There is quite a widespread confusion between the term “dementia” and Alzheimer’s disease. Although this is the most common disorder in this group of disorders associated with pathological cognitive impairment, it should be specified specifically which sounds differences between Alzheimer’s disease and the other types of dementia that exist.
In this article, we will analyze what distinguishes the most common cause of dementia from the three that follow it in prevalence: vascular dementia, dementia with Lewy bodies and frontotemporal dementia. A fourth very common type is mixed dementia, which combines the signs of Alzheimer’s disease with those of vascular dementia.
Alzheimer’s disease: main features
DSM-IV defines dementia as a set of cognitive deficits that include significant impairment of memory, In addition to aphasia, apraxia, agnosia and / or alterations in executive functions, such as planning and sequencing. Although many of the diseases that cause dementia are progressive in nature, this is not always the case.
Dementia due to Alzheimer’s disease is the most common of all. At the pathophysiological level, it is characterized by the presence of neurofibrillary buds (conglomerates of tau proteins) and neuritic plaques or senile deposits of beta-amyloid peptide, the presence of which is associated with neuronal degeneration and hyperproliferation of glial cells.
From a symptomatic point of view, the main peculiarity of Alzheimer’s disease compared to other causes of dementia is that it begins to affect the temporal and parietal lobes of the brain. This explains the early signs of Alzheimer’s disease: recent learning and memory problems, personality changes and depressive symptoms.
Cognitive impairment continues to progress irreversibly. Between 3 and 5 years after the onset of the disease the ability to judge is impaired, disorientation is markedly worsened (Especially the spatial, which causes those affected to get lost in the street) and psychotic symptoms such as hallucinations and delusions may appear.
The final stage of Alzheimer’s disease is characterized, among other signs, by autopsychic disorientation, lack of recognition of neighboring circles, complete loss of language and increasing difficulty in walking until gait apraxia. As in many other dementias, in the final phase, the affectation is global and causes death.
Differences between Alzheimer’s disease and other dementias
Below we describe the main features that distinguish Alzheimer’s disease from the following three most common causes of dementia.
1. Vascular dementia
We speak of vascular dementia or multi-infarction when brain disorders – and therefore cognitive disorders occur as consequence of repeated blows. It is usually diagnosed in the presence of arteriosclerosis, which is defined as a hardening of the arteries that obstructs blood flow.
In these cases, the symptoms and signs vary depending on the areas of the brain affected by the heart attacks, as well as their intensity. It is common for the onset to be abrupt, coinciding with a stroke, and the deterioration to progress gradually in stages, unlike the linearity of Alzheimer’s disease.
However, vascular dementia very often occurs at the same time as Alzheimer’s disease. When that happens we talk about mixed dementia or Alzheimer’s disease with vascular component. In these cases, the signs also vary, but the temporoparietal involvement makes the mnemonic symptoms central.
2. Lewy body dementia
This type of dementia is characterized by the presence of Lewy bodies, structures derived from the degeneration of proteins in the cellular cytoplasm, in the frontal, parietal and temporal cortex of the brain, as well as in the substantia nigra. Neuretic plaques of beta-amyloid protein are also found, such as in Alzheimer’s disease.
The most characteristic signs of this type of dementia are visual hallucinations, Attention deficits (which cause sudden episodes of confusion), changes in executive function and symptoms of Parkinson’s disease such as stiffness and tremors while at rest. Memory problems are less serious than with Alzheimer’s disease.
Another important difference between Lewy disease and Alzheimer’s disease is the fact that in the former there is a deficit in the levels of the neurotransmitter dopamine. This characteristic largely explains the similarity of this disorder to Parkinson’s disease.
3. Frontotemporal dementias
this term includes primary progressive aphasia and semantic dementia. Frontotemporal dementias begin with involvement of the frontal and / or temporal lobes; sometimes the frontal lobe is damaged early on in Alzheimer’s disease (and in particular the limbic region, associated with emotions), but this is not always the case.
In these dementias, the impairment of memory is less evident than in those due to Alzheimer’s disease, especially in the early stages. In contrast, language problems and behavioral disinhibition are more pronounced in this group of disorders.
Frontotemporal dementias are associated with mutations in the gene from which the tau protein is synthesized, Which causes neurofibrillary tangles similar to those in Alzheimer’s disease. However, neuritic plaques are absent. The two pathophysiological traits also characterize dementia due to Creutzfeldt-Jakob disease.