Different loss of dopamine transporter according to subtype of multiple system atrophy

The aim of 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. 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-P_m (striatal hypometabolism only), MSA-mixed_m (both striatal and cerebellar hypometabolism), and MSA-C_m (cerebellar hypometabolism only). The subregional glucose metabolic ratio (MR_gluc), subregional DAT binding ratio (BR_DAT), and intersubregional ratio (ISR_DAT; defined as the BR_DAT ratio of one striatal subregion to that of another striatal subregion) were compared according to metabolic subtype. Of the 50 patients, 13 presented with MSA-P_m, 16 presented with MSA-mixed_m, and 21 presented with MSA-C_m. The BR_DAT of all striatal subregions in the MSA-P_m and MSA-mixed_m groups were significantly lower than those in the MSA-C_m group. The posterior putamen/anterior putamen ISR_DAT and anterior putamen/ventral striatum ISR_DAT in the MSA-P_m and MSA-mixed_m groups were significantly lower than those in the MSA-C_m group. Patients with MSA-P_m and MSA-mixed_m showed more severe DAT loss in the striatum than patients with MSA-C_m. Patients with MSA-C_m had more diffuse DAT loss than patients with MSA-P_m and MSA-mixed_m. (orig.)