By James Coggin, M.D.
Every movement of the body requires communication among the central nervous system—especially the brain and spinal cord—and the nerves and muscles. Movement occurs when specialized clusters of neurons in and around the brain stem, called basal ganglia, release neurotransmitters, chiefly dopamine. When there is insufficient formation and action of this neurotransmitter, degenerative disorders can occur, impairing one’s motor skills, speech, and many non-motor skills as well.
Parkinson’s disease (PD) is a chronic, progressive, and degenerative neurological disorder characterized by a loss of dopamine-producing neurons in the substantia nigra (Latin for “black substance”), a small region in the brain stem. The brain stem connects the spinal cord to the brain and is comprised of the medulla oblongata (myelencephalon), pons (metencephalon), and mid-brain (mesencephalon). Parkinson’s disease or “primary parkinsonism,” results from a neurodegenerative process without any secondary systemic cause. Patients typically experience muscle rigidity, tremors, bradykinesia (slowing of movement), and ataxia (poor balance).
The symptoms of Parkinson’s disease, as well as possible therapies, were discussed in the Ayurveda, the system of medicine that has been practiced in India since 5000 BC, and Nei Jing, the first Chinese medical textbook, published 2,500 years ago. Descriptions of symptoms and treatment of PD date back to medieval times, most notably by Averroes.
Researchers estimate that between 500,000 and one million Americans have Parkinson’s disease, making it one of the most common neurodegenerative disorders in the U.S., second only to Alzheimer’s disease. These statistics are not precise, however, because Parkinson’s is frequently misdiagnosed. The disease occurs in one of two forms: idiopathic (or sporadic) or — rarely — familial. Most forms of PD are idiopathic while secondary cases can result from drugs, head trauma, and other medical disorders. Some forms have a genetic or familial basis.
A number of environmental factors has been linked to an increased incidence of Parkinson’s disease. These include:
- exposure to heavy metals and pesticides.
- living in a rural area within an industrialized country.
- exposure to jet fuel.
- drinking well water.
- not smoking cigarettes.
The elderly are particularly affected. Parkinson’s is the second-most common neurodegenerative disease of the elderly, and about one percent of Americans over age 65 has been diagnosed with PD. While the average age of onset is about 60 years, the disorder does occur in younger people. In fact, five to 10 percent of cases are diagnosed before age 40. People with early-onset Parkinson’s discover initial symptoms between the ages of 21 and 40. The first symptom in juvenile-onset disease occurs before the age of 20.
People of all ethnic origins can develop Parkinson’s disease although it is slightly more prevalent in Caucasians than in Asians or African-Americans in the United States.
Parkinson’s occurs with slightly greater frequency in men than in women. About 15 percent of sufferers have a first-degree relative who also has the disease although there is typically no clear path of inheritance. Researchers suggest that most cases arise from a combination of factors, including genetic susceptibility, exposure to certain toxins, and aging.
You can learn more about Parkinson’s disease by reading our Parkinson’s Disease & ALS