What Causes Parkinson's Disease?

What Causes Parkinson's Disease and are there any risk factors?

The underlying etiology (causative factors) that lead to Parkinson's disease are poorly understood. It is probably multifactorial, meaning that there are several factors which contribute to its development. Clues to the causes of Parkinson's disease can be found in the risk factors which are associated with the disease. Although most cases are sporadic, there does seem to be some genetic predisposition. People with a close relative with the disease are slightly more likely to develop the disease themselves, although the risk is still rather small. Likewise, it is known that older age and male gender are risk factors as the risk increases with age and is higher in men than women. There may also be some toxins or viruses, exposure to which may increase one's risk for Parkinson's.

Although the actual initial causes of Parkinson's Disease are poorly understood, the actual pathophysiology that occurs in the brains of patients is well described. For unknown reasons, abnormal clumps of protein build up in certain neurons (nerve cells) in the brain. These clumps are called Lewy Bodies. As the disease progresses, neurons in certain parts of the brain die. One of the most pronounced areas of damage in this disease is in a group of cells (nucleus) in the brain called the substantia nigra. These cells normally use dopamine as their neurotransmitter and are part of the basal ganglia, a collection of nuclei important for control and coordination of initiation of motor functions.

The death of these dopamine-secreting cells in the brain lead to imbalance and dysfunction of the basal ganglia, affecting motor system control. This imbalance is progressive, getting worse over time, and explains the motor symptoms (tremor, rigidity, etc.) that are common in patients with Parkinson's disease.

Although the cells of the substantia nigra is the most profoundly affected early, other areas of the brain can become affected with time, leading to imbalance in other systems and with other neurotransmitters (such as norepinephrine), leading to other late symptoms such as dementia and dysfunction of the autonomic nervous system.

Just as what causes Parkinson's Disease is not clear, why the dopamine containing cells of the substantia nigra are most affected by this disease is poorly understood. There is ongoing current research that aims to more clearly elucidate the underlying risk factors, pathophysiology and causes of Parkinson's Disease.