Parkinson

Parkinson’s disease is a progressive neurological disorder caused by the degeneration (loss of function and cell death) of dopaminergic neurons in the substantia nigra region of the brain. This disease is characterized by a reduction in the production of dopamine, a neurotransmitter critical for coordinating movement. It was first described in 1817 by British physician James Parkinson and named after him at his request. Parkinson’s disease is the second most common neurodegenerative disorder after Alzheimer’s disease and typically affects individuals aged 60 and older; however, it can rarely occur in younger individuals under 40. It is approximately twice as common in men as in women. In Türkiye, it affects 3 per 1,000 individuals over the age of 15 and 2% of those over 65. Globally, it affects approximately 10 million people.

Parkinson’s disease is a subtle and slowly progressing movement disorder that begins with the loss of nerve cells in the brain that produce dopamine. Dopamine is a chemical that enables the brain to regulate and fine-tune movements. Symptoms emerge when 60–80% of the dopaminergic neurons in the substantia nigra region are damaged or lost. The disease typically begins in middle to late life and progresses over a period of 15–25 years. Cases occurring at a young age (5–10%) are often associated with genetic factors. Symptoms usually start on one side of the body and spread to the other side over the years. Parkinson’s disease is not limited to motor symptoms; it also affects quality of life through non-motor symptoms.

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The exact cause of Parkinson’s disease is unknown, but it is believed that the degeneration of dopamine-producing cells is triggered by a combination of genetic and environmental factors. Genetic predisposition plays a significant role, especially in early-onset cases; individuals with a family history of Parkinson’s have a higher risk than the general population. Environmental factors include exposure to chemicals such as pesticides, agricultural chemicals, and manganese, living in rural areas, use of well water, and head trauma (for example, from boxing). Interestingly, studies suggest that smoking and coffee consumption may reduce the risk of Parkinson’s; coffee intake is particularly proposed as a protective factor. Age is one of the most important risk factors; the prevalence of the disease increases significantly after age 60. Additionally, male gender and coexisting conditions such as diabetes may also increase risk.

The symptoms of Parkinson’s disease are divided into two main categories: motor and non-motor, and they vary throughout the course of the disease.

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• Tremor: This is the initial symptom in approximately 60–70% of patients. The tremor typically occurs at rest and is observed in the hands (for example, during the motion of counting money), fingers, arms, legs, jaw, tongue, or lips. It worsens during stress, excitement, or walking, but decreases or disappears with voluntary movement.
• Bradykinesia (Slowness of Movement): It manifests as reduced amplitude of movements, difficulty initiating movement, and inability to perform sequential actions. Daily activities such as buttoning clothes, tying shoelaces, writing, turning in bed, and rising from a chair become difficult. This is a fundamental diagnostic criterion.
• Rigidity: Increased muscle tone causes stiffness in the hands, feet, wrists, elbows, shoulders, and neck. This condition may present early as unilateral shoulder pain.
• Postural and Balance Impairment: Patients develop a stooped posture, walk with small steps, show reduced arm swing, and in advanced stages experience balance loss leading to falls. In later stages, “freezing” episodes (inability to initiate movement) become more frequent.

Beyond motor symptoms, numerous other symptoms significantly affect quality of life. These include loss of smell (an early sign), constipation, sleep disturbances (REM sleep behavior disorder, excessive daytime sleepiness), depression, anxiety, orthostatic hypotension (drop in blood pressure upon standing), urinary incontinence, sexual dysfunction, increased sweating, swallowing difficulties, and in advanced stages, dementia. In early stages, nonspecific complaints such as fatigue, body aches, and difficulty with fine motor tasks are also frequently reported.

