Parkinson’s disease (PD) and related conditions are chronic, progressive disorders that occur when certain nerve cells in the brain die or become impaired. Normally, these cells produce a chemical called dopamine, which allows coordinated function of muscles and movement. When most of the dopamine-producing cells are damaged, the motor symptoms of Parkinson’s disease appear.
According to the National Parkinson Foundation, researchers suspect that PD is caused in most people by a combination of genetic factors, exposure to environmental toxins, viral infections, repeated head injuries and advanced age. An estimated 1.5 million people in the United States have PD, and it affects about one in 100 Americans over age 60.
Parkinson's Disease Symptoms
The four major symptoms of Parkinson’s disease are:
- Resting tremor (trembling in hands, arms, legs, jaw and face), which occurs in about 70 percent of people with PD
- Rigidity or stiffness of the limbs and trunk
- Bradykinesia (slowness of movement)
- Impaired balance/posture and coordination
As symptoms progress, patients may have difficulty walking, talking or doing simple tasks. A diagnosis is based on a medical history and a physical exam with a movement disorders physician specialist. Usually, two of the four major symptoms must be present to consider a diagnosis of PD.
About 15 percent of patients originally diagnosed with PD begin to show signs of having “atypical” parkinsonism, also called “Parkinson-plus” syndrome. Parkinsonism refers to conditions that mimic PD, with symptoms such as tremor, slow movements, stiff muscles and balance and walking difficulties. These symptoms, however, are caused by another condition. Various conditions can cause parkinsonism or Parkinson-plus syndromes, and diagnosis can be complex.
Other Forms of Parkinsonism
Progressive Supranuclear Palsy
Progressive supranuclear palsy (PSP) is a rare brain disorder that causes serious and permanent problems with walking and balance control. Symptoms include difficulty aiming the eyes, and mood and behavior changes. PSP begins slowly and progresses, causing weakness (palsy) by damaging certain parts of the brain.
Multiple System Atrophy
Multiple system atrophy (MSA) is a rare, progressive neurodegenerative disorder with symptoms that affect movement, blood pressure and other body functions. MSA affects people primarily in their 50s.
There are three subtypes of multiple system atrophy:
- Parkinsonian-predominant (striatonigral degeneration), caused by a disruption in the connection between two areas of the brain — the striatum and the substantia nigra.
- Autonomic-predominant with parkinsonian features (Shy-Drager syndrome), a progressive disorder of the central nervous system and the autonomic nervous system, which regulates certain body functions.
- Cerebellar parkinsonism (olivopontocerebellar atrophy), a mixture of parkinsonian and cerebellar features.
Corticobasal degeneration (CBD) involves nerve cell loss and atrophy (shrinkage) of many areas of the brain including the cerebral cortex and the basal ganglia. The disease progresses gradually. Symptoms usually begin around age 60 and may first appear on one side of the body, affecting both sides as the disease progresses.
Diffuse Lewy Body Disease
Diffuse Lewy body disease (DLBD) is a spectrum of diseases involving dementia and motor symptoms, and the second most common cause of dementia. Because the dementia is similar to that of Alzheimer’s, and other symptoms imitate Parkinson’s disease, the disease can be difficult to diagnose. However, patients with DLBD have hallucinations and are very sensitive to antipsychotic medications. DLBD is more common in men than women.
Vascular parkinsonism is a neurological disorder in which the symptoms are a result of small strokes rather than a loss of nerve cells. When one or more strokes occur in the basal ganglia (the part of the brain that controls movements) on one side of the brain, a person may develop parkinsonism on the opposite side of the body.