Which imaging studies are indicated in the workup of dementia with Lewy bodies (DLB)?

Updated: Aug 08, 2019
  • Author: Howard A Crystal, MD; Chief Editor: Jasvinder Chawla, MD, MBA  more...
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Answer

Because vascular dementia can cause symptoms and signs similar to those of DLB, brain magnetic resonance imaging (MRI) is indicated to distinguish DLB from vascular dementia. Patients with vascular dementia often have white matter lesions on MRI scans, whereas patients with DLB do not. [15]

Patients with DLB usually have less hippocampal atrophy than do patients with Alzheimer disease (but more than control subjects), although whether this difference is clinically useful is under investigation, as is the diagnostic utility of functional imaging. MRI is superior to computed tomography (CT) scanning in identifying this atrophy.

SPECT or positron emission tomography (PET) scanning may show decreased occipital lobe blood flow or metabolism in DLB but not in Alzheimer disease. SPECT using ligands that bind to the dopamine transporter molecule (eg,123 I-beta-CIT) has been used to suggest the diagnosis of DLB. Abnormal dopamine transporter scans have been shown to have a sensitivity of over 75% and a specificity of over 90% for DLB. [16]

A study by Lim et al using SPECT scanning with123 I-beta- carbomethoxy-3beta-(4-fluorophenyl) tropane (123 I-beta-CIT), as well as PET scanning with18 F-fluorodeoxyglucose (18 F-FDG), in 14 patients with a clinical diagnosis of DLB and 10 with Alzheimer disease found that relative preservation of the mid- or posterior cingulate gyrus (cingulate island sign) had 100% specificity for DLB. SPECT and PET scanning each appeared useful for the diagnosis of DLB, but SPECT provided more robust results than did PET. [17]

PET imaging with Pittsburgh Compound B showed that amyloid deposition in clinically diagnosed patients with DLB was similar to that in the patients with Alzheimer disease. However, amyloid binding was less in patients with dementia in Parkinson disease. Findings of these studies suggest that the presence of amyloid accelerates dementia in Lewy body disorders but has little influence on its nature. [18, 19]

Until disease-modifying therapies that are specific to DLB or Alzheimer disease are developed, metabolic imaging studies to enhance the accuracy of the diagnosis are rarely needed.


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