Parkinson's disease is a disease that slowly progressive condition resulting from a deficiency in the brain of a chemical called dopamine. Dopamine is one of neurotransmitters in the brain that allow nerve cells to communicate with each other.
People with Parkinson’s disease experience a loss of nerve cells in the part of their brains responsible for controlling voluntary movements. This part of the brain is called the substantia nigra. The nerve cells in the substantia nigra usually produce a chemical called dopamine which helps transmit messages from the brain to the rest of the body via the central nervous system. As these cells are lost, people with Parkinson’s disease experience a loss of dopamine and the messages controlling movement stop being transmitted efficiently.
Over 180 years ago, James Parkinson described a neurodegenerative disease that bears his name.
The term "parkinsonian syndrome" or "parkinsonism" refers to idiopathic Parkinson disease , genetic forms, cases with known environmental causes, and the other atypical forms of parkinsonism, including progressive supranuclear palsy, multiple systems atrophy, and corticobasal degeneration. The latter three are often referred to as "parkinson-plus" syndromes, since each includes features not found in idiopathic Parkinson disease.
The table below shows the classification of Parkinson syndrome.
Distribution of Parkinson Syndromes (PS) | |
Syndrome | % of PS Cases |
Idiopathic PD | 85% |
Neuroleptic-induced | 7%-9% |
MSA | ~2.5% |
PSP | ~1.5% |
Vascular | ~3% |
Known toxins | Very rare |
Recurrent head trauma | Very rare |
From Hughes et al. Neurology. 2001 Nov;57(10 Suppl 3):S34-8.
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DEMOGRAPHICS
Age distribution
D Twelves et al. Systematic review of incidence studies in Parkinson's Disease. Movement Disorders 2003 18: 19-31.
The prevalence rises exponentially with age, after the age of 65. Approximately 0.3% of the general population and 3% of people over the age of 65 have idiopathic Parkinson’s disease diagnosed clinically. About 10% of patients have an onset of disease before the age of 40 - "young-onset" Parkinson's disease
Race
Asians and African blacks have the lowest reported incidence of the disease. To what extent this reflects environmental or genetic differences or differences in ascertainment is not clear, but the prevalence of Lewy bodies in the brains of Nigerians is similar to that of Western populations
Smoking
There is no significant smoking and this disease. It is associated with a lowered risk for the development of Parkinson’s diseaseThe odds ratio of ever having smoked among Parkinson's disease patients compared with the general population was 0.5 about 95%. The implications of this association are not clear.
Rural living
Living in a rural environment has often been associated with an increased risk of idiopathic Parkinson’s disease, possible relating to the influence of pesticide chemicals or consumption of well water. However, the magnitude of this risk in the population of affected individuals is only 10% .
Diet
Diet has been evaluated in many studies to determine if antioxidants present in food protect predisposed patients from the disease. Most of these studies are small or inconclusive. Therefore diet has small percentage that lead to this disease
Genes
A recent large study found high concordance among monozygotic twins when one twin has early-onset disease. Several multigenerational families have been described, with pathologically confirmed Parkinson's disease although in these there are usually atypical features such as rapid rate of progression or a high frequency of dementia. Mutations in 1 exon of the alpha-synuclein gene were recently discovered in a large Italian and 3 smaller Greek families that may have been related and in another exon of the same gene in a German family. However, the disease is rapidly progressive and has a young age onset in these families. Moreover, mutations in this gene have not been found in other families and sporadic IPD. In young-onset Parkinson's disease, the frequency of mutations in the PARKIN gene is high when a first degree family member is also affected. Mutations in this gene were originally described in autosomal recessive Japanese pedigrees with prominent sleep benefit, sensitivity to extrapyramidal side effects of L-DOPA and absence of nigral Lewy bodies in pathologically studied cases. A susceptibility locus on chromosome 2 in familial PD with features more closely resembling sporadic IPD has been described in 6 families with autosomal dominant inheritance with low penetrance .
