Parkinson's disease

Parkinson's disease is a neurological disorder that causes progressive loss of muscle control and movement disorders.

Parkinson's disease involves the loss of motor function because cells in the brain fail to produce enough of the neurotransmitter dopamine. This loss of dopamine leads to decreases in the ability to control muscle movement along with muscle stiffness. Although symptoms may develop rapidly, in many people symptoms come on slowly and do not tend to shorten life expectancy, although they do create disability.

Individuals with early Parkinson's disease have tremors or shakiness in their arms, fingers, hands, legs, feet, or jaw. These tremors usually occur when the individual is at rest and disappear when the person is engaged in movement. Other common symptoms are rigidity or stiffness in the limbs, slow voluntary movements (bradykinesia), and poor balance and coordination.

Risk factors for developing Parkinson's disease include:

Parkinson's disease is the second most common neurodegenerative disorder in the United States and the first most common movement disorder. It affects about 1% of people over age 60 years with a prevalence of about 120 cases per 100,000. The disease is uncommon in people under age 40. About 1.5 times more men than women develop Parkinson's disease. Complications from Parkinson's disease are the fourteenth leading cause of death in the United States.

The symptoms of Parkinson's disease are caused by the gradual breakdown of neurons (nerve cells) in the brain that produce the chemical dopamine. Dopamine helps to regulate movement and emotion. As these neurons break down, their failure to produce adequate dopamine causes tremor, slow movements, and muscle rigidity. It is not clear why these cells break down. Exposure to environmental toxins is thought to be a factor. A genetic cause can be identified only in about 10% of cases.

During autopsy, researchers have found that the brains of people with Parkinson's disease contain Lewy bodies. Lewy bodies are clumps of abnormal proteins that develop inside nerve cells. Lewy bodies contain a protein called alpha-synuclein that nerve cells cannot break down. Researchers do not know what causes Lewy bodies, but they believe Lewy bodies are related to the development of Parkinson's disease and some forms of dementia.

Parkinson's disease is a progressive disorder. Symptoms worsen over time. Movement symptoms include:

Symptoms not related to movement include:

Various ways of staging the progression of Parkinson's disease have been proposed. There is no complete agreement on how to define the stages. The Parkinson's Foundation uses the following staging definitions.

There are no laboratory tests or specific biomarkers that identify a person has having Parkinson's disease. Magnetic resonance imaging and computer tomography scans are within the normal range. The disorder is diagnosed by the presence of at least two of the following symptoms: tremor while at rest, muscle rigidity, slowness of muscle movement. Tests may be done to rule out other diseases that share some symptoms of Parkinson's disease.

As of 2018, there was no cure for Parkinson's disease. Treatment is aimed at controlling symptoms and delaying worsening of symptoms.

Drug treatment attempts to control symptoms with the least unacceptable side effects. Common drugs used are levodopa or a combination of levodopa/carbidopa (Sinemet, Rytary). Catechol-O-methyltransferase (COMT) inhibitors such as entacapone (Comtan) help prolong the effects of levodopa. Levodopa often controls early symptoms, but long-term use causes unacceptable side effects, including increasingly erratic movements.

The monoamine oxidase B inhibitors (MAO-B) selegiline (Eldepryl, Zelapar) and rasagiline (Azilect) are also used to help control symptoms but also have undesirable side effects.

Dopamine agonists are drugs that mimic the effects of dopamine in the brain. They include pramipexole (Mirapex), ropinirole (Requip) and rotigotine patch (Neupro). Other drugs may be prescribed to treat specific symptoms, non-motor symptoms, or because of intolerable side effects caused by preferred drugs.

Deep brain stimulation involves implanting an electrode in the brain that is controlled by a generator implanted near the collarbone that sends electrical impulses to the electrode. The surgery does not destroy any brain tissue and is reversible. It may be used in individuals with advanced Parkinson's disease who have unstable responses to medication. Although it offers benefits, deep brain stimulation does not prevent symptoms from worsening.

Exercise and physical therapy may be helpful in preserving gait, balance, and flexibility. Occupational therapy may be helpful in creating strategies to cope with activities of daily living. Occupational therapists can also help individuals and caregivers design safer living spaces to help prevent falls.

There are no alternative treatments that can cure or reverse Parkinson's disease; however, some individuals find the following complementary treatments helpful in reducing stress, improving flexibility, and maintaining posture.

Since it is unclear what causes Parkinson's disease, prevention is not possible. However, avoiding exposure to pesticides, herbicides, insecticides, and solvents is prudent as these are considered likely environmental triggers for Parkinson's disease.

See also Neurotoxin ; Smoking .