Differences between dementia and Alzheimer's
There is a fairly widespread confusion between the term "dementia" and Alzheimer's disease. Although it is the most common within this group of disorders associated with pathological cognitive deterioration, it is necessary to clarify in a specific way which ones differences between Alzheimer's disease and the other types of dementia that exist.
In this article, we will analyze what distinguishes the most frequent cause of dementia from the three that follow it in prevalence: vascular dementia, dementia with Lewy bodies and frontotemporal dementias. A fourth very common type is mixed dementia, which combines the signs of Alzheimer's with those of vascular dementia.
- Related article: "The 15 most frequent neurological disorders"
Alzheimer's disease: main features
The DSM-IV defines dementia as a set of Cognitive deficits that include a significant deterioration 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 have a progressive character, this is not always the case.
Dementia due to Alzheimer's disease is the most common of all. At physiopathological level, it is characterized by presence of neurofibrillary tangles (conglomerates of tau proteins) and neuritic plaques or senile, deposits of beta-amyloid peptides whose presence is associated with neuronal degeneration and hyperproliferation of glial cells.
From a symptomatic point of view, the main peculiarity of Alzheimer's disease with respect to other causes of dementia is that it starts affecting the temporal and parietal lobes of the brain. This explains the early signs of Alzheimer's: learning and recent memory problems, personality changes and depressive symptoms.
Cognitive deterioration continues to progress irreversibly. Between 3 and 5 years after the onset of the disease the judgment capacity is altered, the disorientation is noticeably worsened (especially spatial, which causes affected people to be lost in the street) and psychotic symptoms may appear as hallucinations and delusions.
The final phase of Alzheimer's disease is characterized, among other signs, by autopsychic disorientation, lack of recognition of relatives, complete loss of language and increasing difficulties to walk until apraxia of walking. As in many other dementias, In the final phase, the affectation is global and causes death .
- Related article: "Alzheimer's: causes, symptoms, treatment and prevention"
Differences between Alzheimer's and other dementias
Next we will describe the main characteristics that distinguish Alzheimer's disease from the following three most common causes of dementia.
1. Vascular dementia
We speak of vascular dementia or multi-infarct when the cerebral deterioration -and therefore cognitive- is given as consequence of repeated strokes . 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 regions of the brain that are affected by heart attacks, as well as the intensity of these. It is usual that the onset is sudden, coinciding with a stroke, and that later the deterioration progresses in a staggered manner, unlike the linearity of Alzheimer's itself.
However, vascular dementia very often occurs simultaneously with Alzheimer's disease. When this 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 mnesic symptoms central.
- You may be interested: "Types of dementia: forms of cognition loss"
2. Dementia with Lewy bodies
This type of dementia is characterized by the presence of Lewy bodies, structures derived from the degeneration of cellular cytoplasm proteins, in the frontal, parietal and temporal cortex of the brain, as well as in the substantia nigra. Neuritic beta-amyloid protein plaques are also found, as in Alzheimer's.
The hallmarks of this type of dementia are visual hallucinations , attentional deficits (which cause sudden access to confusion), alterations in executive functions and parkinsonian symptoms such as rigidity and resting tremors. The deterioration of memory is less serious than in the case of Alzheimer's.
Another relevant difference between Lewy and Alzheimer's disease is the fact that in the first there is a deficit in the levels of the neurotransmitter dopamine.This characteristic explains to a large extent the similarity of this disorder with Parkinson's disease.
3. Frontotemporal dementias
That term includes primary progressive aphasia and semantic dementia . Frontotemporal dementias begin with an involvement in the frontal and / or temporal lobes; Sometimes the frontal lobe is injured from the beginning in Alzheimer's disease (and in particular the limbic region, associated with emotions), but this is not always the case.
In these dementias the alteration of memory is less obvious than in those due to Alzheimer's disease, especially during the initial phases. On the other hand, linguistic 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 of Alzheimer's. However, neuritic plaques are absent. Both pathophysiological features also characterize dementia due to Creutzfeldt-Jakob disease.
