Parkinson's Disease Causes
Parkinson's disease occurs when nerve cells, or neurons, in an area of the brain known as
the substantia nigra die or become impaired. Normally, these neurons produce an important
brain chemical known as dopamine. Dopamine is a 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 abnormal nerve firing patterns within the brain that cause impaired
movement. Studies have shown that most Parkinson's patients have lost 60 to 80 percent or
more of the dopamine-producing cells in the substantia nigra by the time symptoms appear.
Recent studies have shown that people with Parkinson's Disease also have loss of the nerve
endings that produce the neurotransmitter norepinephrine. Norepinephrine, which is closely
related to dopamine, is the main chemical messenger of the sympathetic nervous system, 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 help explain several of the
non-motor features seen in Parkinson's Disease, including fatigue and abnormalities of
blood pressure regulation.
Genctic Causes of Parkinson's Disease
Scientists have identified several genetic mutations associated with
Parkinson's Disease, and many more genes have been tentatively linked to the disorder.
Studying the genes responsible for inherited cases of Parkinson's Disease can help
researchers understand both inherited and sporadic cases. The same genes and proteins that
are altered in inherited cases may also be altered in sporadic cases by environmental
toxins or other factors. Researchers also hope that discovering genes will help identify
new ways of treating Parkinson's Disease.
Viruses as a possible cause for Parkinson's Disease
Viruses are another possible environmental trigger for Parkinson's
Disease. People who developed encephalopathy after a 1918 influenza epidemic were later
stricken with severe, progressive Parkinson's-like symptoms. A group of Taiwanese women
developed similar symptoms after contracting herpes virus infections. In these women, the
symptoms, which later disappeared, were linked to a temporary inflammation of the
Other Research into Parkinson's Disease Causes
Other research suggests that the cell's protein disposal system may fail
in people with Parkinson's Disease, causing proteins to build up to harmful levels and
trigger cell death. Additional studies have found evidence that clumps of protein that
develop inside brain cells of people with Parkinson's Disease may contribute to the death
of neurons, and that inflammation or overstimulation of cells (because of toxins or other
factors) may play a role in the disease. However, the precise role of the protein deposits
remains unknown. Some researchers even speculate that the protein buildup is part of an
unsuccessful attempt to protect the cell. While mitochondrial dysfunction, oxidative
stress, inflammation, and many other cellular processes may contribute to Parkinson's
Disease, the actual cause of the dopamine cell death is still undetermined.