Parkinson's Disease Blog

Although James Parkinson described the disease nearly two centuries ago and research has been ongoing ever since, the underlying cause — the factor that sets Parkinson’s disease (PD) in motion — is still unknown. A number of theories are under discussion and research, any one of which may lead to the breakthrough in managing symptoms or even curing the disease. The medical community has also made progress in assessing risk factors — some more common than others. In this chapter we cover these potential causes and risk factors so you can better understand them as the hunt for a cure continues.

The underlying event behind the onset of PD is a loss of neurons (nerve cells) in the substantia nigra region of the brain. These neurons normally produce dopamine, a neurotransmitter that helps the brain communicate with other parts of the body, telling them to perform common movements (such as walking, handling objects, and maintaining balance) almost automatically.

PD is a little like diabetes because in both diseases:

• You lose a vital chemical (insulin in diabetes; dopamine in PD).
• The chemicals are essential to the body’s ability to function properly.
• The chemicals can be replaced.

Of course, the diseases are more complex than that, but you get the idea. As we age, all of us lose dopamine-producing neurons, which results in the slower, more measured movements. But the decline of dopamine in people with Parkinson’s (PWP) is not normal.

Why PD targets the substantia nigra at the stem of the brain remains a mystery. But the damage results in abnormal protein deposits that can disrupt the normal function of the cells in that area. These protein clumps are called Lewy bodies, named for Freiderich H. Lewy, the German physician who discovered and documented them in 1908. The presence of Lewy bodies within the substantia nigra is associated with a depletion of the brain’s normal supply of dopamine. For this reason, their presence is one of the pathological hallmarks of PD (although Lewy bodies are present in other disorders).

In reality, Lewy bodies have been found in other parts of the brain affected by PD, which suggests that the problem may be more widespread. This more extensive pathology may explain the occurrence of non-motor and levodopaunresponsive symptoms. Nevertheless, researchers still don’t know whether Lewy bodies cause the damage to the nerve cells or are a by-product of damage caused by another factor.

Theories on causes abound — family history, environment, occupation, and so on. Today’s researchers generally agree, however, that the onset of PD is a multi-factorial process; that is, several conditions are at play in the onset of PD rather than one specific and single cause. But the true causes behind the onset of PD in one person and not another — in one family member and not another — are unknown.