The dementia is probably caused by the underlying mechanism.
The motor symptoms of Parkinson’s are caused by the loss of dopamine producing neurons in the motor cortex. The loss of those neurons for any reason would cause Parkinson style motor symptoms.
The cause of the loss of dopamine producing neurons in standard Parkinson’s is not understood, but appears to be related to a thing called Lewy bodies which are deposits of a protein called alpha-synuclein. The presence of Lewy bodies outside of the motor cortex is correlated with a disease called Lewy body dementia rather than Parkinson’s.
Most likely, there is a underlying process that causes neuron loss that slowly spreads. This process frequently starts in the motor cortex resulting in Parkinson’s, but sometimes starts elsewhere causing Lewy body dementia. Dementia in a person with Parkinson’s likely occurs when the process starts spreading beyond the motor cortex which effectively causes Lewy body dementia now that it is no longer isolated to the motor cortex.
My father passed from Lewy Body dementia. His brother died of Parkinson's. The diseases appear different in the order of symptoms, but are similar in the end.
Doing some research on the terminology, I guess motor system is the term I was looking for. I am not a biologist so I am not familiar with the terminology.
The motor symptoms of Parkinson’s are caused by the loss of dopamine producing neurons in the motor cortex. The loss of those neurons for any reason would cause Parkinson style motor symptoms.
The cause of the loss of dopamine producing neurons in standard Parkinson’s is not understood, but appears to be related to a thing called Lewy bodies which are deposits of a protein called alpha-synuclein. The presence of Lewy bodies outside of the motor cortex is correlated with a disease called Lewy body dementia rather than Parkinson’s.
Most likely, there is a underlying process that causes neuron loss that slowly spreads. This process frequently starts in the motor cortex resulting in Parkinson’s, but sometimes starts elsewhere causing Lewy body dementia. Dementia in a person with Parkinson’s likely occurs when the process starts spreading beyond the motor cortex which effectively causes Lewy body dementia now that it is no longer isolated to the motor cortex.