Differences between Parkinson’s disease and Alzheimer’s disease

A summary of the differences between these two neurodegenerative diseases.

Parkinson's disease and Alzheimer's disease, respectively, are the causes of two common types of neurological disorders related to dementias.

However, there are many aspects that make it possible to distinguish between one disease and the other; in this article, we will learn about the most important differences between Parkinson's disease and Alzheimer's disease..

Differences between disease and dementia

We must be aware of the differences between disease and dementia, since the disease does not always lead to dementia (cognitive impairment), although it usually does.

Thus, the term dementia refers to a set of symptoms that appear as a result of neurological damage or disease.

Parkinson's disease, on the other hand, does not always lead to dementia (it does in 20-60% of cases). (it does in 20-60% of cases); on the other hand, Alzheimer's disease usually does lead to dementia (and early).

Differences between Parkinson's disease and Alzheimer's disease

Regarding the differential diagnosis between Parkinson's and Alzheimer's diseases, there are several differences in their presentation. We will see them in different blocks:

1. Dementia

In Alzheimer's disease, dementia appears early, and attention and memory are particularly affected. On the other hand, in Parkinson's disease, dementia appears early, and attention and memory are particularly affected, in Parkinson's disease, if dementia appears, it appears later..

On the other hand, Alzheimer's dementia is cortical (involvement of the cerebral cortex), and Parkinson's dementia is subcortical (involvement of subcortical areas).

Broadly speaking, cortical dementias involve cognitive disturbances, and subcortical dementias involve motor disturbances.

2. Other symptoms

In Alzheimer's disease delirium appears occasionally, and in Parkinson's disease this occurs less frequently.

In both Alzheimer's disease and Parkinson's disease, visual hallucinations may appear occasionally. On the other hand, in Alzheimer's disease, delirium appears typicallyand in Parkinson's disease they appear only occasionally.

Motor symptoms 3.

Parkinsonism (clinical syndrome characterized by tremor, bradykinesia, rigidity, and postural instability) is the first manifestation of Parkinson's disease; in contrast, this symptom is rare in Alzheimer's disease.

Similarly, rigidity and bradykinesia appear typically in Parkinson's disease, and occasionally in Alzheimer's disease.and occasionally in Alzheimer's disease.

Tremor is typical in Parkinson's disease and rare in Alzheimer's disease.

4. Cognitive symptoms

In Parkinson's there are failures in retrieval, and in Alzheimer's there are failures in coding (memory).

5. Pathological signs

Senile plaques in the brain appear typically in Alzheimer's disease, but rarely in Parkinson's disease. Similarly, neurofibrillary tangles also appear typically in Alzheimer's disease, but rarely in Parkinson's disease.

Cortical Lewy bodies appear rarely in Alzheimer's and more often in Parkinson's (occasionally). Subcortical Lewy bodies, on the other hand, are typical in Parkinson's and rare in Alzheimer's disease.

On the other hand, acetylcholine deficiency is typical in Alzheimer's disease and occasional in Parkinson's disease. Finally, dopamine depletion appears only in Parkinson's disease.

6. Age of onset and prevalence

Finally, continuing with the differences between Parkinson's disease and Alzheimer's disease, we know that Parkinson's disease appears earlier than Alzheimer's disease (at 50-60 years of age), while Alzheimer's disease usually appears a little later, after 65 years of age.

On the other hand, as far as dementias are concerned, the prevalence of dementia due to Alzheimer's is higher (it is the leading cause of dementia), and this is 5.5% in Spain and 6.4% in Europe.

Symptoms in Alzheimer's disease and Parkinson's disease

Now that we have seen the differences between Parkinson's disease and Alzheimer's disease, let's learn more about the symptoms of each of these diseases:

1. Alzheimer's disease

Alzheimer's disease is is a neurodegenerative disease that manifests itself as cognitive impairment (dementia), behavioral (dementia), behavioral disorders and emotional disorders. When it develops into dementia and according to the DSM-5, it is called Major or Mild Neurocognitive Disorder due to Alzheimer's disease.

The symptoms of Alzheimer's disease change as the disease progresses. We can differentiate three types of symptoms according to the three phases of Alzheimer's disease:

1.1. First phase

The first deterioration appears and lasts between 2 and 4 years. Anterograde amnesia (inability to create new memories). (inability to create new memories), changes in mood and personality, as well as impoverished language (anomias, circumlocutions and paraphasias).

1.2. Second phase

In this phase the deterioration continues (lasting 3 to 5 years). Aphaso-apraxo-agnostic syndrome, retrograde amnesia and impaired judgment, as well as alterations in abstract thinking appear. Instrumental activities of daily living (IADL) such as shopping or calling the plumber are already affected.

The patient is already incapable of living without supervision, and presents spatio-temporal disorientation.

1.3. Third phase

In this last phase the deterioration is already very intense, and the duration is variable. It is the advanced stage of the disease. Here, self-psychic and other people's disorientation appears, as well as mutism and inability to perform basic activities of daily living (ADL) such as eating or toileting.

Gait disturbances also appear (the "small step gait"). On the other hand, Kluver Bucy syndrome may occur.This is a syndrome in which there is a lack of fear before stimuli that should generate it, absence of risk assessment, meekness and obedience together with indiscriminate hypersexuality and hyperphagia, among others.

Finally, in this phase the patient ends up bedridden, characteristically with the adoption of a fetal posture.

2. Parkinson

Parkinson's disease is a chronic neurodegenerative disease, characterized by different motor disorders such as bradykinesia, rigidity, tremor and loss of postural control. motor disorders such as bradykinesia, rigidity, tremor and loss of postural control..

Between 20 and 60% of patients with Parkinson's disease develop Parkinson's dementia (cognitive impairment). This dementia is called Major or Mild Neurocognitive Disorder due to Parkinson's disease in the DSM-5.

Once dementia appears, the symptoms consist of: failures in memory retrieval processes, decreased motivation (apathy, asthenia and abulia), bradypsychia (slowing of the thinking process) and impoverished language. Bradykinesia (slowness of movement) also appears, although aphasia-apraxo-agnostic syndrome does not appear as in Alzheimer's dementia.

Visuospatial and visoconstructive disturbances also appear.Finally, Parkinson's is strongly related to depression.

On the other hand, it is frequent in Parkinson's dementia the presence of the disejective syndrome (alteration of the prefrontal lobe) is frequent in Parkinson's dementia.

Conclusion

As we have seen, the differences between Parkinson's disease and Alzheimer's disease are remarkable, although they share many other features. Therefore, it is important to make a good differential diagnosis of Parkinson's disease and Alzheimer's disease. it is important to make a good differential diagnosisin order to be able to carry out an appropriate treatment for each case and patient.

Bibliographic references:

• Belloch, A.; Sandín, B. And Ramos, F. (2010). Manual of Psychopathology. Volume II. Madrid: McGraw-Hill
• APA (2014). DSM-5. Diagnostic and statistical manual of mental disorders. Madrid. Panamericana.