Parkinson’s disease is a progressive neurological disorder that affects approximately 1.5 million individuals in the United States. Typically, people start showing symptoms over the age of 50. In fact, aging is the only known risk factor for the development of this disorder.
Parkinson’s disease is characterized by slowness of movement, muscular rigidity, and walking and balance impairment. Many affected individuals may develop a resting tremor as well. Besides impairment in motor movement, Parkinson’s may also cause changes in non-motor brain function.
On a cellular level, Parkinson’s disease is the result of the loss of dopamine-producing cells in the region of the brain called the substantia nigra pars compacta, found in the midbrain. A large number, 40 percent, of cells must be lost before symptoms occur, suggesting that perhaps the brain has a way of warding off symptoms. Eventually, however, these mechanisms begin to fail, or the continued loss of cells leads to a threshold from which the brain can no longer recover.
Although the cause of Parkinson’s remains unknown, most researchers believe that there are both genetic and environmental factors that contribute to the injury and eventual loss of these dopamine-producing cells. While most cases of Parkinson’s do not appear to be inherited, there are certain situations in which genetic factors may be involved. For example, studies indicate that cases of early onset Parkinson’s may be inherited. Research on various forms of the disease may help provide clues about it, as well as insights into potential new treatments.