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Parkinson’s disease progresses through five stages, with symptom severity increasing and the patient’s level of independence decreasing in each stage:

• Stage One: Symptoms are mild and unilateral. Mild tremor, reduced facial expression (mask-like face), and gait disturbances may be noticed by others. Daily life is unaffected; medication needs are minimal.
• Stage Two: Symptoms become bilateral. Tremor, bradykinesia, and postural changes worsen, but the patient remains independent.
• Stage Three: Balance impairment, slowed reflexes, and falls begin. Daily tasks become more difficult, but the patient can still live independently.
• Stage Four: Movement becomes very slow, walking becomes difficult, and the patient can no longer live alone. Tremor may lessen, but speech difficulties and medication side effects become prominent.
• Stage Five: The patient is confined to a wheelchair or bed. Muscle rigidity is severe, and full-time care is required for all needs.

The diagnosis of Parkinson’s disease is based on the patient’s clinical history and neurological examination; bradykinesia is an essential diagnostic criterion. Brain imaging techniques (MRI, CT) and blood tests are used for differential diagnosis to rule out other causes of parkinsonism such as cerebrovascular disease, tumors, or drug side effects. DaTscan is an imaging technique that uses a radioactive agent to label dopamine cells, facilitating early diagnosis. In Türkiye, it has been available since 2018 in limited centers and is effective in distinguishing Parkinson’s from age-related or depression-related slowing and in predicting disease progression. More advanced methods such as Positron Emission Tomography (PET) and DaT-SPECT are not yet widely used in routine clinical practice.

Although there is no cure for Parkinson’s disease, various methods are used to control symptoms and improve quality of life.

The foundation of treatment consists of drugs that increase dopamine levels. Dopamine precursors and dopamine agonists support dopaminergic transmission in the brain. Medications must be taken lifelong and regularly; abrupt discontinuation can lead to life-threatening risks. Treatment is individualized; a drug effective in one patient may be insufficient in another. Most patients respond well to medication in the first five years, but long-term use may lead to complications such as motor fluctuations (on-off periods), involuntary movements (dyskinesia), and medication resistance.

When medication response declines or side effects become prominent, surgical options are considered. Deep Brain Stimulation (brain pacemaker) regulates movement centers by delivering electrical impulses to the brain. It operates via a generator implanted in the chest wall and functions on a principle similar to a cardiac pacemaker. It is applied in patients under 65 years of age without dementia who initially responded well to medication. The device has a lifespan of 5–6 years and is replaceable. Surgery does not halt disease progression but reduces required medication dosage.

In advanced stages, oral medications are replaced by subcutaneous injections or continuous infusion via a fine tube in the intestine (using a gel-form medication pump). These methods aim to reduce motor fluctuations and dyskinesia.

Physical therapy, exercise, and additional treatments for symptoms such as depression and sleep disorders support the patient’s quality of life. Although foods rich in dopamine such as broad beans are recommended, excessive consumption may trigger involuntary movements.

• Is Parkinson’s genetic? Genetic predisposition is important; risk is higher in those with a family history, but environmental factors are also required.
• How long do patients live? With proper treatment, patients can live 15–25 years or longer; the disease itself is not fatal.
• Is every tremor Parkinson’s? No, tremor at rest that is unilateral is typical, but other causes are possible.
• What should the diet be like? High-fiber foods (to combat constipation), calcium, and vitamin D (to prevent bone loss) are recommended. Antioxidants may be beneficial, but there is no conclusive evidence for vitamin E.
• Is loss of smell observed? Yes, it can be an early symptom.

Parkinson’s disease is an increasingly prevalent health issue as the population ages. In Türkiye, it is estimated that 150,000 to 400,000 individuals have the disease, with approximately 10,000 new diagnoses each year. April 11 is observed as World Parkinson’s Day to raise awareness and promote understanding of the disease. Current research is ongoing into vaccines and genetic therapies. Among neurodegenerative diseases, Parkinson’s responds best to medication and surgery. Early diagnosis is critical for slowing disease progression and extending the duration of high-quality life.

Warning: The content in this article is provided solely for general encyclopedic information purposes. The information here should not be used for diagnosis, treatment, or medical advice. Before making any decisions regarding health, you must consult a physician or qualified healthcare professional. The author and KÜRE Encyclopedia assume no responsibility for any consequences arising from the use of this information for diagnosis or treatment purposes.