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Study Indication: Idiopathic Parkinson's Disease
Idiopathic Parkinson's disease is the most common form of parkinsonism, a group of movement disorders with similar features and symptoms. Parkinson's disease is called idiopathic Parkinson's because the cause is unknown. In the other forms of parkinsonism, a cause is known or suspected.
Parkinson's disease is the second most common neurodegenerative disorder that afflicts 1 to 1½ million people in the United States, with annual direct medical costs approaching $6 billion. While all races can be affected, Parkinson's disease tends to be more prevalent among Caucasians. Men are affected slightly more often than women.
Although symptoms of Parkinson's disease may occur at any age, the average age of onset is 60 years. The risk of developing Parkinson's disease increases with age and rarely appears in people younger than 30 years. About 5% to 10% of Parkinson's disease patients experience symptoms before the age of 40.
Etiology
Parkinson's disease is a chronic, progressive neurodegenerative movement disorder that results from a complex series of cortical and subcortical changes and disruptions. Initially, it was believed that Parkinson's disease resulted primarily from the degeneration of dopamine-producing nerve cells in the substantia nigra. Dopamine is a neurotransmitter that stimulates motor neurons, the nerve cells that control the muscles. When dopamine production is depleted, the motor system nerves are unable to effectively control movement and coordination. Parkinson's disease patients have typically lost 80% or more of their dopamine-producing cells by the time symptoms appear.
It is now known that this is only one part of the degenerative process that manifests itself as Parkinson's disease. Neuronal degeneration in Parkinson's disease patients has also been documented in the locus ceruleus, raphe nuclei, basal forebrain cholingeric neurons and dorsal motor nucleus of the vagus. Senile plagues, similar to those occurring in Alzheimer’s disease, have also been found in Parkinson's disease patients in the amygdala, hippocampus and neocortex, in particular where depression symptoms are manifested in a patient. Cerebral glucose metabolism is reduced throughout the brain. The DA neurons of the meso-cortico limbic circuit, which originate in the ventral tegmental area and medial substantia nigra, project to phylogenetically older or “limbic” regions including olfactory bulb, piriform cortex, amygdaloidal nuclei and septal nuclei as well as nucleus accumbens and neocortical areas, especially frontal and anterior cingulated cortices. Physiologic and pharmacologic evidence suggests that this system is important for motor, mental, and cognitive functions with degeneration of these projections contributing to development of diverse features including akinesia, freezing and mental depression. In Parkinson's disease patients, damage to the mesocortical DA projections has been associated with frontal lobe dysfunction. |