Parkinson's Disease: Symptoms & Causes

Parkinson's disease is a progressive, degenerative condition that gradually affects movement, leading to symptoms like shaking (tremors), stiffness, slow movement, and difficulties with walking and balance. It’s thought to result from a mix of genetic and environmental factors, though the exact cause is often unknown.

What Is Parkinson's Disease?

Parkinson's disease (PD) is a progressive neurological disorder that affects movement and other parts of the nervous system. Changes in a part of the brain called the substantia nigra, within the basal ganglia, lead to movement difficulties. PD can also cause non-motor symptoms, affecting various functions beyond movement.

Learn about Parkinson's diagnosis & treatment

In Parkinson's disease, cells in the substantia nigra die or stop working. When that happens, they no longer produce dopamine, an important neurotransmitter. As dopamine levels drop, the chemical balance in the brain is disrupted, leading to neurological symptoms that define Parkinson's disease such as tremors, muscle stiffness, slow movement, and difficulties with balance and coordination.

Parkinson's Disease vs. Parkinsonism

The term “Parkinsonism” or "Parkinsonian syndrome" refers to a group of conditions that share symptoms similar to Parkinson's disease. While Parkinson's disease is the most common, other neurological disorders—such as multiple system atrophy or Lewy body dementia—are also forms of Parkinsonism and can lead to similar symptoms to Parkinson's disease.

The Different Forms of Parkinsonism

• Idiopathic: This refers to Parkinson's disease with no known cause, and it is the most common form.
• Atypical: Some conditions share symptoms with Parkinson’s disease but have additional features. These include conditions like multiple system atrophy, progressive supranuclear palsy, dementia with Lewy bodies, and corticobasal syndrome. These conditions differ from Parkinson’s in their causes, response to treatment, and prognosis.
• Vascular: This occurs when reduced blood flow to the brain, such as after a stroke, causes Parkinson's-like symptoms, such as after a stroke.
• Drug-induced: Some medicines, particularly those used to block the effects of dopamine (such as some treatments for psychological disorders like schizophrenia), can cause Parkinson's-like symptoms. as side effects, usually in cases where the medicine itself is designed to block the effects of dopamine, such as some treatments for psychological disorders like schizophrenia. Unlike other forms, these symptoms typically remain stable and do not worsen over time.

Stages of Parkinson's Disease

A staging system for Parkinson's was first proposed in the 1960s, dividing the disease's progression into five stages. Since then, other systems have been developed that help clinicians assess and treat the disease. The original staging system focused on the patient's level of movement disability. Current rating scales measure PD in terms of how it affects your life, providing doctors with assessment tools to evaluate your symptoms. One of the most common is the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS).

The MDS-UPDRS helps doctors assess how the disease affects movement, thinking, and emotional capabilities, what complications it causes, and how much it affects daily life. These scales are useful in monitoring symptoms but do not predict outcome or prognosis.

Learn more about the stages of Parkinson's disease

Parkinson's Disease Symptoms

The most common symptoms of Parkinson's disease are:

• Tremor (shaking in a part of the body)
• Muscle stiffness
• Slow movement
• Trouble with balance and coordination

You may develop other neurological symptoms. Some of these can occur early in the disease, while others develop as the disease progresses. Other symptoms of Parkinson's include:

• Emotional symptoms, including depression
• Urinary problems or constipation
• Slurred speech or quiet voice
• Difficulty writing
• Problems with automatic movements (drooling, unable to blink, trouble swallowing)
• Trouble thinking clearly or remembering
• Sleep disorders

Physicians at the Mass General Parkinson's Disease Center of Excellence are expertly trained in the diagnosis and treatment of Parkinson’s disease. Learn more by requesting an appointment.

Early Signs of Parkinson's

Often, the early signs of Parkinson's disease are subtle and may not include the movement issues commonly linked to PD. The most common early, or “prodromal,” signs of Parkinson's are sleep disorders, depression, constipation, and loss of smell. As a result, you may not recognize them as Parkinson's symptoms.

Motor symptoms are most people's first clue that they have PD. You may have a very slight tremor in just one small part of the body or swing your arms less when you walk. It's common for one side of the body to be affected more than the other, so, in the early stages of the disease, you may only have symptoms on one side.

What Are the Causes of Parkinson's Disease?

Parkinson’s disease is thought to be caused by a combination of environmental and genetic factors. Most of the time, the specific cause for a person is unknown. In Parkinson’s, a protein called alpha-synuclein, which is normally produced in the body, forms abnormal clumps in brain cells that slowly spread through the nervous system. Research has identified several risk factors for Parkinson's disease, but no clear causal link has been established yet.

Risk Factors for Parkinson's Disease

Known risk factors for developing PD include:

• Age: Early-onset Parkinson's is relatively rare. It most commonly develops in people over the age of 60. Younger patients may need different approaches to treatment, so speak to your doctor about the differences if you're diagnosed at a young age.
• Environment: Repeated exposure to toxins such as pesticides can raise your risk of Parkinson's.
• Family history: A family history of Parkinson's, especially multiple close relatives with the condition, makes you more likely to develop the disease. A small percentage of cases are hereditary (genetic).
• Sex: Parkinson's is more common among biological males. About 60% of people who develop Parkinson’s are males, 40% females.

FAQs about Parkinson's Disease