Parkinson's disease: Symptoms, Causes, Risk Factors, Diagnosis, Stages and Complications

Parkinson's disease is a neurodegenerative disorder of the nervous system that affects movement of your body.

Updated: June 16, 2022

Parkinson's disease is a neurodegenerative disorder of the nervous system that affects movement of your body. Sometimes starts with a barely noticeable tremor in just one hand which could develops gradually causing stiffness or slowing of movement.
Progressive loss of muscle control, which leads to trembling of the limbs and head while at rest, stiffness, slowness, and impaired balance are the Characteristics of Parkinson's disease. The symptoms get worsen as your condition progresses over time and it may become difficult to walk, talk, and complete simple tasks.
The progression of Parkinson's disease and the degree of impairment vary from person to person. Parkinson's disease can affect people much more quickly making them disabled in some cases where as many people with this disease can live long productive lives. Falling related injuries or pneumonia which are the most common complications of this disease can cause premature death.
Onset of Parkinson's disease is most common in adults of 60 years or more. But early onset of the disease between 21 to 40 years and juvenile onset that is before age 21 can also occur. Although the disease can not be cured, medications may help improve your symptoms. In rare cases, surgery may be recommended to regulate certain regions of your brain and improve your symptoms.

Signs and Symptoms of Parkinson's disease:

Symptoms and signs may vary from person to person in Parkinson's disease. The primary symptoms of this disease are all related to voluntary and involuntary motor function and usually start on one side of the body. Early signs may be mild and may go unnoticed, but these will progress over time. Some individuals are more affected than others.This happens due to loss of the dopamine producing cells in the brain. Characteristic motor symptoms include the following:


Trembling or shaking, usually begins in a limb, often in your hand, fingers, arms, feet, legs, jaw, or head. Tremors most often occur while the individual is resting. While involved in a task, it does not occur. Tremors may worsen when an individual is excited, tired, or stressed.


Muscle stiffness may occur in any part of your body. But mostly affected areas are the limbs and trunk, which may increase during movement. Rigidity may produce muscle aches and pain. Loss of fine hand movements can lead to cramped handwriting and may make difficulty in eating.


Slowness of voluntary movement. Over time, it may become difficult to initiate movement and to complete movement making simple tasks difficult and time consuming. Bradykinesia together with stiffness can also affect the facial muscles including blinking, smiling and result in an expressionless, mask like appearance.

Postural instability:

Impaired or lost reflexes can make it difficult to adjust posture to maintain balance. Postural instability may lead to falls.

Parkinsonian gait:

With more progressive Parkinson's disease, people can develop a distinctive shuffling walk with a stooped position. The arm swing will be diminished. It may become difficult to start walking and to make turns. Individuals may freeze in mid stride and appear to fall forward while walking.

Speech changes:

You may have speech problems as a result of Parkinson's disease. You may speak softly, quickly, slur or hesitate before talking. Your speech may be more of a monotone rather than with the usual inflections.
The primary symptoms of Parkinson's disease are mainly movement related. However, overtime the progressive loss of muscle control and continued damage to the brain can lead to secondary symptoms. These vary in severity, and not every individual will experience all of them. Some of the secondary symptoms include:

  • anxiety, insecurity, and stress
  • confusion, memory loss, and dementia which are more common in elderly persons
  • difficulty swallowing and excessive salivation
  • diminished sense of smell
  • increased sweating
  • male erectile dysfunction
  • skin problems
  • constipation
  • depression
  • urinary frequency or urgency

Causes of Parkinson's disease:

Many of the symptoms are due to a loss of certain nerve cells called neurons that produce a chemical messenger in your brain called dopamine. When dopamine levels decrease, it causes abnormal brain activity, leading to signs of Parkinson's disease.
The greater the loss of dopamine, the worse the movement related symptoms. Other cells in the brain also degenerate to some degree and may contribute to non movement related symptoms of Parkinson's disease.
Although lack of dopamine causes the motor symptoms of Parkinson's disease, it is not clear why the dopamine producing brain cells deteriorate. Genetic, certain environmental triggers, various dysfunctional cellular processes, inflammation, and stress can all contribute to cell damage. Several factors that appear to play a role in causing the disease, which include:


Specific genetic mutations that can cause Parkinson's disease which are uncommon. In rare cases with many family members affected by Parkinson's disease, these factor comes in to picture. However, certain gene variations appear to increase the risk of Parkinson's disease. Each of these genetic markers will have a relatively small risk of Parkinson's disease.

Environmental triggers:

Exposure to certain toxins or environmental factors may increase the risk of later Parkinson's disease which is relatively small. Many changes occur in the brains of people with Parkinson's disease. These include:

The presence of Lewy bodies:

Clumps of specific substances called as Lewy bodies within brain cells are microscopic markers of Parkinson's disease. The presence of these substance may cause this disease.

