Parkinson's disease (PD) is currently recognized as one of the most common neurological conditions. PD is a slowly progressing neurodegenerative disorder that afflicts around 1.5 million people in the U.S. alone, with 50,000 to 60,000 new cases diagnosed each year. Worldwide, it is estimated that approximately five million people have PD.
Symptoms of Parkinson’s Disease
The signs and symptoms of PD can be divided into two distinct categories, motor and non-motor, depending on whether they are related to body movement abnormalities or not.
Motor symptoms, which primarily affect the movements of the body, are the most obvious and well-known clinical features of PD. The chief motor symptoms are slowness of movement (bradykinesia), tremor, muscle stiffness (rigidity), and in later stages of the disease, poor balance (postural instability).
Early on these symptoms are usually mild and confined to one side of the body. However, over the years as the disease progresses, the symptoms worsen, spread to another limb from the same side of the body and eventually to the other side, becoming increasingly impairing. While symptoms usually progress slowly, this can vary from one person to another.
Motor symptoms are usually preceded by non-motor symptoms that include: depression, loss of smell (anosmia), constipation, and vivid dreaming (REM-behavior disorder). However, these individual symptoms are very frequent in the general population, the most likely to precede the motor symptoms is the REM-behavior disorder.
The UC San Diego Department of Neurosciences and movement disorder group are involved in studies searching for markers that could help diagnose PD at earlier stages.
It is now widely recognized that PD is a complex disorder with many non-motor manifestations (including neuropsychiatric) in addition to its better-known motor symptoms. These non-motor symptoms affect the person's mood (e.g., depression), senses (e.g., smell, taste), and ability to think quickly. The most bothersome non-motor symptoms are: cognitive impairment and eventual dementia, depression, fatigue, drop of blood pressure when standing, and urgency to urinate. PD patients also complain of olfactory dysfunction and pain in affected limbs.
Causes of Parkinson's Disease
Although the cause of PD remains unknown, remarkable advances have been made in understanding the possible underlying mechanisms. In normal circumstances, certain brain cells (neurons) are dedicated to the production of dopamine, a chemical important for the communication of neurons within the motor pathways and hence the control of movement.
In people with PD, these neurons, which are located in the area of the brainstem called Substantia Nigra, stop working properly and gradually degenerate and die (neurodegeneration). As a result, dopamine availability decreases and the symptoms progressively develop, becoming more severe over time.
Aggregation (clumps) of a protein that normally exists in the cells, called alpha-synuclein, is found in PD, forming round structures within the cell known as Lewy bodies. The factors and exact mechanisms that lead to the clumps of alpha-synuclein and to the death of the dopaminergic neurons in PD are still not fully understood.
Most movement disorder specialists believe that PD results from a complex interplay between genetic predisposition and environmental factors. When the symptoms present at a younger age (below age 40), Parkinson's disease is often familial (hereditary), caused primarily by genetic mutations of alpha-synuclein or its degradation system.
As familial PD only accounts for a small percentage of cases, the majority of patients have the so-called "sporadic" (no other family members affected) form of the disease. In this case both genetic and environmental risk factors seem to play a decisive role, including genetic predisposition, accumulation of products of oxidative injury (free radicals), exposure to herbicides/pesticides, heavy metals (manganese) and toxins (MPTP) among others.
Diagnosing Parkinson's Diseaese
There are no blood tests or imaging exams that can establish the diagnosis of PD, although they may be helpful in ruling out other possible causes of the symptoms. The diagnosis is clinical and is based on the person's medical history and careful general physical and neurologic examination.
As a rule, two of the three primary motor symptoms (bradykinesia, tremor and rigidity) must be present to make the diagnosis, with one of the symptoms being bradykinesia (extreme slowness of movement). The presence of other associated features helps support the diagnosis, such as when symptoms began on one side of the body or are asymmetric; the tremor occurs at rest; the symptoms improve with PD medications; and suggestive non-motor manifestations.
