Causes


Parkinson's disease is caused by the failure of a group of nerve cells in the brain to produce adequate amounts of a chemical called dopamine. Dopamine is necessary for smooth, co-ordinated movement and muscle relaxation. We do not know why the cells cease producing dopamine.
 

Parkinson's disease is sometimes referred to as idiopathic, which means that the primary cause is unknown, in order to distinguish it from parkinsonism, which are the symptoms occurring from a known cause. Studies suggest that genetic factors are important in causing Parkinson's, although a recent one found that they are rarely critical in cases which develop after the age of fifty. Nevertheless, identifying genetic abnormalities that cause early-onset Parkinson's disease may help researchers learn more about the basic mechanisms of the disease itself. Even with some understanding of the abnormal biological mechanisms in the brain that cause Parkinson's disease, no one knows at this time how long it takes before nerve damage and dopamine loss trigger symptoms. At this time, the best guess is about five years.

The cause of Parkinson's disease remains a mystery. Most people who develop symptoms of primary Parkinson's disease have "Idiopathic Parkinson's Disease".
 

Patients may attempt to link the onset of Parkinson symptoms with some acute trauma of an accident, surgery, or extreme emotional distress. Most neurologists discount any direct link; a traumatic event might trigger symptoms before they would otherwise manifest, but this should not be confused with actual causation of the Parkinsonism. After all, most people who experience these traumatic events do not develop a movement disorder such as Parkinson’s disease.

There are also secondary forms of Parkinsonism. Some drugs interfere with the brain's metabolism of dopamine, and prolonged use can produce Parkinson features.

While there are isolated instances of a high incidence of Parkinson disease in certain families, there is at present no definitive research that identifies an actual gene linked to Idiopathic Parkinson's Disease (the most common form of PD).

The predominant neuropathological feature of Parkinson's disease is characterized by a loss of the neuromelanin-containing dopaminergic cells of the substantia nigra.

It is convenient to think of the brain in evolutionary terms:

·       The higher brain is concerned with intellect and advanced skills, such as movement and manual dexterity, as well as the reception of the senses.

·       The function of the cerebellum is more primitive; it partially encircles the brain system, symbolically suggesting its role as a stabilizer or moderator, smoothing movements and actions, and regulating the irregular impulses of the higher cortex into controlled activity, while maintaining balance and posture.

·       Between the cerebellum and the proximal extent of the spinal cord are the basal ganglia. These are amongst the most primitive areas of the brain and contain some of the basic regulatory centres for autonomic function as well as co-ordination.

In one area of the basal ganglia lies a thin band of pigmented neurones (the substantia nigra) degeneration of which results in the onset of Parkinoson’s disease. It seems however not the primary loss of these cells themselves that is the fundamental pathology, but the consequent loss of their neurotransmitter, dopamine. The eventual result is a degeneration of the dopaminergic nigrostriatal pathway, although it is estimated that 80% of dopamine in the striatum is lost before symptoms become clinically apparent.

 

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