Parkinson's Disease Research



Parkinson's Disease

In 1817, English physician James Parkinson described the shaking palsy, which manifested shaking hands and legs, slowness of movements, stiffness of limbs and body, as well as instability and disequilibrium. The illness has been called Parkinson's disease. Parkinson's disease affects the area of the brain called the substantia nigra, where dopamine is produced. The dopamine function implies to smooth transfer of impulses for normal movements. Parkinson's disease causes reduced production of dopamine. It interferes with the normal transmission of nerve impulses. The main symptoms of Parkinson's disease include shaking (tremor), stiffness of muscles, slowness of movement, and unstable equilibrium.

The following paper is aimed to provide a description of the disease, as well as analyze current statistics of the affected, and explanation of how Parkinson's disease affects the various body systems. However, it should be noted that there is no complete treatment of the disease.

Keywords: Parkinson's disease

Parkinson's Disease Definition

Parkinson's disease is a chronic disease, which can be usually met in older adults. It is caused by the progressive destruction and loss of neurons in the substantia nigra of the midbrain and other parts of the central nervous system, which use dopamine as a neurotransmitter. The disease is characterized by motor symptoms such as tremor, hypokinesia, muscle rigidity, and postural instability. Among other symptoms are autonomic and mental disorders, which are the results of the inhibitory influence reduction of the globus pallidus (pallidum), which are located in the anterior part of the brain, in the corpus striatum (striatum).

The damage of neuronal pallidum leads to the inhibition of the peripheral motor neurons, i.e. the spinal motoneurons (Kemp, Buxton, & Porter-Buxton, 2013). At the moment, the disease is incurable, but existing methods of conservative and surgical treatment can significantly improve the patients' quality of life. Parkinson's disease owes its name to the French neurologist Jean Charcot. He suggested naming it in honor of the British physician and author of An Essay on the Shaking Palsy by James Parkinson.

Parkinsons disease includes 70-80% of cases of Parkinson's syndrome. It is the most common neurodegenerative disorder after Alzheimer's disease. The disease occurs everywhere. Its frequency varies from 60 to 140 people per 100,000 population. However, the number of patients increases significantly among the older age groups. The proportion of people with Parkinson's disease in the age group over 60 years old is 1%, and it is 2.6% - 4% at the age of over 85 years old.

The first symptoms of the disease usually appear at the age of 55-60 years. However, in some cases, the disease can develop at the age of 40, i.e. Parkinsons disease with early-onset, or up to 20 years, i.e. the juvenile form of the disease. Men suffer from the disease more often than women. Nonetheless, it should be noted that no significant racial differences in disease patterns have been identified (Chen, Zhang, Hernan, Willett, & Ascherio, 2002).

The Etiology of Parkinson's Disease

The etiology of Parkinson's disease is not completely understood even nowadays. Etiologic risk factors include aging, genetic predisposition, as well as exposure to environmental factors (MedicineNet).

Pathologically normal aging is accompanied by the decrease in the number of neurons of the substantia nigra, as well as by the presence of Lewy bodies. Aging is also accompanied by neurochemical changes in the striatum, i.e. the reduction of dopamine and the enzyme tyrosine hydroxylase, as well as debasement in the number of dopamine receptors. The positron emission tomography proved that the rate of degeneration of the neurons of the substantia nigra during Parkinson's disease is much higher than during normal aging. About 15% of people with Parkinson's disease have a family history of the disease.

However, the genes responsible for the development of Parkinson's disease have not been identified. The reasons for the disease manifestations may also be exposed because of environmental factors, such as pesticides, herbicides, and heavy metals.

Risk factors also include accommodation in the countryside and the proximity of industrial plants and mines. However, it should be noted that the risk of Parkinson's disease development in smokers is 3 times lower than in non-smokers. It is believed that this is due to the dopamine-stimulating effects of nicotine. Moreover, this can be explained by the compounds of tobacco smoke, which act like MAO inhibitors. The usage of caffeine also protects from the development of Parkinson's disease.

Parkinsons disease affects the structure of the extrapyramidal system, i.e. the basal ganglia and substantia nigra, locus coeruleus, and others. The most pronounced changes are noted in the anterior parts of the substantia nigra. The specific symptoms of Parkinson's disease occur after the loss of 60-80% of neurons' anatomic formation.

The macroscopic changes are characterized by depigmentation of melanin-containing regions of the substantia nigra and locus coeruleus. Microscopic examination of the affected areas detected a reduction in the number of nerve cells. They define the presence of Lewy bodies. There is also the destruction of astrocytes, i.e. types of glial cells, and the activation of microglia.

