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Parkinson's disease - symptoms, causes, treatment

 

Parkinson’s disease is a disorder of the brain that gets worse over time. Symptoms include tremors, stiffness or rigidity, and slowness of movement. 

There is no cure for Parkinson’s disease so treatment will normally focus on managing symptoms, typically with medication.

Approximately 1% of New Zealanders over the age of 60 years have the condition.

Signs and symptoms

Brain scan 1The distinctive symptoms of Parkinson’s disease include:

Tremor 
Most people with Parkinson’s disease develop a tremor that is most prominent in the hands and fingers. It tends to occur when the limb is relaxed (a resting tremor), disappearing when performing tasks such as drinking or eating. Some people with Parkinson’s disease never develop a tremor.

Stiffness 
Stiffness or rigidity is a common early sign of Parkinson’s disease and is most obvious in the arms, shoulder, or neck, although it can occur in all muscle groups. People may have difficulty getting out of a chair, turning or rolling over in bed, or walking. Fine finger movements such as doing up a button or tying a shoelace may also be difficult. Pain or a deep aching sensation in the muscles may also be felt. 

Slow movement (bradykinesia)
Slowness of movement is a disabling and frustrating symptom of Parkinson’s disease. People have difficulty initiating movement and movement may be slow. There may also be a lack of coordination when moving and normal activities can prove difficult. Activities once performed quickly and comfortably, such as washing or dressing, may take several hours if not assisted. Slowness of movement can also make the face seem flat or expressionless.

Loss of Balance
This is a symptom that tends to develop over time. Because of impaired balance and coordination (postural instability) a person with Parkinson’s disease can develop a forward or backward lean. They may start to walk with small shuffling steps as if hurrying forward to keep balance (known as festinating gait or Parkinsonian gait). Falls are also common.

Other symptoms that may be experienced include: 

  • Skin sensations and pain
  • Constipation
  • Bladder problems
  • Sexual dysfunction
  • Sleep problems
  • Fatigue
  • Depression
  • Soft voice
  • Altered speech (may be slurred and slow)
  • Difficulty with writing
  • Numbness
  • Walking difficulty
  • Dementia (impaired memory, concentration, judgement)
  • Decreased blinking
  • Increased saliva production
  • Emotional changes.

Causes

Parkinson’s disease is the result of losing nerve cells in a part of the brain that helps with the control and co-ordination of movement.  These nerve cells are responsible for producing a chemical called dopamine that helps nerve cells communicate; reduced dopamine levels mean that part of the brain cannot function normally, causing movements to become slow and abnormal. 

It is not known why dopamine-producing nerve cells die but several possible causes have been studied:

Genetic factors
Specific gene mutations that can cause Parkinson's disease have been identified but these are uncommon, except in rare cases with many family members affected by Parkinson's disease. There also exist certain gene variations that appear to increase the risk of Parkinson's disease.

Environmental toxins
Despite no conclusive evidence that this is a cause, some scientists believe that exposure to pesticides, herbicides, and insecticides may be associated with the development of Parkinson’s disease. 

Accelerated ageing
One theory is that in some individuals, for some unknown reason, the normal, age-related death of the nerve cells that produce dopamine is accelerated.

Free Radicals
Some researchers believe that the nerve cells that produce dopamine die due to the activity of free radicals. Free radicals are potentially-damaging molecules produced in the body during normal chemical reactions.

Lewy bodies
Many changes occur in the brains of people with Parkinson's disease. One of these changes is the presence of Lewy bodies, which are abnormal clumps of protein within brain cells. Lewy bodies are believed to hold an important clue to the cause of Parkinson's disease. 

Risk factors

Apparent risk factors for developing Parkinson’s disease include: 

  • Age 
  • Male gender
  • Family history of Parkinson’s 
  • Extreme stress
  • Head trauma 
  • Caucasian ancestry 
  • Herbicide/pesticide exposure 
  • Rural residence
  • Higher intake of dietary fats.

Several factors have also been associated with a decreased risk and include: 

  • Cigarette smoking 
  • Higher caffeine intake
  • Anti-oxidants in diet
  • Early-life measles infection.

Diagnosis

There is a no single test to diagnose Parkinson’s disease. In its early stages, a diagnosis of Parkinson’s disease can be difficult even for an experienced doctor. For example, the tremor in Parkinson's disease is similar to that of a less severe form of movement disorder known as essential tremor

If Parkinson’s disease is suspected, a referral to a neurologist (nervous system specialist) may be recommended. 

A diagnosis is based on: 

  • A person’s medical history
  • Observing symptoms 
  • A neurological and physical examination — this may involve the use of imaging techniques such as computerised tomography (CT) or magnetic resonance imaging (MRI) to rule out other conditions. 
  • A trial dose of carbidopa-levodopa, a Parkinson's disease medication, may be given. A significant improvement in symptoms with this medication will often confirm a diagnosis of Parkinson's disease.

