Parkinson's disease is a slow, but progressive neurodegenerative disorder, primarily affecting the control of movements and balance.
It is the most common of a group of diseases known as "Movement Disorders."
The first partial descriptions of the symptoms of Parkinson's disease date back to thousands of years ago ; in fact, they are already mentioned in ancient Chinese (Su Wen), Indian (Ayurveda), Greek (Iliad) and Roman texts among others, as well as in the Old Testament (Ecclesiastes) and the Gospel (Luke).
Many famous personalities, well known for their studies in Medicine, ranging from Hippocrates and Galen to Leonardo Da Vinci, have described these symptoms throughout human history; references to Parkinson's disease are also found in art (for example, the famous innkeeper portrayed in Rembrandt's painting "The Good Samaritan") and literature (Shakespeare's history play “Henry VI”).
However, the first systematic and detailed description of Parkinson's disease is attributed to James Parkinson (after whom the disease is named), a 19th century apothecary and surgeon from London; he had the insight to understand that the symptoms reported by 6 different patients could be ascribed to a previously unknown disease, by publishing his findings in the now famous book, "An Essay on the Shaking Palsy."
Parkinson's Disease is the second most common neurodegenerative disease in the world and is typical of old age.
The prevalence of this disease is slightly higher in males than in females.
Although a number of specific genes (PARK1, PARK2, etc.) and particular substances (trichlorethylene, heavy metals, etc.) have been recognized as associated with development of the disease, the most convincing etiological hypothesis to date is the multifactorial one, i.e., all risk factors are involved in a more or less "weighted" manner in Parkinson’s disease development.
Whatever the initial event leading to Parkinson's disease may be, the first manifestations occur after the loss of more than 60% of neurons in a specific area of the brainstem, called Substantia Nigra, which produces an important neurotransmitter, dopamine, that is essential for the "control and transmission of messages" along the motor pathways.
This fine circuit, which regulates voluntary muscles, links together different brain areas located both in the deep regions of the brain, such as the basal ganglia (caudate nucleus, putamen and globus pallidus), and in the superficial regions of the brain, such as the primary motor cortex, the supplementary motor area and the premotor cortex.
Since there are no specific diagnostic tests, Parkinson’s disease diagnosis is essentially clinical and is based on the presence of characteristic signs and symptoms, the most common of which are tremors, rigidity, slow movements, balance and gait disorders. The diagnosis is usually made by a specialist neurologist, who can also make use of instrumental tests such as brain MRI, or functional neuroimaging techniques (e.g., PET, SPECT, fMRI, 123I-MIBG myocardial scintigraphy) to refine the diagnosis and distinguish it from other similar disorders (parkinsonisms).
Parkinson's disease has a great impact on the quality of life of patients as it affects, with various degrees of severity, motor, vegetative, behavioral and cognitive functions. The latter are often directly related to the
disease (i.e., depression and sleep disorders) or side effects of certain medications (e.g., hallucination, confusion state).
The main pharmacological approaches include levodopa, or L-dopa, (associated with a dopa decarboxylase inhibitor), dopamine agonists (DAs), catechol-O-methyl transferase (COMT) inhibitors, and monoamine-oxidase-B (MAO-B) inhibitors; these agents , administered alone or in combination, depending on the degree of severity of the disease, are able to improve symptoms and consequently the quality of life as well as to slow the progression of the disease.