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 protein activity and metabolism.

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Relationship with Alzheimer's and Parkinson's dementias

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

Besides Lewy bodies we can find amyloid plaques, one of the typical signs of Alzheimer's dementia, and deficits in neurotransmitters dopamine and acetylcholine, as in Parkinson's disease. This is why Lewy disease is often spoken of as a middle ground between the other two, etiologically and symptomatically.

Unlike Alzheimer's disease, Lewy body dementia is not observed atrophy 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.