A diagnosis of Parkinson’s disease usually requires the presence of two of the three main symptoms: tremor, stiffness and slow movement.

Treatment

Parkinson’s disease cannot be cured so treatment focuses on managing symptoms. Several treatments are used in the management of Parkinson’s disease. These include:

Medications 

Medications can produce dramatic results and there are a number that can be prescribed. The two medications most commonly used to help control symptoms are: 

Carbidopa-levodopa:
Levodopa has proven to be an effective treatment for many people. Levodopa is converted to dopamine within the brain, reducing many of the disabling symptoms of Parkinson’s disease. Over time the effect of levodopa can wane and it can also cause unwanted side effects such as nausea and involuntary movements. For this reason, it may be avoided in the early stages of the condition. Levodopa is combined with carbidopa to protect against premature conversion of the levodopa to dopamine outside of the brain, which prevents or lessens side effects.

Dopamine agonists:
Whereas levodopa artificially replaces dopamine in the brain, dopamine agonists mimic the effects of the lost dopamine. They can be used alone or in combination with levodopa. Dopamine agonists can remain effective for several years and avoid some of the unwanted side-effects of levodopa.

Catechol-O-methyltransferase (COMT) inhibitors:
Given together with carbidopa/levodopa, this class of medication mildly prolongs the effect of levodopa therapy by blocking an enzyme that breaks down dopamine.

Amantadine:
This drug may be prescribed alone to provide short-term relief of symptoms of mild, early-stage Parkinson's disease. It may also be given with carbidopa-levodopa during the later stages of Parkinson's disease to control involuntary movements caused by levodopa.

MAO-B inhibitors:
These medications can help relieve symptoms in the early stages of Parkinson’s disease.

Physiotherapy 

Mobility, co-ordination, range of motion, and muscle tone can all be improved with physiotherapy. Increasing muscle strength and improving gait and balance also helps prevent falls, which helps a person with Parkinson’s disease to feel more confident and capable. 

Occupational therapy

By modifying home and work environments and providing aids for mobility, an occupational therapist can assist people with Parkinson’s disease to maintain their independence. 

Speech therapy

Some people with Parkinson’s have difficulty projecting their voice or develop slurred or stuttering speech. A speech therapist can help people with Parkinson’s disease to improve their communication.

Brain surgery

Surgery, while not commonly performed, may be appropriate in cases of severe tremor or involuntary movements that cannot be adequately controlled with medication. Brain surgery as a treatment for Parkinson’s disease is performed by a specialist neurosurgeon.

In recent years deep brain stimulation (DBS) has become the main surgical option for Parkinson's disease. It involves implanting a small electrode into a specific area of the brain to  electrically disrupt signals that cause tremors. The surgery is major and can take over eight hours. DBS is not a cure and the criteria for selection of patients appropriate for the surgery are strict.

Self-help measures

A range of self-help strategies can help improve the quality of life of a person with Parkinson’s disease. These include:

Exercise
Movement is affected in Parkinson’s disease and exercise can improve mobility and general health. Parkinson's New Zealand suggests that people with the disease aim to get at least 20–30 minutes each day of aerobic exercise, such as walking.

Sleep
Sleep is important to Parkinson’s disease sufferers, in part because the brain recharges its dopamine overnight. Most people with the disease tend to feel better in the morning and deteriorate during the day. Many also find that having a good day is related to having had a good night’s sleep. 

Diet
It is important to eat a nutritionally-balanced diet. However, no specific diet has been shown to be of therapeutic value in Parkinson’s disease. 

Further support

For more information on Parkinson’s disease contact your doctor or Parkinson's New Zealand.

Parkinson's New Zealand
Phone: 0800 473 4636 (0800 4 PD INFO)
E-mail: info@parkinsons.org.nz
Website: www.parkinsons.org.nz 

References

Hauser, R.A. (2020). Parkinson disease (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/1831191-overview [Accessed: 16/06/20] 
O'Toole, M.T. (Ed.) (2017) Parkinson's disease. Mosby's Dictionary of Medicine, Nursing & Allied Health Professionals (10th Ed.). St Louis: Elsevier. 
Parkinson's New Zealand (2018). Parkinson’s. A guide for the newly diagnosed (Booklet PDF). Wellington: Parkinson’s New Zealand. https://www.parkinsons.org.nz/sites/default/files/2019-01/Newly%20Diagnosed%20WEB%202.pdf 
Parkinson's New Zealand. (Date not stated). What is Parkinson's? (Web Page). Wellington: Parkinson’s New Zealand. https://www.parkinsons.org.nz/understanding-parkinsons/what-parkinsons [Accessed: 16/06/20]

Last reviewed – June 2020

 
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