Case of the Month: December, 2011 Page 4

Answer: A. 1:3

Discussion Points:

  • This case represents an example of Alzheimer Disease where there is discordant results  between FDG-PET and volumetric MRI
  • In 2000, 4 million people were affected by Alzheimer Disease
  • With aging “baby boomer” population, total US prevalence expected to increase to 20 million by year 2025
  • Age is the greatest risk factor for AD, prevalence of AD over age 60 = 1:10,000 and over age 85 = 1:3
  • Pathologic diagnosis of AD demonstrates characteristic B-Amyloid plaques in extracellular spaces throughout cerebral cortex and neurofibrillary tangles within neurons of the hippocampus
  • FDG-PET can differentiate AD from other forms of dementia:
    • Frontotemporal Dementia: decreased metabolism of frontal/temporal lobes
    • Multi-infarct Dementia: discrete nonpaired foci of decreased metabolism
    • Lewy-Body Disease: decreased metabolism includes occipital lobes
    • NPH: enlarged lateral ventricles showing no activity
  • AD treatment with Acetylcholinesterase inhibitors and NMDA receptor antagonists may mildly increase cognition or delay deficits up to 9-12 months
  • Novel PET diagnostic imaging technique involving direct radiolabelled binding of amyloid plaques is currently in Phase 3 clinical trials with reported high sensitivity and specificity


  • Prusiner.Neurodegenerative Diseases and Prions.NEJM. May 2001
  • Castillo. Neuroradiology Companion. 3rd ed. 2006
  • Osborn. Diagnostic Imaging: Brain. 2004
  • Clark. Florbetapir-PET for Imaging B-Amyloid Pathology.JAMA. January 2011


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