What cause the impairment of neurons in parkinson's disease?

Unknown: In the etiology of this disease toxic substances (like heavy metals, specific chemicals) infectious e.g. Viral) genetic and environmental factors have been implicated but no definite theory exists.

Lewy Bodies: Polymers of a-synuclein protein form into "clumps" (intraneuronal inclusions) due to faulty "trash removal" processes in the neurons. As a result, cellular activity is disrupted. Other problems, such as oxidative stress causing mitochondria damage (energy producing portion of cell) lead to programmed cell death, or "apoptosis." many other facets of this cascade of problems are yet to be understood.