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Parkinson's disease (PD) is characterized as a complex neurological disorder, with classic motor symptoms that are mainly associated with the development of Lewy bodies within nerve cells and with the loss of dopaminergic neurons in the substantia nigra. Among the most characteristic motor symptoms of the disease, tremor, rigidity, bradykinesia, postural instability and gait difficulty are included. Consequently, such motor comorbidities directly impact the patient's life, affecting quality of life, increasing the risk of falls, and decreasing independence in general. PD is currently the second most prevalent neurodegenerative disease (after Alzheimer's disease), with a rate of 14 affected per 100,000 inhabitants; when considering the population over 65 years old, the values rise to 160 affected per 100,000 inhabitants. Approximately 60,000 new cases of PD are diagnosed each year in the United States, in addition to the more than one million cases already diagnosed. In Brazil, it is estimated that 200,000 individuals have PD in the general population, with a high prevalence in people aged between 60 and 79 years. About 36,000 new cases arise in the country each year. The incidence rate of Men-Women varies between 1.3 and 2.0 in most of the recorded data. In 2012, Noyce et al. analyzed 30 environmental factors that could be related to the development of PD, among which those that were highly significant: exposure to pesticides, previous injury to the skull region, living in a rural area, use of beta-blockers. , workers in rural areas and consumption of water from wells. Among the protective factors found are: smoking, use of non-steroidal anti-inflammatory drugs, caffeine consumption, use of calcium channel blockers and alcohol consumption. Among the genetic factors best described in the literature are the SNCA genes, which encode the alpha-synuclein protein; mutations in LRRK2; mutations in the GBA gene, which encodes the beta-Glucocerebrosidase enzyme, which is the main genetic risk factor found until then for the development of PD.

Lewy bodies were first described in 1912 by Friedrich Henrich Lewy, becoming a major pathological marker of PD. They are found inside neurons and are made up of neurofilaments with aggregates of alpha-synuclein and ubiquitin. In 2007, through the study by Wakabayashi, he showed that Lewy bodies were not directly related to the causes of PD, but to its symptoms.

In general, the pathophysiology of PD is characterized by a progressive neuronal loss of the compact part of the substantia nigra of the midbrain, requiring a loss of more than 60% for the main symptoms of the disease to appear. However, in addition to the deficit in the dopaminergic pathway, other neurotransmitters may also be involved in the pathophysiology of PD. In the noradrenergic system, the locus coeruleus, presents the loss of 50 to 80% of pigmented neurons, in addition to the reduction of neurons in the dorsal vagus nucleus and in the supraoptic and paraventricular hypothalamic nuclei, accompanied by a decrease in the function of the noradrenergic projections; In the serotonergic system, a reduction of 57.8% of neurons in the dorsal raphe nucleus is observed; And in the cholinergic system, a reduction of 50 to 60% of cholinergic neurons in the dorsal raphe nucleus was observed.

In 2003, a study developed by Braak et al. showed that PD begins in Meissner's gastric autonomic plexus and in the olfactory neural endings, propagating to the brainstem (midbrain), precisely in the dorsal vagus nuclei, glossopharyngeal nucleus, olfactory and in the intermediate area. From there, evolution is divided into 5 more stages, namely: 1 - raphe nuclei, gigantocellular nucleus and locus coeruleus; 2 - compact part of the substantia nigra; 3 - forebrain areas of the temporal mesocortex; 4 - areas of association of the frontal neocortex; 5 - neocortex association areas, premotor and motor areas.

The main motor symptoms of PD are bradykinesia, hypokinesia, akinesia, tremor and rigidity, as well as balance and gait deficits. In addition, cognitive disorders, memory deficits, problems related to visuospatial dysfunction, difficulties in performing sequential and repetitive movements, freezing and slow psychological responses are often present. Decreased writing and problems in the voice and swallowing of individuals can also be observed. Among the main clinical symptoms of PD is tremor, which in about 50% of cases begins in the distal extremities. In rest situations, the decrease or disappearance of this symptom is noticeable, which returns if the individual maintains a more prolonged action or posture. Bradykinesia (slowness of movement) is due to an imbalance between the inhibitory and excitatory systems, resulting from the absence of dopamine in the striatum, affecting mainly automatic movements, generating a general poverty of movement and frequent complaint of weakness. Patients with PD have a high chance of acquiring a posture with their center of gravity forward, generating a bent or flexed posture. There is also a decrease in postural reflexes, such as protective extension, balance, and righting reactions. The gait presents itself as a slow, shuffling gait with a shortened stride length.