- What is Parkinson’s Disease
- Statistics on Parkinson’s Disease
- Risk Factors for Parkinson’s Disease
- Progression of Parkinson’s Disease
- Symptoms of Parkinson’s Disease
- Clinical Examination of Parkinson’s Disease
- How is Parkinson’s Disease Diagnosed?
- Prognosis of Parkinson’s Disease
- How is Parkinson’s Disease Treated?
- Parkinson’s Disease References
What is Parkinson’s Disease
Parkinson’s disease involves a depletion of dopamine-containing neurons in the substantia nigra of the basal ganglia in the brain. The classical features of Parkinson’s disease include resting tremor, rigidity, bradykinesia (slowness) and postural instability. This cluster of symptoms is referred to as Parkinsonism syndrome, which can be caused by other neurodegenerative disorders, cerebrovascular disease and certain drugs.
Statistics on Parkinson’s Disease
The incidence and prevalence of Parkinson’s disease is uniform throughout the world. It generally commences in middle or late life, affecting 1-2 per 1,000 of the general population, and up to 2 per 100 people over 65 years. Parkinson’s disease affects all ethnic groups. Males and females are equally affected. Approximately 78,000 Australians are affected by Parkinson’s disease.
Risk Factors for Parkinson’s Disease
The cause of Parkinson’s disease is unknown. Many cases are described as idiopathic or sporadic Parkinson’s disease (meaning they occur quite randomly in patients with no known predisposing factors). However, certain risk factors have been identified:
- Non-smokers – Studies have shown Parkinson’s disease to be less prevalent in tobacco smokers than in non-smokers.
- Herbicides such as methylphenyltetrahydropyridine (MPTP) may be associated with Parkinson’s disease.
- Encephalitis lethargica – Survivors of this disease develop severe Parkinsonism.
- Genetic factors – Some families will have multiple cases of early-onset Parkinson’s, but the majority of cases are non-familial.
Parkinsonism (the syndrome of rigidity, slowness and tremor) can be induced by drugs (reserpine, phenothiazines), and is seen in neurodegeneration, arteriosclerosis, carbon dioxide poisoning, Wilson’s disease, multi-system atrophy, communicating hydrocephalus and progressive supranuclear palsy (another illness causing rigidity and problems with eye movements and speech). Drinking moderate amounts of coffee, smoking, using non-steroidal anti-inflammatory drugs (NSAIDs) and oestrogen replacement in postmenopausal women (HRT) may actually reduce your incidence of Parkinson’s disease.
Progression of Parkinson’s Disease
Parkinson’s disease does not affect everyone the same way. In some people the disease progresses quickly, in others it does not. Although some people become severely disabled, others experience only minor motor disruptions. Tremor is the major symptom for some patients, while for others tremor is only a minor complaint and different symptoms are more troublesome.
Symptoms of Parkinson’s Disease
Parkinson’s disease can have a variable onset. The typical first symptom is a tremor in one of the hands. You may also notice clumsiness in some of your movements. Over time you may notice your movements becoming slower and more rigid, and you have increasing difficulty walking. The common symptoms of Parkinson’s include:
- Tremor: Typically worse during stress and absent or reduced during sleep.
- Aching stiff joints and limbs.
- Difficulty with fine movements.
- Bradykinesia: You may have difficulty in initiating movement (e.g. starting to walk or rising from a chair).
- Dribbling saliva, dysphagia (difficulty swallowing), constipation and depression. In the later stages, you may develop dementia and personality changes.
Your doctor will ask you detailed questions about your symptoms and their course to determine whether they fit the classical picture of Parkinson’s disease. He or she will also ask questions about your family and a number of lifestyle factors to determine whether you are predisposed to this condition. There is no clear test to determine whether you have Parkinson’s, so doctors base the diagnosis on clinical features. Asymmetry of symptoms, presence of resting tremor and good response to dopamine replacement therapy all suggest Parkinson’s disease.
Clinical Examination of Parkinson’s Disease
Your doctor will carefully examine you, looking for the three cardinal signs of Parkinson’s disease. These are resting tremor, rigidity, and bradykinesia (only two of these are needed to make the diagnosis). In order to do this, your doctor will assess your gait (walking), observe you resting, feel the tone in your limbs and ask you to perform a number of movements. In addition, your doctor may ask a series of questions to assess your mental state and memory. The main signs looked for on examination include:
- Tremor: Characteristically a 4-6 Hz resting tremor of the hands. It appears as a pill-rolling movement between the thumb and forefinger. The tremor is improved by voluntary movement and made worse by anxiety.
- Rigidity (increase in resistance to passive movement about a joint): This may be smooth (lead-pipe) or oscillating due to interruption of the increased tone with tremor (cog-wheel). Your doctor will try to test the rigidity by passively moving one arm whilst you perform a task with the other arm.
