β-Amyloid PET and 123I-FP-CIT SPECT in Mild Cognitive Impairment at Risk for Lewy Body Dementia

Abstract

Objective: To determine the clinical phenotypes associated with the β-amyloid PET and dopamine transporter imaging (123I-FP-CIT SPECT) findings in mild cognitive impairment (MCI) with the core clinical features of dementia with Lewy bodies (DLB; MCI-LB).

Methods: Patients with MCI who had at least 1 core clinical feature of DLB (n = 34) were grouped into β-amyloid A+ or A- and 123I-FP-CIT SPECT D+ or D- groups based on previously established abnormality cut points for A+ with Pittsburgh compound B PET standardized uptake value ratio (PiB SUVR) ≥1.48 and D+ with putamen z score with DaTQUANT <-0.82 on 123I-FP-CIT SPECT. Individual patients with MCI-LB fell into 1 of 4 groups: A+D+, A+D-, A-D+, or A-D-. Log-transformed PiB SUVR and putamen z score were tested for associations with patient characteristics.

Results: The A-D+ biomarker profile was most common (38.2%), followed by A+D+ (26.5%) and A-D- (26.5%). The least common was the A+D- biomarker profile (8.8%). The A+ group was older, had a higher frequency of APOE ε4 carriers, and had a lower Mini-Mental State Examination score than the A- group. The D+ group was more likely to have probable REM sleep behavior disorder. Lower putamen DaTQUANT z scores and lower PiB SUVRs were independently associated with higher Unified Parkinson's Disease Rating Scale-III scores.

Conclusions: A majority of patients with MCI-LB are characterized by low β-amyloid deposition and reduced dopaminergic activity. β-Amyloid PET and 123I-FP-CIT SPECT are complementary in characterizing clinical phenotypes of patients with MCI-LB.

Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.

Figures

Figure 1. Distribution of Patients With MCI-LB Based on Global Cortical PiB SUVR and Putamen DaTQUANT z Scores

Scatterplot showing distribution of patients with mild cognitive impairment with Lewy bodies (MCI-LB) into quadrants of global cortical Pittsburgh compound B (PiB) standardized uptake value ratio (SUVR) and putamen DaTQUANT z scores with colored dots. Reference lines were 1.48 for global cortical PiB SUVR and −0.82 for putamen DaTQUANT z scores. Patients with MCI-LB with PiB SUVR ≥1.48 are identified with abnormal β-amyloid PET (A+). Patients with MCI-LB with putamen DaTQUANT z score <−0.82 are IDENTIFIED With abnormal 123I-FP-CIT SPECT (D+). A−D− = normal β-amyloid PET and normal 123I-FP-CIT SPECT in gray; A+D− = abnormal β-amyloid PET but normal 123I-FP-CIT SPECT in blue; A−D+ = normal β-amyloid PET but abnormal 123I-FP-CIT SPECT in orange, and A+D+ = abnormal β-amyloid PET and abnormal 123I-FP-CIT SPECT in green.

Figure 2. Illustrative Images

Bottom color bar represents cortical voxel-to-cerebellar retention ratio for β-amyloid PET. Right color bar represents normalized striatum-to-background ratio for 123I-FP-CIT SPECT. A−D− = normal β-amyloid PET and normal 123I-FP-CIT SPECT; A+D− = abnormal β-amyloid PET but normal 123I-FP-CIT SPECT; A−D+ = normal β-amyloid PET but abnormal 123I-FP-CIT SPECT; A+D+ = abnormal β-amyloid PET and abnormal 123I-FP-CIT SPECT.

Figure 3. Box Plots of UPDRS-III Scores in A and D Groups

Box plots show the Unified Parkinson’s Disease Rating Scale Part III (UPDRS-III) scores in patients with (A) negative β-amyloid PET (A−) and positive β-amyloid PET (A+) and (B) negative 123I-FP-CIT SPECT (D−) and positive 123I-FP-CIT SPECT (D+) in with mild cognitive impairment with Lewy bodies. PiB = Pittsburgh compound B; SUVR, standardized uptake value ratio.

Figure 4. Box Plots of Global Cortical PiB SUVRs and Putamen DaTQUANT z Scores Across 3 Groups

Box plots show the (A) global cortical Pittsburgh compound B (PIB) standardized uptake value ratios (SUVRs) and (B) putamen DaTQUANT z scores in patients with mild cognitive impairment with 1 core features (gray), 2 core features (orange), and 3 or 4 core features (blue).