Different Loss of Dopamine Transporter according to Metabolic Subtypes of Multiple System Atrophy

Abstract

Purpose The aimof this study was to evaluate whether striatal dopamine transporter (DAT) loss as measured by 18F-fluorinated- N-3-fluoropropyl-2-b-carboxymethoxy-3-b-(4- iodophenyl) nortropane ([18F]FP-CIT) PET differs according to the metabolic subtype of multiple system atrophy (MSA) as assessed by [18F]FDG PET. Methods This retrospective study included 50 patients with clinically diagnosed MSA who underwent [18F]FP-CIT and [18F]FDG brain PET scans. The PET images were analysed using 12 striatal subregional volume-of-interest templates (bilateral ventral striatum, anterior caudate, posterior caudate, anterior putamen, posterior putamen, and ventral putamen). The patients were classified into three metabolic subtypes according to the [18F]FDG PET findings: MSA-Pm (striatal hypometabolism only), MSA-mixedm (both striatal and cerebellar hypometabolism), and MSA-Cm (cerebellar hypometabolism only). The subregional glucose metabolic ratio (MRgluc), subregional DAT binding ratio (BRDAT), and intersubregional ratio (ISRDAT; defined as the BRDAT ratio of one striatal subregion to that of another striatal subregion) were compared according to metabolic subtype. Results Of the 50 patients, 13 presented with MSA-Pm, 16 presented with MSA-mixedm, and 21 presented with MSACm. The BRDAT of all striatal subregions in the MSA-Pm and MSA-mixedm groups were significantly lower than those in the MSA-Cm group. The posterior putamen/anterior putamen ISRDAT and anterior putamen/ventral striatum ISRDAT in the MSA-Pm and MSA-mixedm groups were significantly lower than those in the MSA-Cm group. Conclusion Patients with MSA-Pm and MSA-mixedm showed more severe DAT loss in the striatum than patients with MSA-Cm. Patients with MSA-Cm had more diffuse DAT loss than patients with MSA-Pm and MSA-mixedm.