Neuropathology of Parkinson’s Disease

Abstract

Parkinson’s disease (PD), one of the most frequent neurodegenerative disorders, is a progressive multiorgan proteinopathy caused by misfolded α-synuclein (α-syn) with variegated motor and nonmotor symptoms owing to a spreading process of synaptic and neuronal loss. Deposition of abnormal α-syn, the major protein marker of PD and other synucleinopathies, occurs first in presynaptic terminals and causes nerve cell loss and disturbance of neurotransmission via axonal degeneration. Morphological features of PD are degeneration of the dopaminergic striatonigral system, responsible for the core motor deficits, and a multifocal involvement of the central, peripheral, and autonomic nervous system and other organs associated with widespread occurrence of Lewy bodies in neurons and dystrophic Lewy neurites in cell processes. The resulting striatal dopamine deficiency and other complex biochemical deficits cause the heterogeneous clinical picture of the disease. Recent research has provided insights into the development, spreading, and staging of α-syn and its relation with Lewy pathology and clinical deficits. However, many challenges remain including the role of α-syn in the course of neurodegeneration, its interaction with other proteins and its prion-like spread and progression of the disease. Many factors in the pathogenesis of PD and the causes of neuronal cell death are still poorly understood. Although genetic and experimental models have contributed to exploring the pathomechanisms of PD, there is still lack of an optimal animal model, and the etiology of this incurable disease is far from being elucidated.