- Bradykinesia: Your doctor may notice a reduction in spontaneous movements and fidgeting. You may also have reduced facial expressions, less blinking, small handwriting and slow, soft speech.
- Stooped posture
- Narrow-based, hurrying and shuffling gait with lack of arm swinging.
- Mental state examination may reveal evidence of dementia and impaired memory or concentration. These changes are seen in over half of patients over 65 years.
How is Parkinson’s Disease Diagnosed?
Diagnosis of Parkinson’s disease is largely clinical, so in typical cases no investigations will be ordered. However, if your presentation shows atypical features (early onset, bilateral symptoms at onset, lack of tremor, etc), your doctor may order additional tests to exclude other causes of the symptoms. This may include CT, MRIs, PET scans or copper studies as appropriate.
Prognosis of Parkinson’s Disease
There is no cure for Parkinson’s disease. Initially treatment can produce good symptom control, however, the disease gradually progresses over 10-15 years, and death results from infection in most cases. Occasionally the patient may live for several decades after the onset of the disease. To date, no treatment has been found to reliably alter the prognosis of Parkinson’s disease,
How is Parkinson’s Disease Treated?
Although no medications will alter the course of Parkinson’s disease, they can give effective symptomatic relief. Medications should only be used when they are necessary, as their effect declines over time, even with increased doses, and they also produce unwanted side effects. A wide range of drugs are currently available for treating Parkinson’s disease. Many of these are types of dopamine replacement therapy, which replaces the deficient dopamine within the substantia nigra in the brain. Levodopa is the best treatment for Parkinson’s disease and is often used in combination with a peripheral decarboxylase inhibitor (L-dopa plus carbidopa, or L-dopa plus benserazide). This combination reduces the dose of L-dopa required, and thus reduces peripheral side effects. Other treatments:
- Bromocriptine: A dopamine agonist. There are also other dopamine agonists, but their role is uncertain (caberfoline, rapinirole).
- Selegiline: A type-B monoamine oxidase inhibitor that inhibits dopamine catabolism in the brain.
- Amantadine: Increases synthesis and release of dopamine and has a weak antiparkinsonian effect.
- Anticholinergic drugs: Will reduce tremor but have little effect on bradykinesia.
Your doctor will decide which medications are best for you based on your age and particular symptoms. In young patients, levodopa therapy is often delayed and patients are started on dopamine agonists. This is because effects of levodopa wear off over time, while dopamine agonists are effective and have fewer motor fluctuations. If you are older than 70 you may be commenced on levodopa medications straight away. Depression frequently occurs with Parkinson’s disease, but it is generally recommended to avoid antidepressant medications as they can worsen symptoms. In particular, certain drugs called monoamine oxidase inhibitors (MAOIs) are contraindicated in patients receiving levodopa drugs. Some surgical options are available for Parkinson’s disease, such as deep brain stimulation. These have shown promise for patients with advanced disease with motor fluctuations. However, they are still largely experimental and very expensive. You will also have input from a variety of multidisciplinary services, such as occupational therapy, speech pathology, physiotherapy, dietetics, social work and counselling. These services will help to overcome some of the particular problems encountered with Parkinson’s disease in your daily life.
|For more information on the latest medical advances being used in the treatment of advanced Parkinson’s Disease (PD) including the use of Deep Brain Stimulation (DBS), see New treatments for advanced Parkinson’s disease.|
|For more information on neurological disorders that affect movement, and their treatments, see Neurological Rehabilitation and Movement Disorders.|
Parkinson’s Disease References
- Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison’s Principles of Internal Medicine. 15th Edition. McGraw-Hill. 2001
- Cotran, Kumar, Collins 6th edition. Robbins Pathologic Basis of Disease. WB Saunders Company. 1999.
- Fung V, Morris J & Pell M. Surgical treatment for Parkinson’s disease. MJA 2002 177(3): 125-6.
- Haslet C, Chiliers ER, Boon NA, Colledge NR. Principles and Practice of Medicine. Churchill Livingstone 2002.
- Hauser R, Pahwa R. Parkinson Disease. eMedicine, Web MD, 2006. Available from: [URL Link]
- Hurst JW (Editor-in-chief). Medicine for the practicing physician. 4th edition Appleton and Lange 1996.
- Kumar P, Clark M. Clinical Medicine. WB Saunders 2002 Pg 427-430.
- Longmore M, Wilkinson I, Torok E. Oxford Handbook of Clinical Medicine. Oxford Universtiy Press. 2001.
- Quin N. Fortnightly review: Drug treatment of Parkinson’s disease. BMJ 1995; 310: 575-9.