Parkinson's disease is the most common neurodegenerative disease after Alzheimer's and the first cause of parkinsonian syndrome.
Parkinson's disease is the 2nd most common neurodegenerative disease after Alzheimer's disease. It currently affects 270,000 people in France, with the number of new cases rising steadily each year as the population ages.
The most important risk factor for developing Parkinson's disease is age, with a prevalence of 0.04% in people aged between 40 and 49, rising to 2% in the over-80s.
Men are more affected than women, with a ratio of 2 men to 1 woman after the age of 40.
Parkinson's disease is characterised by degeneration of the dopaminergic neurons in the substantia nigra of the brain, located in a particular region of the brain stem and composed mainly of dopamine neurons. Other regions may also be affected, resulting in ‘non-motor’ disorders such as sleep disorders, blood pressure disorders or, later on, walking disorders, each of which corresponds to different neuronal circuits.
From a symptomatic point of view, the best-known clinical signs of the disease are resting tremors, but the most frequent and characteristic are slowness of movement or akinesia and muscular rigidity.
Most treatments are aimed at improving symptoms and slowing the progression of the disease.
The causes of Parkinson's disease
5% of cases of Parkinson's disease are familial, i.e. inherited through mutation of a dominant or recessive gene. To date, 13 genes have been identified as causative in this disease.
Other cases are sporadic, in which the disease develops following exposure to an environmental factor in genetically predisposed individuals. Parkinson's disease, like many neurological diseases, is said to be multifactorial. Numerous environmental factors and genetic predisposition factors conferring a higher risk of developing the disease have been identified in recent years.
Find out more about the Brain Institute's research on the page dedicated to the causes of Parkinson's disease.
The biological mechanisms of Parkinson's disease
The main molecular player in Parkinson's disease is a protein expressed in neurons called α-synuclein. During the course of the disease, this protein pathologically aggregates to form clusters known as Lewy bodies. This phenomenon occurs mainly in the dopaminergic neurons of the substantia nigra, a region located in the brain stem, but also appears in other areas of the brain during Parkinson's disease. The death of neurons linked to a-synuclein aggregates leads to a deficit in the production of neurotransmitters, the molecules that enable communication between neurons, triggering the onset of symptoms.
Find out more about the Institut du Cerveau's research on the page dedicated to the biological mechanisms of Parkinson's disease.
Symptoms, diagnosis and course of Parkinson's disease
The symptoms observed in Parkinson's patients are caused by damage to the substantia nigra and striatum, followed by other brain regions.
The 1st symptoms that lead to a diagnosis of Parkinson's disease are akinesia (slowness of movement), muscular hypertonia (stiffness of the muscles) and tremors at rest that disappear during a voluntary movement. These symptoms together constitute the Parkinson's syndrome.
The diagnosis of Parkinson's disease is based on the demonstration of a pure, asymmetric parkinsonian syndrome that is sensitive to dopaminergic treatment.
Treatments for Parkinson's disease
The aim of the treatments prescribed to Parkinson's patients is to compensate for the dopamine deficit inherent in neuronal death. There are two types of treatment:
- L-DOPA, a dopamine precursor molecule capable of crossing the blood-brain barrier, which is converted into dopamine in the brain.
- Dopaminergic agonists, molecules with the same effect as dopamine.
These two treatments for Parkinson's act in the same way and aim to re-establish the faulty transmission between neurons. Unfortunately, they have no effect on the cause or progression of the disease.
Deep brain stimulation is also a frequent therapy used to treat the symptoms of the disease.
Other non-medicinal approaches such as regular physical activity and intellectual activities are beneficial for Parkinson's disease disorders.
