What is Parkinson’s Disease?
Parkinson’s disease (PD) is a movement disorder of the nervous system that gets worse over time. As nerve cells (neurons) in parts of the brain weaken, are damaged, or die, people may notice problems with movement, tremors, stiffness in the limbs or the trunk of the body, or impaired balance. As symptoms progress, people may have difficulty walking, talking, or completing other simple tasks. Not everyone with one or more of these symptoms has PD, as the symptoms appear in other diseases as well.
There is no cure for PD, but research is ongoing, and medications or surgery can often provide substantial improvement in motor symptoms.
The four primary symptoms of PD are:
- Tremor—Tremor (shaking) often begins in a hand, although sometimes a foot or the jaw is affected first. The tremor associated with PD has a characteristic rhythmic back-and-forth motion that may involve the thumb and forefinger and appear as a “pill-rolling.” It is most obvious when the hand is at rest or when a person is under stress. This tremor usually disappears during sleep or improves with a purposeful, intended movement.
- Rigidity—Rigidity (muscle stiffness), or resistance to movement, affects most people with PD. The muscles remain constantly tense and contracted so that the person aches or feels stiff. The rigidity becomes obvious when another person tries to move the individual’s arm, which will move only in short, jerky movements known as “cogwheel” rigidity.
- Bradykinesia—This is a slowing down of spontaneous and automatic movement that can be particularly frustrating because it may make simple tasks difficult. Activities once performed quickly and easily—such as washing or dressing—may take much longer. There is often a decrease in facial expressions (also known as “masked face”).
- Postural instability—Impaired balance and changes in posture can increase the risk of falls.
PD does not affect everyone the same way. The rate of progression and the symptoms differ among individuals. PD symptoms typically begin on one side of the body. However, the disease eventually affects both sides, although symptoms are often less severe on one side than on the other.
People with PD often develop a so-called parkinsonian gait that includes a tendency to lean forward, taking small quick steps as if hurrying (called festination), and reduced swinging in one or both arms. They may have trouble initiating movement (start hesitation), and they may stop suddenly as they walk (freezing).
Who is more likely to get Parkinson’s disease?
Risk factors for PD include:
- Age—The average age of onset is about 70 years, and the incidence rises significantly with older age. However, a small percentage of people with PD have an “early-onset” disease that begins before the age of 50.
- Biological sex—PD affects more men than women.
- Heredity—People with one or more close relatives who have PD have an increased risk of developing the disease themselves. An estimated 15 to 25 percent of people with PD have a known relative with the disease. Some cases of the disease can be traced to specific genetic mutations.
- Exposure to pesticides—Studies show an increased risk of PD in people who live in rural areas with increased pesticide use.
The precise cause of PD is unknown, although some cases are hereditary and can be traced to specific genetic mutations. Most cases are sporadic—that is, the disease does not typically run in families. It is thought that PD likely results from a combination of genetics and exposure to one or more unknown environmental factors that trigger the disease.
Parkinson’s disease occurs when nerve cells, or neurons, in the brain die or become impaired. Although many brain areas are affected, the most common symptoms result from the loss of neurons in an area near the base of the brain called the substantia nigra. The neurons in this area produce dopamine. Dopamine is the chemical messenger responsible for transmitting signals between the substantia nigra and the next “relay station” of the brain, the corpus striatum, to produce smooth, purposeful movement. Loss of dopamine results in impaired movement.
Studies have shown that most people with Parkinson’s have lost 60 to 80 percent or more of the dopamine-producing cells in the substantia nigra by the time symptoms appear. People with PD also lose the nerve endings that produce the neurotransmitter norepinephrine—the main chemical messenger to the part of the nervous system that controls many automatic functions of the body, such as pulse and blood pressure. The loss of norepinephrine might explain several of the non-motor features seen in PD, including fatigue and abnormalities in blood pressure regulation.
The protein alpha-synuclein—The affected brain cells of people with PD contain Lewy bodies—deposits of the protein alpha-synuclein. Researchers do not yet know why Lewy bodies form or what role they play in the disease. Some research suggests that the cell’s protein disposal system may fail in people with PD, causing proteins to build up to harmful levels and trigger cell death. Additional studies have found evidence that clumps of protein that develop inside the brain cells of people with PD may contribute to the death of neurons.
Genetics—Several genetic mutations are associated with PD, including the alpha-synuclein gene, and many more genes have been tentatively linked to the disorder. The same genes and proteins that are altered in inherited cases may also be altered in sporadic cases by environmental toxins or other factors.
Environment—Exposure to certain toxins has caused parkinsonian symptoms in rare circumstances (such as exposure to MPTP, an illicit drug, or in miners exposed to the metal manganese). Other still-unidentified environmental factors may also cause PD in genetically susceptible individuals.
Mitochondria—Mitochondria are the energy-producing components of the cell and abnormalities in the mitochondria are major sources of free radicals—molecules that damage membranes, proteins, DNA, and other parts of the cell. This damage is often referred to as oxidative stress. Oxidative stress-related changes, including free radical damage to DNA, proteins, and fats, have been detected in the brains of individuals with PD. Some mutations that affect mitochondrial function have been identified as causes of PD.
Article provided by the National Institute of Neurological Disorders and Strokes.
The Excelsior Springs Hospital Rehabilitation Department offers LSVT BIG & LOUD therapy. It is a scientifically documented efficacious program for treating voice and speech disorders in patients with Parkinson’s disease. LSVT BIG is the intensive, amplitude-focused physical and occupational therapy component.
For more information on LSVT BIG & LOUD, visit your primary care physician and ask for a referral to our program.