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 (18)F-fluorinated-N-3-fluoropropyl-2-b-carboxymethoxy-3-b-(4-iodophenyl) nortropane ([(18)F]FP-CIT) PET differs according to the metabolic subtype of multiple system atrophy (MSA) as assessed by [(18)F]FDG PET.

This retrospective study included 50 patients with clinically diagnosed MSA who underwent [(18)F]FP-CIT and [(18)F]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 [(18)F]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.

Of the 50 patients, 13 presented with MSA-Pm, 16 presented with MSA-mixedm, and 21 presented with MSA-Cm. 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.

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.