|Illustration of the Parkinson disease by Sir William Richard Gowers from A Manual of Diseases of the Nervous Systemin 1886|
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Parkinson’s disease (also known as Parkinson disease or PD) is a degenerative disorder of the central nervous system that often impairs the sufferer’s motor skills and speech.
Parkinson’s disease belongs to a group of conditions called movement disorders. It is often characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia), and in extreme cases, a loss of physical movement (akinesia). The primary symptoms are the results of excessive muscle contraction, normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level cognitive dysfunction and subtle language problems. PD is both chronic, meaning it persists over a long period of time, and progressive.
PD is the most common cause of parkinsonism, a group of similar symptoms. PD is also called “primary parkinsonism” or “idiopathic PD” (“idiopathic” meaning of no known cause). While most forms of parkinsonism are idiopathic, there are some cases where the symptoms may result from toxicity, drugs, genetic mutation, head trauma, or other medical disorders.
Symptoms of Parkinson’s disease have been known and treated since ancient times. However, it was not formally recognised and its symptoms were not documented until 1817 in An Essay on the Shaking Palsy by the British physician James Parkinson. Parkinson’s disease was then known as paralysis agitans. The underlying biochemical changes in the brain were identified in the 1950s, due largely to the work of Swedish scientist Arvid Carlsson who later went on to win a Nobel Prize. L-dopa entered clinical practice in 1967, and the first study reporting improvements in patients with Parkinson’s disease resulting from treatment with L-dopa was published in 1968.
Parkinson’s disease is widespread, with a prevalence estimated between 100 and 250 cases per 100,000 in North America; globally prevalence estimates range from a low of 15 per 100,000 in China to a high of 657 per 100,000 in Argentina. Because prevalence rates can be affected by socio-ecomically driven differences in survival as well as biased by survey technique problems  , incidence is a more sensitive indicator: rates have ranged from 1.5 per 100,000 in China to a high of 14.8 per 100,000 in Finland. Incidence has been estimated by several groups. A study carried out in northern California observed an age and sex corrected incidence of 13.4 per 100,000/year. The study authors noted a rapid increase in incidence with age, male rates nearly double female rates, and an elevated rate amongst Hispanics. A study in Spain (of a population of people aged 65 to 85) calculated incidence, adjusted for age and sex, of 186.8/100,000 per year, with men’s rates being 2.55 times that of women. For the same age group, the northern California study observed an incidence of roughly 120/100,000/year. A Dutch study, published in the same year, noted age-specific incidence rates from 0.3 per 1000 person-years in subjects aged 55 to 65 years, to 4.4 per 1000 person-years for those aged ≥85 year, and a sex ratio of 1.55 for male incidence.
Cases of PD are reported at all ages, though it is quite rare in people younger than 40 and the average age at which symptoms begin is 58-60; it is principally a disease of the elderly. It occurs in all parts of the world, but appears to be more common in people of European ancestry than in those of African ancestry. Those of East Asian ancestry have an intermediate risk. It is more common in rural than urban areas and men are affected slightly more often than women. It is highly unusual for people under 40 to develop Parkinson’s Disease, and twin studies (Tanner). have shown such disease to be almost entirely genetically caused.
There are other disorders that are called Parkinson-plus diseases. These include:
- Multiple system atrophy (MSA)
- Shy-Drager syndrome (SDS)
- Striatonigral degeneration (SND)
- Olivopontocerebellar atrophy (OPCA)
- Progressive supranuclear palsy (PSP)
- Corticobasal degeneration (CBD)
Some people include dementia with Lewy bodies (DLB) as one of the ‘Parkinson-plus’ syndromes. Although idiopathic Parkinson’s disease patients also have Lewy bodies in their brain tissue, the distribution is denser and more widespread in DLB. Even so, the relationship between Parkinson disease, Parkinson disease with dementia (PDD) and dementia with Lewy bodies (DLB) might be most accurately conceptualized as a spectrum, with a discrete area of overlap between each of the three disorders. The natural history and role of Lewy bodies is very little understood.
Patients often begin with typical Parkinson’s disease symptoms which persist for some years; these Parkinson-plus diseases can only be diagnosed when other symptoms become apparent with the passage of time. These Parkinson-plus diseases usually progress more quickly than typical ideopathic Parkinson disease. The usual anti-Parkinson’s medications are typically either less effective or not effective at all in controlling symptoms; patients may be exquisitely sensitive to neuroleptic medications like haloperidol. Additionally, the cholinesterase inhibiting medications have shown preliminary efficacy in treating the cognitive, psychiatric, and behavioral aspects of the disease, so correct differential diagnosis is important.
Wilson’s disease (hereditary copper accumulation) may present with parkinsonistic features; young patients presenting with parkinsonism may be screened for this rare condition. Essential tremor is often mistaken for Parkinson’s disease but usually lacks all features besides tremor.
PD is not by itself a fatal disease, but it does get worse with time. The average life expectancy of a PD patient is generally lower than for people who do not have the disease. In the late stages of the disease, PD may cause complications such as choking, pneumonia, and falls that can lead to death.
The progression of symptoms in PD may take 20 years or more. In some people, however, the disease progresses more quickly. There is no way to predict what course the disease will take for an individual person. One commonly used system for describing how the symptoms of PD progress is called the Hoehn and Yahr scale.
Another commonly used scale is the Unified Parkinson’s Disease Rating Scale (UPDRS). This much more complicated scale has multiple ratings that measure mental functioning, behavior, and mood; activities of daily living; and motor function. Both the Hoehn and Yahr scale and the UPDRS are used to measure how individuals are faring and how much treatments are helping them. It should be noted that neither scale is specific to Parkinson’s Disease; that patients with other illnesses can score in the Parkinson’s range.
With appropriate treatment, most people with PD can live productive lives for many years after diagnosis.
Notable Parkinson’s sufferers
One famous sufferer of young-onset Parkinson’s is Michael J. Fox, who has written a book about his experience of the disease and established The Michael J. Fox Foundation for Parkinson’s Research to develop a cure for Parkinson’s disease within this decade.
Other famous sufferers include Pope John Paul II, playwright Eugene O’Neill, artist Salvador Dalí, evangelist Billy Graham, former US Attorney General Janet Reno, boxer Muhammad Ali, dictators Adolf Hitler, Franco and Mao Zedong, and numerous actors such as Terry-Thomas, Deborah Kerr, Kenneth More, Vincent Price and Michael Redgrave.
The film Awakenings (starring Robin Williams and Robert De Niro and based on genuine cases reported by Oliver Sacks) deals sensitively and largely accurately with a similar disease, postencephalitic parkinsonism.
- This article contains text released into the public domain from:
National Institute of Neurological Disorders and Stroke (January 2006). Parkinson’s Disease: Hope Through Research. National Institutes of Health.
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- National-level and International Organisations
- American Parkinson Disease Association
- European Parkinson’s Disease Association
- National Parkinson Foundation (US)
- Parkinson Society Canada
- Parkinson’s Disease Society (UK)
- Parkinson’s Disease Foundation (US)
- Parkinson’s Action Network (US)
- Parkinsons Research Foundation (US)
- World Parkinson Disease Association
- Other sites
- Parkinson’s Disease at the Open Directory Project