About Parkinson’s Disease
Parkinson's disease (PD) is a progressive, neurodegenerative disorder that primarily affects movement, muscle control, and balance, but can also affect non-motor functions. It is part of a group of conditions known as motor systems disorders. The disease was named for James Parkinson, a general practitioner in London who first described its symptoms in the 19th century.
The underlying disease process of Parkinson's disease involves the death of dopamine-producing cells and the subsequent reduction of available dopamine in the brain which affects motor function. The hallmark symptoms of Parkinson's disease (PD) are asymmetric (one side of the body) tremors at rest, rigidity (muscle stiffness), bradykinesia (slowness in movement), and impairment of gait and posture (walking and standing erect). There is currently no cure for Parkinson's disease; it is always chronic and progressive, meaning that the symptoms are persistant and typically worsen over time. The rate of progression varies from person to person, as do the intensity of the symptoms. Parkinson's disease itself is not usually fatal and many people live with the disease live into their older years. Mortality in individuals with PD is usually attributable to secondary complications, such as pneumonia or fall-related injuries.
There are three types of Parkinson's disease and they are grouped by age of onset:
Adult-Onset Parkinson's Disease - This is the most common type of Parkinson's disease. The average age of onset is approximately 60 years old. The incidence of Adult-Onset PD rises noticeably as people advance in age (70's and 80's).
Young-Onset Parkinson's Disease - The age of onset is between 21-40 years old. Although the incidence of Young-Onset Parkinson's disease is very high in Japan (approximately 40% of cases diagnosed with Parkinson's disease), it is still relatively uncommon in the U.S., with estimates ranging from 5-10% of all PD cases diagnosed.
Juvenile Parkinson's Disease - The age of onset is before the age of 21. The incidence of Juvenile Parkinson's disease is very low.
According to the American Parkinson's Disease Association (APDA), there are approximately 1.5 million people in the U.S. who suffer from Parkinson's disease - approximately 1-2% of people over the age of 60, and 3-5% of the population over age 85. The incidence of PD ranges from 8.6 to 19 per 100,000 people. Approximately 50,000 new cases are diagnosed in the U.S. annually. That number is expected to rise as the general population in the U.S. ages.
Parkinson's disease occurs when there is a disruption of dopamine production, which leads to impaired neurotransmission (communication between brain cells) in the basal ganglia. As the nerve cells in the brain that make dopamine are destroyed, the reduced levels of dopamine cause the nerve cells to fire out of control, resulting in a loss of smooth, controlled muscle activity. The death of dopamine-producing cells in the substantia nigra leads to reduced levels of dopamine reaching the corpus striatum, which is the primary pathology of Parkinson's disease. By the time symptoms develop, there is at least a 60% loss of dopamine-producing cells in the substantia nigra and an 80 to 90% loss of dopamine in the corpus striatum.
Parkinson's disease is also characterized by the presence of Lewy bodies, - abnormal structures that are found in the nerve cells of the substantia nigra as well as in other secondary locations. Lewy bodies are strongly correlated with neurodegeneration and are considered a diagnostic hallmark of Parkinson's disease.
Early identification of Parkinson's disease (PD) is often missed because the symptoms can be subtle and the progression of disease is typically slow. Individuals may complain of generally not feeling well, feeling a little down, or being just a little shaky. Typically, it is friends or family who first notice that something may be wrong and who encourage an examination by a doctor.
There are four primary motor symptoms of Parkinson's disease, and known as TRAP symptoms, which include:
- Tremor (shaking)
- Rigidity (muscle stiffness)
- Akinesia and Bradykinesia (impaired movement)
- Postural and Gait Instability (impaired balance)
While in the past, Parkinson's disease was considered to be primarily a motor disorder, clinical evidence clearly shows that there is a strong non-motor component to the disease. Nonmotor symptoms of PD contribute significantly to reduced quality of life for PD patients and are the subject of extensive study. Estimates are that up to 80% of people with Parkinson's disease (PD) experience nonmotor symptoms, most of which increase in intensity with progression of the disease. These complications become more and more disruptive in the tasks of daily life and significantly impact quality of life.
Nonmotor symptoms of PD include:
- Psychiatric symptoms
- Cognitive symptoms
- Autonomic nervous system dysfunction
- Sleep disorders
- Sensory abnormalities
As Parkinson's disease progresses, motor symptoms increase, strongly impacting quality of life. Studies report that up to 40% of patients with PD develop motor symptoms within four to six years following disease onset. Motor symptoms may appear as abnormal involuntary movements of the head, trunk, and limbs; motor fluctuations; or an overall decline in motor performance. The development of motor complications has been associated with younger age of onset of PD, increased disease severity, and higher doses of levodopa medication. Motor complications generally increase in severity and frequency with increasing duration of PD.
Currently, there are no blood tests or imaging scans to accurately diagnose Parkinson's disease (PD). The clinical diagnosis of PD is determined by evaluating symptoms and clinical presentation. It is very important that the examining physicians (usually neurologists) have the skill and experience needed to diagnose movement disorders, since Parkinson's disease is misdiagnosed in 25-35% of cases. The incidence of misdiagnosis declines sharply when individuals are evaluated by doctors who specialize in Parkinson's disease and other movement disorders.
Several other conditions can mimic the symptoms of Parkinson's disease and must be excluded before the diagnosis is established. It is important to differentiate between true idiopathic (unknown cause) Parkinson's disease and parkinsonian symptoms that can develop secondary to another underlying condition or as a side-effect of medications.
Treatment for Parkinson's disease is highly individualized. The goal of therapy is to reduce symptoms and improve quality of life while minimizing side effects of medications.
There is currently no cure for Parkinson's disease. With the initial diagnosis of Parkinson's disease, patients and their doctors must determine the level of discomfort or inconvenience of the symptoms in daily life and, based on these findings, establish the initial decisions for therapeutic intervention. There are four basic categories of treatments for Parkinson's disease:
- Lifestyle modifications
- Pharmacological therapy
- Surgical therapy
- Experimental therapies
The Medifocus Guidebook on Parkinson’s Disease is a unique, comprehensive patient education resource that contains vital information about Parkinson’s Disease that you won't find anywhere else in a single resource. The Guidebook will answer many of your questions about this condition that your healthcare provider may not have the time to answer. To learn more about the Guidebook, please click here