Alpha-synuclein is found within Lewy bodies:

Although many substances are found within Lewy bodies, the presence of natural and widespread protein called alpha-synuclein (A-synuclein) can be a cause of this disease. It is found in all Lewy bodies in a clumped form that cells can't break down.

Risk factors:

Risk factors for Parkinson's disease include:


Generally it begins in middle or late life, and the risk increases with age. People usually develop the disease around age 60 or older.


Having many close relative with Parkinson's disease increases the chances that you will develop the disease.


Men are more likely to develop Parkinson's disease than are women.

Exposure to toxins:

Ongoing exposure to herbicides and pesticides may put you at a slightly increased risk of Parkinson's disease.

Diagnosis of Parkinson's disease:

There is no specific test to diagnose Parkinson's disease. The diagnosis of Parkinson's disease,  especially in the early phase can be challenging due to similarities to related movement disorders and other conditions in many other disease. It is therefore important to re-evaluate individuals in the early phase on a regular basis to rule out other conditions that may be responsible for the symptoms.
A neurologist will diagnose Parkinson's disease based on your medical history, a review of your signs and symptoms, and a neurological and physical examination.
For the medical history, it is important to know whether other family members have Parkinson's disease, what types of medication they have been or are being taken, and whether there was exposure to toxins or repeated head trauma previously.
A neurological exam may include an evaluation of coordination, walking, and fine motor tasks involving the hands. Tests are done to measure mental capacity, behavior, mood, daily living activities, and motor function. These tests can be helpful in the initial diagnosis and to rule out other disorders. These are also used as a measure in monitoring the progression of the disease to make therapeutic adjustments. Certain blood tests can be done, to rule out other conditions that may be causing your symptoms. Imaging tests such as MRI, ultrasound of the brain and PET scans aren't particularly helpful for diagnosing Parkinson's disease. However, these test are used to help rule out other disorders.
In addition to your examination, a Parkinson's disease medication, carbidopa-levodopa is given in a sufficient dose to show the benefit. Significant improvement with this medication will often confirm your diagnosis of Parkinson's disease.
It is recommend to do a regular follow up appointments with neurologists to evaluate your condition and symptoms over time and diagnose Parkinson's disease.
The diagnosis of Parkinson's disease is more likely if:

  • at least two of the three major symptoms such as tremor at rest, muscle rigidity, and slowness are present
  • the onset of symptoms started on one side of the body
  • symptoms are not due to secondary causes such as medication or strokes in the area controlling movement
  • symptoms are significantly improved with levodopa.

Stages of Parkinson's disease:

The stages reflect the increasing severity of the disease. These are categorized in to:

  • Stage 1: mild symptoms of tremors and/or movement symptoms like swinging arm while walking. These do not interfere with daily activities and occur on one side of the body.
  • Stage 2: Symptoms worsen with walking problems and both sides of the body are affected.
  • Stage 3: Symptoms worsen with loss of balance and slowness of movement.
  • Stage 4: Severity of symptoms require help of others. Usually the person cannot do his/her activities of daily routine.
  • Stage 5: Caregiver is needed for all activities. The individual may not be able to stand or walk, and may be bedridden, and have hallucinations and delusions.

Complications of Parkinson's disease:

The complications are often accompanied by this disease which include:

Depression and emotional changes:

People with Parkinson's disease may experience depression. Depression can be treated and the medications can make it easier to handle the other challenges of Parkinson's disease.You may also experience other emotional changes, such as fear, anxiety or loss of motivation. These symptoms can also be treated by medications.

Thinking difficulties:

You may experience cognitive problems or dementia and thinking difficulties. Usually this occur in the later stages of Parkinson's disease. These are not treatable as cognitive problems aren't very responsive to medications.
Swallowing problems:
As your condition progresses, you may develop difficulties with swallowing. Saliva may accumulate in your mouth due to slowed swallowing, leading to drooling.

Bladder problems:

Bladder problems, including being unable to control urine or having difficulty urinating can occur.


Due to a slower digestive tract, many people with Parkinson's disease develop constipation.

Sleep problems and sleep disorders:

People with Parkinson's disease often have sleep problems, including waking up frequently throughout the night, waking up early or falling asleep during the day.
People may also experience rapid eye movement sleep behavior disorder, which involves acting out your dreams. Medications may help your sleep problems.

Blood pressure changes:

Due to a sudden drop in blood pressure known as orthostatic hypotension, you may feel dizzy or lightheaded when you stand.

Smell dysfunction:

You can develop problems with your sense of smell. You may have difficulty identifying certain odors or the difference between odors.


Many people with Parkinson's disease lose energy and experience fatigue.


You may experience pain, which could be either in specific areas of your body or throughout your body.

Sexual dysfunction:

Some people with Parkinson's disease will have a decrease in sexual desire or performance.

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