Combined Use of 123i-fp-cit Spect and 123i-mibg Scintigraphy for Differentiation of Progressive Supranuclear Palsy Subtypes and Parkinson's Disease

Abstract Background:This study was undertaken to investigate the utility of 123I-ioflupane (123I-FP-CIT) single photon emission computed tomography (SPECT), 123I-metaiodobenzylguanidine (123I-MIBG) scintigraphy and both of these to differentiate among progressive supranuclear palsy (PSP), including typical cases and other subtypes, and Parkinson’s disease (PD).Methods: Twenty-five patients with typical PSP (Richardson's syndrome; PSP-RS), 14 atypical ones (PSP-variants; PSP-V) and 42 PD who underwent both 23I-FP-CIT SPECT and 123I-MIBG scintigraphy within short intervals were enrolled. Specific binding ratio (SBR) of the striatum and midbrain and anteroposterior and asymmetry ratio of the striatal SBR on 123I-FP-CIT SPECT and heart-to-mediastinum (H/M) ratio and washout rate (WR) on 123I-MIBG scintigraphy were used as quantitative measures. The classifier performance based on adaptive boosting was evaluated using five-fold cross-validation for these measures.Results: Midbrain SBR and the striatal anteroposterior ratio were statistically lower in PSP-RS than PD. On the other hand, there were no significant differences in any other quantitative measures among PSP-RS, PSP-V and PD. Striatal and midbrain SBRs and anteroposterior ratio of PSP-V were approximately in-between those of PSP-RS and PD. PD showed the lowest early and delayed H/M ratios and highest WR of any group. The combination of 123I-FP-CIT and 123I-MIBG was useful in discriminating PSP-RS and PSP-V from PD, while 123I-FP-CIT was superior to 123I-MIBG in differentiating PSP-RS from PSP-V.Conclusion: The combination of 123I-FP-CIT SPECT and 123I-MIBG scintigraphy, rather than either alone, may be a useful differential diagnostic tool to differentiate patients with PSP-RS, PSP-V and PD.