Parkinson’s disease (PD), also known historically as paralysis agitans or shaking palsy, results from a disorder of the neurons in the brain that are responsible for production of the neurotransmitter dopamine. Dopamine is a signaling molecule to other neurons that manage the coordination of body movement. When these cells die or fail to work properly, the symptoms of PD begin to appear, often very gradually.
Most cases occur, apparently randomly, in about 1% to 2% of people more than 60 years old, and they occur twice as often in men as in women. Diagnosis of PD is based on medical history and neurologic examination because there are as yet no confirming blood or other markers. This may eventually change with more advances in understanding the role of genetics and with ongoing improvements in brain imaging techniques (Medline Plus, 2012).
PD is characterized clinically by tremor in the hands, arms, legs and jaw; muscle rigidity in the limbs and body; impaired balance, coordination, and stability; and bradykinesia (slowed movement). These impairments can lead to fatigue and sleep problems, writing and speech difficulties, and a characteristic stooped posture; they will eventually lead to difficulty with or loss of walking, communication, chewing and swallowing, and other activities of daily life (ADLs). The progression of symptoms can be unpredictable and somewhat different for each patient. Many symptoms can be ameliorated, sometimes near the point of vanishing, with various medications or other therapies, though none of the known therapies appear to be permanent solutions.
Many patients also have depression, irritability, and visual hallucinations, with eventual dementia developing in 20% of cases. There is some evidence for an increased risk of PD in people exposed to certain pesticides and a reduced risk in tobacco smokers, who may be protected by nicotine (see later discussion). The combined direct and indirect cost of Parkinson’s disease is estimated to be $28 billion per year in the United States, and medication costs for an individual person with PD average $2500 a year. Therapeutic brain surgery can cost up to $100,000 per patient (NINDS, 2012).
About 65,000 Americans are diagnosed with Parkinson’s disease each year, and there are now estimated to be 1.5 million Americans living with PD. These numbers are expected to increase as the population continues to age. Based on the age of onset of symptoms, PD has several classifications. Individuals with symptoms that start before the age of 20 years are said to have juvenile onset PD, those with adult onset before 50 years of age have early onset PD, and those whose symptoms start after age 50 have late onset PD. Only about 4% of all PD cases are juvenile or early onset PD. Diagnosis of typical cases is based on accumulating symptoms, with neuro-imaging or other tests used for confirmation of suspected disease, and to rule out other causes. Unfortunately there is still no cure for PD, though promising therapies are being actively researched and developed.
Public awareness campaigns make use of a red tulip as the symbol of the disease and include an annual Parkinson’s disease day, April 11, the birthday of physician James Parkinson. Well-known people with Parkinson’s disease include the actor Michael J. Fox and former boxer Muhammad Ali (Wikipedia, 2012a).