Prion disease is a spectrum disease. Alzheimer’s disease and Parkinson’s disease are the most common human forms of prion disease. Alzheimer’s disease and Creutzfeldt jakob disease (CJD) are the common diagnoses when the primary symptom is dementia.
Alzheimer’s disease and CJD are the common diagnoses when the primary symptom is dementia. Parkinson’s disease is the common diagnoses when the primary symptom is a movement disorder. Some victims exhibit both symptoms.
Alzheimer’s disease begins in the hippocampus, which controls memory. Parkinson’s disease initially affects nerve cells deep within the brain called the basal ganglia and the substantia nigra — the region of the brain that controls movement.
Parkinson’s disease is the second most common diagnosis in the prion spectrum. It’s estimated that between 7-10 million people around the world have Parkinson’s disease today.
The US National Institute for Neurological Disorders and Stroke (NINDS) estimated in a 2006 report that about 50,000 new cases of Parkinson’s disease are diagnosed in the US each year, and the total number of cases in the US is at least 500,000. The true prevalence (total number of cases) of Parkinson’s disease is difficult to assess, because the disease is typically not diagnosed until the disease process is already far advanced. Therefore the actual number of Americans with the disease is almost certainly higher than the diagnostic numbers would suggest.
Worldwide numbers are difficult to obtain, but in industrialized countries the prevalence of Parkinson’s disease is about 1 percent for people over 60, with estimates of up to 4 percent for people in the highest age groups (de Lau & Breteler 2006). The risk of developing Parkinson’s disease rises sharply with age after the age of 60, so the number of cases is likely to grow significantly as populations become older throughout the world. In the US, for example, Dorsey et al (2007) estimated that the prevalence will at least double by 2030.
Parkinson’s disease mostly affects older people but it can occur at any age. It results from the gradual degeneration of nerve cells in the portion of the midbrain that controls body movement. The first signs are often barely noticeable—a feeling of weakness or stiffness in one limb or a fine trembling of one hand. Eventually, the shaking worsens and spreads. Muscles stiffen. Balance and coordination deteriorate. Depression and other mental or emotional problems are common as the disease progresses.
Parkinson’s disease usually begins between the ages of 50 and 65. It is slightly more common in men than women.
The protein alpha-synuclein plays a critical role in the pathogenesis of Parkinson’s disease. Alpha-synuclein accumulates in the brains of patients with Parkinson’s disease. It starts in a region of the lower brain called medulla oblongata from where it spreads upwardly toward midbrain and cortical areas.
Like prion diseases, misfolded alpha-synuclein and tau protein associated with Parkinson’s disease and Alzheimer’s disease, respectively, have been reported in skin tissues of patients with these conditions. Skin could serve as a screen for early diagnosis, but also for monitoring the accumulation of the misfolded proteins in the brain of these neurodegenerative diseases. It also could be further confirmation that all cell tissue and bodily fluids are infectious.
The basal ganglia area of the brain regulates body movements. Its cells require a proper balance of dopamine and acetylcholine, both involved in the transmission of nerve impulses. In Parkinson’s, cells that produce dopamine begin to degenerate, which upsets the balance of these neurotransmitters.
Michael J. Fox has bravely become the most famous spokesperson for victims of the disease. His work has generated a great deal of resources for research.
Fox and a few other cast mates from his early career in Vancouver all contracted Parkinson’s disease around the same age and were diagnosed around the same time. The connection was supposedly investigated, but no connection was announced. That does not rule out a correlation. They all shared the same air, water and food, which are pathways for prion disease.
If prions play a role in Parkinson’s disease pathology, as the Nobel-Prize winner Stanley Prusiner claims, the disease is likely transmissible just like the other forms of Transmissible Spongiform Encephalopathy (TSE)–again with the emphasis on the word transmissible. Since Parkinson’s doesn’t seem to be as deadly as the other forms of prion disease, it deserves an asterisk in some conversations. The variation could be a mutation in the prion or the genetic makeup of the victim.
Another theory is that the difference in Parkinson’s is found in the genetics of the host. Some people may be more resistant to prion disease than others. Koreans and Japanese researchers, for example, believe that there is a genetic predisposition to prion disease, which makes some races more vulnerable than others. If that’s true, then Parkinson’s disease patients may represent a genetic strain that is the antithesis to that research.
