Neuropathological Alterations in Alzheimer Disease

  1. Bradley T. Hyman1
  1. 1Alzheimer Research Unit of the MassGeneral Institute for Neurodegenerative Disease, Department of Neurology of the Massachusetts General Hospital, and Harvard Medical School, Charlestown, Massachusetts 02129-4404
  2. 2C.S. Kubik Laboratory for Neuropathology, Massachusetts General Hospital, Boston, Massachusetts 02114
  3. 3Department of Neuroscience and Department of Pathology, University of California-San Diego School of Medicine, La Jolla, California 92093-0624
  1. Correspondence: bhyman{at}partners.org

Abstract

The neuropathological hallmarks of Alzheimer disease (AD) include “positive” lesions such as amyloid plaques and cerebral amyloid angiopathy, neurofibrillary tangles, and glial responses, and “negative” lesions such as neuronal and synaptic loss. Despite their inherently cross-sectional nature, postmortem studies have enabled the staging of the progression of both amyloid and tangle pathologies, and, consequently, the development of diagnostic criteria that are now used worldwide. In addition, clinicopathological correlation studies have been crucial to generate hypotheses about the pathophysiology of the disease, by establishing that there is a continuum between “normal” aging and AD dementia, and that the amyloid plaque build-up occurs primarily before the onset of cognitive deficits, while neurofibrillary tangles, neuron loss, and particularly synaptic loss, parallel the progression of cognitive decline. Importantly, these cross-sectional neuropathological data have been largely validated by longitudinal in vivo studies using modern imaging biomarkers such as amyloid PET and volumetric MRI.

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