Parkinson’s disease (PD) is one of the most prevailing neurodegenerative
disorders affecting populations all over the world. Almost from 4.1 to 4.6 million patients
suffering from PD are counted across the
fifteen most crowded countries where
live the two thirds of the world population. The average age of the PD
onset is 55. The incidence grows along with the age: from 20/100000 cases in
the overall population to 120/100000 in the elder population above 70 years
old.
Gender difference in the rate of
incidence of PD was reported in many epidemiological studies: from 1.5 to 2 times higher in men than in women.
In Japan, however, there is a higher incidence in women.
Environmental factors
are critical in determining the incidence rate of the disease. Some studies
report that, among the cases in which Parkinson's disease is attributable to
factors of environmental exposure, 10% is associated with the use of herbicides
in the professional field. US epidemiological studies show a significant
association between mortality rates for parkinsonian years 1986-1988 and the
presence of the chemical in the territory. Only in 5% of cases
ensures inheritance of the disease.
It
is a disease that involves functions such as control of movements and balance. But what exactly is happening in the brain? The substantia nigra is a structure of Basal Ganglia [see here the basal ganglia circuit] that is rich of dopaminergic neurons. In Parkinson these neurons get sick and die, and when the cell loss reachs 80% the symptoms of the disease appear:
tremor, slowness of movement and rigidity.
The main
pharmacological therapy involves the administration of a drug, levodopa, which
is converted to dopamine in the brain. By increasing the concentration of this
substance symptoms diminish, slow movements and tremors disappear.
For
the first five to six years the patient returns to a normal condition and a
good quality of life. Then, however, begin new problems. The major complications
related to the assumption of levodopa or dopamine agonists include dyskinesias such as fluctuations
of the movement, involuntary movements very fast like tics affecting the face,
mouth, tongue, upper limbs and sometimes even lower. These are side effects of the drug that interfere so
heavy with normal daily activities.
An italian research team has investigated what happens in the brain in patients
suffering from severe dyskinesia. The studies began a few years ago and were conducted over hundreds of
patients.
The main findings showed that to be involved is the right inferior frontal gyrus,
which modulates voluntary movements. In case of prolonged intake of levodopa anatomic and functional alterations were observed and this would cause the onset of motor disorders.
The researchers applied repetitive transcranic magnetic stimulation (R-TMS) to PD patients. The stimulation of the
See more on this research here
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