I-FP-CIT SPECT Findings and Its Clinical Relevance in Prodromal Dementia with Lewy Bodies

Purpose: Evidence for the prodromal stage of dementia with Lewy bodies (DLB) is very limited. To address this issue, we investigate the I-FP-CIT SPECT measure of dopamine transporter binding finding and its clinical relevance.

Methods: We enrolled subjects into a prodromal DLB group (PRD-DLB) (n = 20) and clinical DLB group (CLIN-DLB) (n = 18) and compared these groups with an Alzheimer's disease control group (AD) (n = 10). PRD-DLB was defined as patients having the non-motor symptoms associated with Lewy body disease (LBD) [i.e. REM sleep behavior disorder (RBD), olfactory dysfunction, autonomic dysfunction, and depression] and showing characteristic diffuse occipital hypometabolism in F-FDG PET. CLIN-DLB was defined as patients fulfilling the established criteria of probable DLB. Striatal specific binding ratio (SBR) of I-FP-CIT SPECT was used for objective group comparisons. The correlations between SBR and cognitive function (MMSE), motor symptoms (UPDRS3), and duration of LBD-associated non-motor symptoms were compared between the two DLB groups.

Results: Mean SBR scores of both PRD-DLB and CLIN-DLB were significantly lower than those of AD. No correlation was found between SBR and MMSE scores. Both in the CLIN-DLB and total DLB groups, SBR scores were negatively correlated with UPDRS3 scores, whereas no correlation was found in PRD-DLB. Among the LBD-related non-motor symptoms, duration of olfactory dysfunction, and RBD demonstrated negative correlation with SBR scores in PRD-DLB.

Conclusion: I-FP-CIT SPECT may play a role for detecting DLB among the subjects in prodromal stage. During this stage, long-term olfactory dysfunction and/or RBD may indicate more severe degeneration of the nigro-striatal dopaminergic pathway.