The Blood–Brain Barrier in Cognitive Decline and Alzheimer’s Disease

The neurovascular unit is a multicellular organ that has attracted recent attention as a key microvascular regulator of cerebral blood flow and blood–brain barrier permeability that is implicated in homeostatic and pathological processes impacting cognitive function. Breakdown of the blood–brain barrier invariably causes brain tissue damage and dysfunction due to influx of toxic blood proteins, cells, ions and metals. Clinical studies employing markers of blood–brain barrier permeability suggest an important role in vascular and neurodegenerative dementias. The chapter discusses how the introduction of new neuroimaging and biomarker technologies has opened new pathways of investigation into the blood–brain function in Alzheimer’s disease.