Neuroimaging of Alzheimer

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Neuroimaging of Alzheimers Disease

• Kim Kinard

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Alzheimers Disease (AD)

• Progressive neurodegenerative disorder
• deterioration in cognition, function, and
  behavior
• Most common cause dementia in elderly
• 4 million in U.S.
• 30 million worldwide
• Female to male 31
• 100 billion per year in U.S.

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Pathology and Etiology

• Initial damage of neurons in temporal lobes and
  later in neocortex
• Extracellular beta amyloid plaques and
  intracellular neurofibrillary tangles (tau
  protein)
• Plaque buildup induces inflamation causing injury
  in hippocampus and cerebral cortex

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Clinical Diagnosis

• Accuracy can exceed 90
• Detailed history, physical, mental status
  examination, and neurologic assessment
• Rule out hypothyroidism, vitamin B12 deficiency,
  reversible causes of dementia

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DSM IV Criteria

• memory impairment
• 2 of 4
• Aphasia
• Apraxia
• Agnosia
• Disturbance executive functioning

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Differential Diagnosis

• Alzheimer Disease (50-70)
• Vascular dementia (15)
• Frontotemporal dementia (5-10)
• Lewy Body disease (25)
• Normal Pressure Hydrocephalus (NPH)
• Depression
• Intracranial Mass

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Imaging Studies

• Stuctural CT and MR recommended for routine
  evaluation of AD
• Functional PET and SPECT demonstrate physiologic
  changes in brain

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MR vs. CT

• Low specificy and sensitivity
• MR preferred over CT
• Assess degree of Medial Temporal Lobe Atrophy
• Amygdala, Hippocampus, Parahippocampal gyrus
• Rule out other causes dementia

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AD vs. Other Dementias

• NPH holoventricular enlargement out of
  proportion to sulcal enlargement dementia,
  apraxia, incontinence
• Generalized atrophy sulcal and ventricular
  findings concordant
• Vascular dementia multiple areas of high signal
  intensity on MR stepwise decline, smokers, HTN,
  diabetes

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Alzheimer Disease
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NPH
12
Generalized Atrophy
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Vascular Dementia
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MR uses in AD

• Quantitative hippocampal volume analysis better
  with MR than CT
• Tracing-thresholding method
• Tracing operator outlines borders of interest
• Thresholding minimum gray-scale value permits
  boundary detection
• sensitivity of 82 and specificity of 80 (N220)
• FIGURE 9

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Functional Imaging Modalities

• SPECT and PET
• Vascular dementia
• Frontotemporal dementia
• Lewy Body
• depression

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SPECT imaging

• Brain uptake of technetium 99m-based
  lipid-soluble radionuclide
• 89 sensitivity and 80 specificity for AD
• Bilateral posterior perfusion abnormality
  associated with AD
• Frontal perfusion deficit associated with
  frontotemporal dementia
• Patchy uptake pattern associated with vascular
  dementia

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SPECT imaging
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PET imaging

• FDG and blood flow
• Deficits in temporoparietal metabolism seen in
  patients with AD
• Sparing of basal ganglia, thalamus, cerebellum,
  and primary sensorimotor complex
• Sensitivity 87-96, 73 specificity
• Figure 13

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PET imaging

• Frontotemporal dementias decreased uptake in
  frontal and anterior temporal regions
• Depression normal scan
• Vascular patchy defects in central white matter
• Lewy body deficits in occipital lobes and
  cerebellum

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PET imaging

• New tracer for PET
• FDDNP
• Fluoroethyl methyl amino naphtylethylidene
  malononitrile
• Targets amyloid beta senile plaques and
  neurofibrillary tangles
• Long retention times in hippocampus

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Cost of Imaging

• CT 300-600
• MRI 860-1200
• SPECT 1900
• PET 1900-3500

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Conclusion

• Clinical criteria have high sensitivity and
  specificity (gt90)
• Imaging will help to exclude other causes of
  dementia
• Standard of care CT or MR
• FDG PET highest prognostic utility for AD 2-3
  years before fully symptomatic

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References

• Jack CR et al. MR Imaging-Based Volume
  Measurements of the Hippocampal Formation and
  Anterior Temporal Lobe Validation Studies.
  Neuroradiology. Volume 176. No. 1 pp. 205-209.
• Lehericy et al. Magnetic Resonance Imaging of
  Alzheimers Disease. Eur Radiol (2007) 17
  347-362.
• Petrella, et al. Neuroimaging and Early Diagnosis
  of Alzheimer Disease A Look to the Future.
  Radiology 2003 226 315-336.
• Zakzanis, Graham, and Campbell. A Meta-Analysis
  of Structural and Functional Brain Imaging in
  Dementia of the Alzheimers Type A Neuroimaging
  Profile. Neuropsychology Review, Vol. 13, No. 1,
  March 2003.