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

OBJECTIVE: To determine the clinical phenotypes associated with the amyloid-β PET and dopamine transporter imaging (123 I-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 one core clinical feature of DLB (n=34) were grouped into β-amyloid A+ or A- and 123 I-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 123 I-FP-CIT SPECT. Individual MCI-LB patients fell into one of four 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%). Least common was A+D- biomarker profile (8.8 %). The A+ group was older, had a higher frequency of APOE ε4 carriers, and a lower MMSE score than the A- group. The D+ group was more likely to have probable rapid eye movement sleep behavior disorder. Lower putamen DATQUANT z-scores and lower PiB SUVRs were independently associated with higher Unified Parkinson Disease Rating Scale (UPDRS)-III scores.

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