Lewy bodies are formed due to the accumulation of the protein ?-synuclein in the cytoplasm. In fact, the presence of Lewy bodies is supposed to be one of the symptoms of Parkinson's disease. Yet, despite the fact that Lewy bodies are also detected in other neurodegenerative diseases, they are not considered to be the specific marker of Parkinson's disease.

The disease is characterized by the occurrence of the pale bodies, i.e. the intracellular granular inclusions, which replace the decaying melanin in the substantia nigra and locus coeruleus. According to the proposed classification of Braak and colleagues, at the asymptomatic stage of Parkinson's disease, Lewy bodies appear in the nerve cells of the olfactory bulb, medulla, and pons. The disease progression and the availability of the pathological cells are observed in the neurons of the substantia nigra, the midbrain, and the basal ganglia. At the final stages, such pathology is observed in the cells of the cerebral cortex.

Parkinson's disease is characterized by four motor disorders, i.e. the tremor, hypokinesia, muscle rigidity, and postural instability, as well as autonomic and mental disorders. The tremor (shaking) is the most obvious and easily detectable of the symptoms.

Parkinson's disease is characterized by tremor, which occurs during rest. However, other types of tremors, such as postural or intentional, may also rarely occur. The frequency of tremor is usually 4.6 Hz (movements per second). It usually begins in the distal part of the one hand. The progression of the disease stimulates the spread of the tremor to the opposite arm and legs.

The multidirectional movements of thumbs and fingers resemble the expense of coins or rolling pills, i.e. there is a similarity with the manual technique of creating pills in the pharmaceutical industry. Sometimes there is also shaking of head of the type yes or no-no, as well as shaking eyelids, tongue, and lower jaw. In rare cases, it covers the whole body. Tremor is enhanced by the excitement and reduces during sleep and voluntary movements.

Hypokinesia implies a reduction in spontaneous motor activity. The patient may freeze for hours while maintaining stiffness. Active movements occur after some delay, however, their rate is slow, i.e. bradykinesia. The patient walks in small steps; feet are parallel with each other, i.e. the puppet gait. The mask-like face, i.e. amimia, frozen look, as well as the rare flashings are also the symptoms of the disease. Smile, the grimace of tears occur belatedly and slowly disappear. The so-called pose of the dummy is supposed to be the main characteristic of Parkinson's disease. The patient's speech has no expression. It is monotone and tends to decay. As a result of the decrease in the range of motion, handwriting became quite small, i.e. micrograph (Tan, Tan, & Fook-Chong, 2003).

One of the manifestations of oligokinesia, i.e. the decrease in the number of movements, is the lack of physiological synkineses. While walking, the patients' hands do not make the usual sweeping movements, but they are pressed against the trunk, i.e. chemokinesis. The compression of the fingers into a fist is not accompanied by the straightening of the hand. The patient cannot perform some purposeful movements at the same time. All actions are looked at as if they were automatic.

The muscle rigidity implies the steady increase in muscle tone on the plastic type. The limbs in their flexion freeze in the set position. The mentioned form of an increase in muscle tone is called plastic waxy flexibility. The prevalence of stiffness in certain groups of muscles leads to the formation of characteristic postures of the petitioner, also known as the dummy posture. The changes in the muscle tone involve the tendency of the limbs to return to their original position after the movement has been done. For example, after sharp passive dorsiflexion of the foot, it retains the position, i.e. the phenomenon of Westphal.

Postural instability develops in the later stages of the disease. The patient has difficulties overcoming the inertia of rest and inertia of motion. The patient is difficult to start moving, and starting it out, it is hard to stop. There are phenomena of propulsion, lateropulsion, and retropulsion. They are expressed in the fact that, while moving forward, to the side or back, the torso usually is ahead of the feet, which results in the disturbing position of the center of gravity. It means that the patient loses stability and falls.

Sometimes patients have paradoxical kinesis. It happens due to the results of the emotional experiences, e.g. after sleep or due to other factors. The person starts to move freely, losing the typical disease symptoms. However, after a few hours, the symptoms return.

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In addition to the disorders of the motor areas, Parkinson's disease is marked with autonomic and metabolic disorders. The result can be either a depletion (cachexia) or obesity. The secretory disorders are manifested in the greasiness of the skin, especially the face, as well as the excessive salivation and sweating (Kempster & Wahlqvist, 2008).


The mental disorders in Parkinson's disease may be the result of the both, i.e. the disease itself and antiparkinsonian drugs. The initial symptoms of psychosis, such as fear, confusion, insomnia, the hallucinatory-paranoid state with disorders in the orientation, are noted in 20% of outpatients and two-thirds of patients with severe Parkinson's disease. 47% of the patients are characterized by depression, while 40% of the patients have sleep disturbances and abnormal fatigue. It causes the fact that the patients are usually sleepy, sluggish, and intrusive, prone to the repentance of the same questions.

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