Brain connectivity in neurodegenerative diseases--from phenotype to proteinopathy.
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2014-10-21
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Abstract
Functional and structural connectivity measures as assessed by means of functional and diffusion MRI are emerging as potential intermediate biomarkers for Alzheimer disease AD and other disorders This Review aims to summarize current evidence that connectivity biomarkers are associated with upstream and downstream disease processes molecular pathology and clinical symptoms respectively in the major neurodegenerative diseases The vast majority of studies have addressed functional and structural connectivity correlates of clinical phenotypes confirming the predictable correlation with topography and disease severity in AD and frontotemporal dementia In neurodegenerative diseases with motor symptoms structural but to date not functional connectivity has been consistently found to be associated with clinical phenotype and disease severity In the latest studies the focus has moved towards the investigation of connectivity correlates of molecular pathology Studies in cognitively healthy individuals with brain amyloidosis or genetic risk factors for AD have shown functional connectivity abnormalities in preclinical disease stages that are reminiscent of abnormalities observed in symptomatic AD This shift in approach is promising and may aid identification of early disease markers establish a paradigm for other neurodegenerative disorders shed light on the molecular neurobiology of connectivity disruption and ultimately clarify the pathophysiology of neurodegenerative diseases