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What is Parkinson's Disease?


Parkinson's disease is a chronic, degenerative neurological disorder that affects one in 100 people over age 60.  While the average age at onset is 60, people have been diagnosed as young as 18.  There is no objective test for PD, so the rate of misdiagnosis can be relatively high, especially when a non-specialist makes the diagnosis. An English doctor, James Parkinson, first characterized Parkinson’s disease extensively in 1817.  


Today, we understand Parkinson's to be a disorder of the central nervous system that results from the loss of cells in various parts of the brain, including a region called the substantia nigra. The substantia nigra cells produce dopamine, a chemical messenger responsible for transmitting signals within the brain that allow for coordination of movement.  Loss of dopamine causes neurons to fire without normal control, leaving patients less able to direct or control their movement.  Parkinson's is one of several diseases categorized by clinicians as movement disorders. (source: The Michael J. Fox Foundation for Parkinson’s Research).  


There are about 1,000,000 Americans diagnosed with Parkinson’s disease, which is more than the combined number of people diagnosed with multiple sclerosis, muscular dystrophy and Lou Gehrig’s disease.  An estimated 7,000,000 – 10,000,000 people worldwide are currently living with Parkinson’s disease.  Approximately 60,000 Americans are diagnosed each year and this number does not reflect the estimated thousands that go undetected.  The combined direct and indirect cost of Parkinson’s, including treatment, social security payments and lost income from inability to work, is estimated to be nearly $25,000,000,000 per annum in the United States alone. Medication costs for an individual patient average $2,500 a year, with therapeutic surgery costing up to $100,000 per patient (source: Parkinson’s Disease Foundation).

The diagnosis of PD depends upon the presence of one or more of the four most common motor symptoms of the disease, which are: resting tremor, bradykinesia, rigidity and postural instability.  In addition, there are other secondary and non-motor symptoms that affect many people and are increasingly recognized by doctors as important to treating Parkinson’s.  Each person with Parkinson's will experience these symptoms differently.  For example, many people experience tremor as their primary symptom, while others may not have tremors, but may have problems with balance.  Also, for some people the disease progresses quickly, and in others it does not.

Primary Motor Symptoms:

Resting Tremor:  
About 70 percent of people with Parkinson’s experience a slight tremor in the early stage of the disease - either in the hand or foot on one side of the body, or less commonly in the jaw or face.  The tremor appears as a "beating" or oscillating movement.  Because the Parkinson's tremor usually appears when a person's muscles are relaxed, it is called "resting tremor."  This means that the affected body part trembles when it is not doing work, and it usually subsides when a person begins an action.  The tremor often spreads to the other side of the body as the disease progresses, but remains most apparent on the original side of occurrence.

Bradykinesia (Slow Movement):  Bradykinesia is the phenomenon of a person experiencing slow movements.  In addition to slow movements, a person with bradykinesia will probably also have incomplete movement, difficulty initiating movements and sudden stopping of ongoing movement.  People who have bradykinesia may walk with short, shuffling steps (this is called festination).  Bradykinesia and rigidity can occur in the facial muscles, reducing a person's range of facial expressions and resulting in a "mask-like" appearance.

Rigidity:  Rigidity, also called increased muscle tone, means stiffness or inflexibility of the muscles.  Muscles normally stretch when they move, and then relax when they are at rest.  In rigidity, the muscle tone of an affected limb is always stiff and does not relax, sometimes resulting in a decreased range of motion.  For example, a person who has rigidity may not be able to swing his or her arms when walking because the muscles are too tight.  Rigidity can cause pain and cramping.

Postural Instability (Impaired Balance and Coordination): People with Parkinson's disease often experience instability when standing or impaired balance and coordination.  These symptoms, combined with other symptoms such as bradykinesia, increase the chance of falling.  People with balance problems may have difficulty making turns or abrupt movements.  They may go through periods of "freezing," which is when a person feels stuck to the ground and finds it difficult to start walking.  The slowness and incompleteness of movement can also affect speaking and swallowing.

Secondary Motor Symptoms:

The secondary motor symptoms include those below, but not all people with Parkinson’s will experience all of these:

Stooped posture, a tendency to lean forward
Impaired fine motor dexterity and motor coordination
Impaired gross motor coordination
Poverty of movement (decreased arm swing)
Speech problems, such as softness of voice or slurred speech caused by lack of muscle control
Loss of facial expression, or "masking"
Micrographia (small, cramped handwriting)
Difficulty swallowing
Sexual dysfunction
Non-motor Symptoms

Non-motor symptoms of Parkinson’s, such as sleep problems and depression, can be, for many people, as troublesome as the primary movement symptoms of the disease.

The following is a list of non-motor symptoms of Parkinson's disease:

Dementia or confusion ementia
Sleep disturbances
Skin problems
Fear or anxiety
Memory difficulties and slowed thinking
Urinary problems
Fatigue and aching
Loss of energy
Compulsive behavior

Source: The Parkinson’s Disease Foundation, Jan. 2011