Differences between dementia and Alzheimer’s disease

These two types of neurological diseases associated with old age can be confused.

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 important to clarify specifically what the differences are between Alzheimer's disease and dementia. differences between Alzheimer's disease and the other types of dementia that exist.

In this article we will discuss what distinguishes the most common 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.

Alzheimer's disease: main features

The DSM-IV defines dementia as a set of cognitive deficits that include significant memory cognitive deficits that include significant impairment of memory, aphasia, apraxia, agnosia, and/orin addition to aphasia, apraxia, agnosia and/or impairments 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 tangles. presence of neurofibrillary tangles (clusters of tau proteins) and neuritic or senile plaques, peptide deposits or senile plaques, 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 respect to other causes of dementia is that it begins by affecting the temporal and parietal lobes of the brain. This explains the initial signs of Alzheimer's disease: learning and recent memory 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 worsens markedly (especially spatial disorientation, which causes (especially spatial disorientation, which causes affected persons 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 self-psychic disorientation, lack of recognition of relatives, complete loss of language and increasing difficulties in walking, leading to gait apraxia. As in many other dementias, in the final phase, the disease is global and causes death..

Differences between Alzheimer's disease and other dementias

Below we will describe the main characteristics that distinguish Alzheimer's disease from the following three most common causes of dementia.

Vascular dementia

We speak of vascular or multi-infarct dementia when brain - and therefore cognitive - deterioration occurs as a result of repeated strokes. as a result of repeated strokes.. It is generally diagnosed in the presence of arteriosclerosis, which is defined as a hardening of the arteries that obstructs blood flow.

In these cases, symptoms and signs vary depending on the regions of the brain that are affected by the infarcts, as well as the intensity of the infarcts. It is common for the onset to be abrupt, coinciding with a stroke, and then the deterioration progresses in a stepwise manner, unlike the linearity of Alzheimer's disease.

However, vascular dementia very often occurs simultaneously with Alzheimer's disease. When this happens we speak of mixed dementia or Alzheimer's disease with a vascular component.. In these cases the signs also vary, but the temporoparietal involvement makes the memory symptoms central.

2. Dementia with Lewy bodies

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

The most characteristic signs of this type of dementia are visual hallucinations, attentional deficits (causing sudden onsets of confusion), alterations in executive functions, and executive dysfunction.The most characteristic signs of this type of dementia are visual hallucinations, attentional deficits (causing sudden onsets of confusion), alterations in executive functions and Parkinsonian symptoms such as rigidity and resting tremors. Memory impairment is less severe than in Alzheimer's disease.

Another relevant difference between Lewy's 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 with Parkinson's disease.

3. Frontotemporal dementias

This term includes primary progressive aphasia and semantic dementia.. Frontotemporal dementias begin with frontal and/or temporal lobe involvement; sometimes the frontal lobe is damaged 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.This causes neurofibrillary tangles similar to those in Alzheimer's disease. However, neuritic plaques are absent. Both pathophysiological features also characterize dementia due to Creutzfeldt-Jakob disease.