The substantia nigra is part of the brainstem. The loss of cells is confined to pigmented, dopamine-containing cells. Calmodulin is involved in calcium-regulation. The role of calmodulin , and the vulnerability of dopamine cells lacking-calmodulin to die prematurely is, at this time, unknown. In PD, but not the PD-like diseases, the loss of cells in the brainstem is accompanied by Lewy bodies.
Lewy bodies are large relative to the cell.
PD affects one million Americans . Lewy bodies occur in dopamine and non-dopamine cells outside the brainstem . PD-dementia is characterized by a loss of memory and a marked decline in intellectual and cognitive abilities. At autopsy the cortical and brainstem cells of PD-dementia patients contain Lewy bodies. Diffuse Lewy Body Disease is PD beginning with memory loss and a decline in intellectual and cognitive abilities rather than PD beginning with rigidity, tremor, and slowness of movement.