The signs and symptoms of PD can occur in people with other neurologic conditions, namely the so-called "atypical parkinsonism" or "Parkinson-plus syndromes" (e.g. Progressive Supranuclear Palsy, Multiple System Atrophy, Corticobasal Degeneration, Dementia with Lewy Bodies). These patients experience symptoms that resemble PD — mainly in the early stages of the disease — but in addition have clinical features and a response to treatment that are not typically seen or expected in PD.
Certain medications (e.g. chlorpromazine; haloperidol; metoclopramide; reserpine; valproate) used in many clinical settings may also produce symptoms similar to PD (drug-induced parkinsonism), which is why learning the patient's pharmacologic history is so vital. It is important to distinguish PD from all these other conditions because treatment differs for each of them.
Treatment for Parkinson's Disease
The symptoms of Parkinson's disease can be managed effectively for a significant period of time. Although there is still no cure for PD, there are currently many medical and surgical treatments available for PD and other degenerative diseases of the central nervous system.
The treatment should be individualized, as many factors have to be taken into careful consideration, including the patient's symptoms/signs, age, stage of disease, degree of functional disability, and level of physical activity and productivity. Therefore, the options and decisions may vary significantly from one patient to another.
Considering the ongoing research and clinical trials, as well as the recent advances in the understanding of PD, it is realistic to expect some breakthroughs in PD treatment in coming years.
For a better understanding, treatment can be divided in pharmacologic (drugs), nonpharmacologic, and surgical therapy.
The pharmacologic treatment of PD can be divided into neuroprotective (to stop dopamine-producing nerve cells from dying, preventing the disease) and symptomatic therapy (to ease symptoms of the disease). In reality, nearly all of the available medications are symptomatic in nature and do not appear to reverse the natural course of the disease.
Different types of medications available to treat the symptoms of Parkinson disease include:
- Dopamine agonists
- Inhibitors of enzymes that inactivate dopamine: MAO-B (monoamine oxidase B) inhibitors and COMT (Catechol-O-methyltransferase) inhibitors
PD drug treatment is not limited to the above-mentioned medications (mostly aimed at controlling the motor symptoms), as non-motor manifestations (depression, dementia, psychosis, hallucinations, sleep problems) of PD often require directed drug treatment.
In addition to medications, PD is a chronic disorder that requires a broad-based approach. This includes several nonpharmacologic interventions that are beneficial, namely:
Education: The prospect of having a chronic and progressive neurologic condition can be frightening. Education helps patients and families understand and control the disorder.
Support: The psychological and emotional needs of the patient with PD (and family) should be addressed. Support groups are especially valuable, providing useful educational information and allowing interactions with other patients or families with similar experiences.
In some cases, referral to a psychologist experienced in dealing with chronic illness may be appropriate. Similarly, referral for legal, financial, or occupational counseling might be indicated.
Exercise and Physical Therapy: Regular exercise promotes physical and mental health. Evidence suggests that regular aerobic exercise (brisk walks, tai chi, swimming, and water aerobic exercises) has a beneficial impact on PD, improving balance, flexibility and strength. In addition, many patients gain lasting confidence and sense of control over this aspect of the disease. We can refer patients to a physical therapist.
Speech Therapy: Patients with PD often have speech disturbances and speech therapy can help, especially to improve speech volume and voice quality.
Learn about speech therapy specifically for Parkinson's disease.
Nutrition: In more advanced stages of PD, the patients are at risk for poor nutrition, weight loss, and loss of bone and muscle mass. Some practical guidelines include a high fiber diet and adequate hydration to help manage constipation. Large, high-fat meals that slow gastric emptying and interfere with medication absorption should be avoided.
Deep brain stimulation (DBS) is currently the mainstay surgical procedure for the treatment of advanced PD (and other movement disorders). This technique involves the surgical implantation of two leads into the brain (accurately targeting specific structures within the basal ganglia), which are then connected to a medical device similar to a cardiac pacemaker (neurostimulator) implanted just under the skin in the upper chest area.
Learn more about deep brain stimulation
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Research on Parkinson's Disease
Researchers at UC San Diego are currently looking at Parkinson's disease from multiple angles, from handwriting movements to cognition, to clinical trials to test FDA approved drugs.
Learn more details about current Parkinson's disease research at UC San Diego and how you can get involved