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Parkinson's disease - symptoms, causes, treatment

 
Parkinson’s disease is a progressive, degenerative disorder of the brain. Symptoms include tremors, stiffness or rigidity, and slowness of movement (bradykinesia).
 
According to Parkinson’s New Zealand, approximately 1% of people over the age of 60 have the condition. Various theories exist regarding causes of the disease. There is no cure for Parkinson’s disease so treatment will normally focus on managing symptoms, typically with medication.

Signs and symptoms

The 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.
 
Brain scan 1Stiffness
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.
 
Bradykinesia
This means slowness of movement and 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. Bradykinesia can also make the face seem flat or expressionless.
 
Loss of Balance
This is a symptom that tends to develop later in Parkinson’s disease.  Because of impaired balance and co-ordination (postural instability) a person with Parkinson’s disease can develop a forward or backward lean.  They may start to walk with small steps as if hurrying forward to keep balance (festinations).  Frequent falls are also common.
 

Other symptoms that may be experienced include:  

  • Skin sensations and pain
  • Constipation
  • Bladder problems
  • Sexual dysfunction
  • Sleep problems
  • Fatigue
  • Depression
  • 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 occurs as the result of insufficient quantities of the neurotransmitter dopamine in a part of the brain called the substantia nigra. The substantia nigra helps in the planning and programming of movement. A neurotransmitter is a chemical substance that is released from the ends of neurones (nerve cells) to communicate with one or several other neurones. Dopamine levels are reduced as the neurones that produce dopamine die. As a result, messages concerning the planning and programming of movement are interrupted.
 
It is not known why this occurs 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 an internal or external toxin affects the body’s ability to produce dopamine.
 
Accelerated ageing
One theory is that in some individuals, for some unknown reason, the normal, age-related death of the neurones that produce dopamine is accelerated.
 
Free Radicals
Some researchers believe that the neurones 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
  • 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 very 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.  The neurologist may need to observe the person for some time as Parkinson’s disease does not usually occur suddenly. 
 

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 does 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.

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 provide dramatic results and there are a number that can be prescribed.   The two mediations 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 decrease and it can also cause unwanted side effects such as nausea and involuntary movements (dyskinesias).  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: this class of medication (eg: entacapone) 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.
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 allowing the person with Parkinson’s disease to feel more confident and capable.
 
Brain surgery
Surgery, while not commonly performed, may be appropriate in cases of very severe tremor or involuntary movements that cannot be adequately controlled with medication.  This is done 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.  The implanted electrode, controlled by a pacemaker-like device implanted under the skin below the collar bone, generates electrical currents that disrupt signals from the brain that cause tremors.  The surgery is major and can take over eight hours.  DBS is not a cure and the crtieria for selection of patients appropriate for the surgery are very 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.  The response of the body to dopamine also seems to improve with exercise.  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.  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.  In addition, the brain recharges its dopamine overnight.
 
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.
 
Alternative treatments
Treatments such as massage, acupuncture and yoga have proved helpful in relieving symptoms in some people.  Vitamin, mineral and herbal remedies may also prove beneficial in some cases.  It is important to discuss the use of any alternative therapies with the doctor, as some of these therapies may interact with conventional treatments.

Further support

For more information on Parkinson’s disease contact your doctor or Parkinsons 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. (2016). Parkinson disease (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. http://emedicine.medscape.com/article/1831191-overview [Accessed: 11/07/17]
O'Toole, M.T. (Ed.) (2013) Parkinson's disease. Mosby's Dictionary of Medicine, Nursing & Alllied Health Professionals (9th Ed.). St Louis: Elsevier Mosby.
Parkinson's New Zealand (2015). Medications used in the treatment of Parkinson’s: A guide for people with Parkinson's and those who care for them (Booklet). Wellington: Parkinson’s New Zealand. http://www.parkinsons.org.nz/sites/default/files/10693%20PSNZ%20Medication%20Booklet%20PDF.pdf
Parkinson's New Zealand. (Date Unknown). What is Parkinson's? (Web Page). Wellington: Parkinson’s New Zealand. http://www.parkinsons.org.nz/what-parkinsons [Accessed: 11/07/17]
 
Last reviewed - July 2017
 
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