Parkinson's disease (PD) is a slowly progressive neurological disorder with primary symptoms of resting tremor, slowness, stiffness, and problems with balance. Parkinson's disease (PD) occurs equally often in men and women, and occurs with similar frequency in all ethnic groups.The disease is usually diagnosed in people between the ages of 45 and 65.
There are two types of PD: idiopathic and secondary. The major type of Parkinson's disease is called idiopathic Parkinson's, and has no known cause. Approximately 25% of PD cases come from secondary causes such as head trauma, exposure to toxins, brain infection, and certain drugs. This article focuses on idiopathic PD.
PD results when dopamine is lost in the portion of the brain that helps to coordinate movement (the basal ganglia) Figure 01. When nerve cells degenerate within a structure of the brain that connects to the basal ganglia (called the substantia nigra), levels of a brain chemical called dopamine decrease. This decrease impairs communication between nerve cells in the brain, and causes the symptoms of PD.
Researchers still don't know why nerve cells degenerate. However, they believe that it may occur as a result of interactions between environmental and genetic factors. Some researchers believe that exposure to toxins might contribute to PD; manganese dust and carbon disulfide are two such toxins that have been linked to the disease. In addition, a substance linked to heroin use called MPTP has also been associated with PD.
While several genetic factors are thought to be linked to Parkinson's disease, it is rare that Parkinson's runs in families.
It is thought that cells in the brain are destroyed by substances called free radicals. Free radicals are produced by chemical processes in the brain. Medications called antioxidants are used to control free radicals.
Secondary PD can result from other diseases, infection, toxins, head injuries, and certain drugs that affect the brain chemical dopamine.
Figure 01. Basal Ganglia and Corpus Striatum
PD symptoms appear gradually and slowly get worse Table 01. Often, the first symptom is a hand tremor that occurs while resting. The tremor lessens when you move your hand, and usually disappears during sleep. This may be the only symptom you have for months or even years.
The tremor is slow and rhythmic, and can get worse with stress and fatigue. It often is described as a “pill-rolling” motion of the thumb and forefinger. In most cases, the tremor will eventually spread to the other hand and the arms and legs, as well as to the mouth and chin.
Table 1. Symptoms of Parkinson's Disease
Tremor when at rest Sluggish initiation of movements Slow movements Muscle stiffness
If you have PD, you will have stiff muscles and slow movements. These symptoms can make it difficult for you to perform many activities. For example, sitting down in a chair and getting up from a sitting position will become difficult. Your handwriting may become illegible, and it may become difficult for you to wash and dress yourself.
People with PD walk with a shuffle and a posture that gradually tilts forward. If you have PD, you may have a short-stepped rapid gait that propels you forward and increases your risk of falling. You may also have difficulty turning and stopping while walking.
PD causes loss of facial animation, which leads to an expressionless look. If you have PD you may have widely opened eyes, and may blink more slowly than normal. You may also have slowed swallowing and soft, monotonous speech.
Your risk for Parkinson's disease increases with age. While only 1 or 2 of every 1,000 people in the general population have PD, 1 in 100 people older than 50 and 2.5 in 100 over the age of seventy have the condition.
When making a diagnosis, your doctor will ask you about symptoms, and will perform a neurological exam. The diagnosis of PD can be difficult because in the beginning the symptoms are very subtle. An arm that doesn't swing or leg that drags can often be mistaken for arthritis or a pinched nerve. Tests may be done to rule out other diagnoses, but a diagnosis of PD is made purely on a history and physical exam.
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