Fractal Analysis in Neurodegenerative Diseases

Abstract

Neurodegenerative diseases are defined by progressive nervous system dysfunction and death of neurons. The abnormal conformation and assembly of proteins is suggested to be the most probable cause for many of these neurodegenerative disorders, leading to the accumulation of abnormally aggregated proteins like, for example, amyloid-beta (A beta) (Alzheimer's disease and vascular dementia), tau protein (Alzheimer's disease and frontotemporal lobar degeneration), alpha-synuclein (Parkinson's disease and Lewy body dementia), polyglutamine expansion (Huntington disease), or prion proteins (Creutzfeldt-Jakob's disease). An aberrant gain-of-function mechanism toward excessive intraparenchymal accumulation thus represents a common pathogenic denominator in all these proteinopathies. Moreover, depending upon the predominant brain area involvement, these different neurodegenerative diseases lead to either movement disorders or dementia syndromes, although the underlying mechanism(s) can sometimes be very similar, and at other occasions, clinically similar syndromes have quite distinct pathologies. Non-Euclidean image analysis approaches such as fractal dimension (FD) analysis have been applied extensively in quantifying highly variable morphopathological patterns, as well as many other connected biological processes; however, their application to understand and link abnormal proteinaceous depositions to other clinical and pathological features composing these syndromes are yet to be clarified. Thus, this chapter aims to present the most important applications of FD in investigating the clinical-pathological spectrum of neurodegenerative diseases.