Differences between dementia and Alzheimer's

There is 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 impairment, it is advisable to specifically clarify which ones are 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 of the three are still prevalent: vascular dementia, Lewy body dementia and dementias frontotemporal. 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 common neurological disorders"

Alzheimer's disease: main features

The DSM-IV defines dementia as a set of cognitive deficits including significant memory impairment, 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 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 glial cell hyperproliferation.

From a symptomatic point of view, the main peculiarity of Alzheimer's disease with Regarding other causes of dementia, it begins by affecting the temporal and parietal lobes of the brain. This explains the early signs of Alzheimer's: recent memory and learning problems, personality changes, and depressive symptoms.

Cognitive decline continues to progress irreversibly. Between 3 and 5 years after the onset of the disease judgment is impaired, disorientation is noticeably worse (especially space, which causes affected people to get lost in the street) and psychotic symptoms such as hallucinations and delusions may appear.

The final phase of Alzheimer's disease is characterized, among other signs, by autopsychic disorientation, lack of recognition of relatives, the complete loss of language and increasing difficulties in walking until reaching apraxia of the March. 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

Below 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 or multi-infarct dementia when brain -and therefore cognitive- deterioration occurs 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 the heart attacks, as well as their intensity. It is common for the onset to be abrupt, coinciding with a cerebrovascular accident, and then the deterioration progresses in a staggered manner, unlike the linearity typical of Alzheimer's.

However, vascular dementia very often occurs concurrently 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 mnestic symptoms central.

• You may be interested: "Types of dementias: forms of loss of cognition"

2. Lewy body dementia

This type of dementia is characterized by the presence of Lewy bodies, structures derived from the degeneration of proteins of the cell cytoplasm, in the frontal, parietal and temporal cortex of the brain, as well as in the substance black. Neuritic plaques of beta-amyloid protein are also found, as in Alzheimer's.

The most characteristic signs of this type of dementia are visual hallucinations, attentional deficits (which cause sudden fits of confusion), alterations in executive functions and parkinsonian symptoms such as rigidity and tremors at rest. Memory impairment is less severe than in Alzheimer's.

Another relevant 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 feature largely explains the similarity of this disorder to Parkinson's disease.

3. Frontotemporal dementias

That 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 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 memory impairment is less obvious than in those due to Alzheimer's disease, especially during 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 of Alzheimer's. However, her neuritic plaques are absent. Both pathophysiological features also characterize dementia due to Creutzfeldt-Jakob disease.