Parkinson’s disease and Tremors

What is Parkinson’s Disease?

More than one million people in the United States are doing battle with the neurodegenerative ravages of Parkinson’s disease. This disease, which typically hits people past the age of 65, gradually strips away motor abilities, leaving them with a slow and awkward gait, rigid limbs, tremor, shuffling and a lack of balance. Patients can lose facial expression and sometimes the ability to speak. In as many as half, the disease also comes with psychiatric complications of anxiety and depression.

No one knows what causes Parkinson’s. Most cases arise spontaneously; some are hereditary. What is known is that brain cells in the area of the brain called the “substantia nigra” die off. These are the cells which manufacture the molecule dopamine, a chemical that helps control muscle movement. Drug therapies have focused on replacing the dwindling supply of dopamine or addressing specific symptoms associated with the disease. Thanks to recent advances in the lab, including the pinpointing of several Parkinson’s genes, research is exploding. Scientists are now picking apart newly discovered biochemical pathways involved in the disease and uncovering new targets for therapy.

What causes Parkinson’s disease (PD)?

Parkinson’s disease is a progressive neurological disease involving loss of neurons in a part of the brain called the substantia nigra. This results in a reduction in the amount of the chemical dopamine, a chemical messenger or neurotransmitter. When 80 percent of dopamine in the brain is depleted, the symptoms of Parkinson’s disease develop. The main symptoms are tremor, slowness of movement, stiffness and impairment of balance. It is a highly treatable disease and the life span is not shortened.

The loss of dopamine in an area of the brain called the striatum is the main chemical abnormality and there is a correlation between dopamine loss in this area of the brain and the severity of the symptoms. It is thought that exposure to some unidentified environmental toxin in a person who has a certain genetic predisposition causes the person to develop the disease. Inside the dopamine neurons, there are structures called mitochondria which use oxygen to turn food into energy. These mitochondria may be damaged in people with Parkinson’s disease.

Who gets Parkinson’s?

Parkinson’s Disease affects less than one percent of the general population, but three percent or more of those are older than 60. There are approximately 60,000 people diagnosed with the disease per year. The average age of onset of symptoms is 60, but five to ten percent of patients have symptoms before the age of 40. The prevalence is expected to triple in the next 50 years.

How is Parkinson’s diagnosed?

Persons are diagnosed based on the symptoms they have and the physical examination. There are no standard laboratory tests available although testing is often done to exclude other similar diseases. A significant improvement in symptoms related to taking the medication carbidopa/levodopa is helpful in making the diagnosis since all patients with Parkinson’s Disease respond to this medication.

What are the primary symptoms of Parkinson’s?

Typically, as the disease progresses, persons with Parkinson’s disease will also suffer from impairment of the autonomic nervous system, develop difficulty with sleep and speech, and sustain physical injuries due to falls. Frequently, psychiatric problems will develop as well, particularly depression and cognitive impairment.

The following are the most common symptoms of Parkinson’s disease. However, each individual may experience symptoms differently. Symptoms may include:

  • muscle rigidity – stiffness when the arm, leg, or neck is moved back and forth.
  • resting tremor – tremor (involuntary movement from contracting muscles) that is most prominent at rest.
  • bradykinesia – slowness in initiating movement.
  • postural instability – poor posture and balance that may cause falls; gait or balance problems.

Muscle Rigidity:
Rigidity is felt as a stiffness or tightness in the arms, legs, neck or trunk. It is not uncommon for a patient to be evaluated and treated for arthritis in a shoulder prior to diagnosis of Parkinson’s disease. This symptom responds well to anti-Parkinson’s medications.

Resting Tremors:
The tremor in Parkinson’s disease is a characteristic one in that it occurs at rest rather than when the limb is being used and it is fairly slow occurring at a rate of about five times per second. It usually begins in one arm, but spreads to involve the other side, sometimes the legs and occasionally the jaw. The tremor is usually reduced or eliminated when the limb is being used in some purposeful way. For this reason, the tremor is often not functionally limiting. This symptom responds fairly well to anti-Parkinson’s medications. For some patients, however, medications are not effective in treating the tremors. In these individuals, deep brain stimulators implanted in the thalamus can achieve very satisfactory results.

Bradykinesia (Slowness of Movement):
Slowness of movement may be very disabling and is one of the major symptoms for which treatment is sought. It may impair ability to perform tasks involving the arms such as writing and buttoning, and the legs as when walking. The handwriting is characteristically small (micrographia) and this may be one of the first signs noted by some patients. This symptom responds well to anti-Parkinson’s medications.

Postural Instability (Walking and Balance Difficulties):
One of the first signs of Parkinson’s disease is often a decrease in the natural swing of one of the arms when walking. As the disease progresses, this involves both sides and there may be a difficulty in taking large steps so that a shuffling gait develops. There may be a tendency to take rapid short steps and to even have trouble stopping. With advancing disease, there may be “freezing” episodes where the feet feel as if they are glued to the floor and taking any steps at all becomes very difficult. Also with advancing disease, there may be impairment of balance. This may be related to a diminished ability to make corrective adjustments in the posture to prevent falling. When these later symptoms develop, physical therapy and the use of assistive devices such as canes and walkers, is recommended. Unfortunately, the balance problems do not respond well to anti-Parkinson’s medications.

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