Overview of Neurodegenerative Disorders and Susceptibility Factors in Neurodegenerative Processes

The classification of neurodegenerative disorders includes human diseases that vary significantly in terms of their incidence, clinical presentation, and prognosis. All of these disorders, however, share the pathological feature of a progressive degenerative process that initially impairs neuronal function and ultimately leads to frank neurodegeneration and brain atrophy. Interestingly, neurodegenerative diseases also have in common another (besides neuronal loss) pathological trait, which is the accumulation of proteinaceous deposits. This intriguing feature may reflect dysfunction of protein-processing mechanisms, involving, for example, proteasomal and/or autophagic degradation pathways. The vast majority of cases of neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases, are idiopathic and sporadic. The likely involvement of genetic, environmental, and age-related culprits in disease pathogenesis justifies the appellation of complex disorders. Environmental contribution could arise from factors and mechanisms that include toxic exposures, lifestyle habits (e.g., food consumption and exercising), use of medications (e.g., cholesterol-lowering and anti-inflammatory drugs), and epigenetic modifications.