A significant difference was found between the LBD patient group and CG of the present study, where it was decreased, with a strong trend towards a decreased quotient between the MSA patient group and CG, which could suggest that synucleinopathy patients have a larger BBB and/or C3 complement transport disruption, or CSF complement activation than 4RT tauopathy patients (Song et al. 2011; Al-Bachari et al. 2020). Here, C3 is linked to multiple system atrophy.