Further, we observed no obvious stratification of PMS cases using CHI3L1:CHI3L2 ratio, further indication that our cases were indeed all PMS cases (Hinsinger et al., 2015).Never the less, we observed no correlation between protein markers of neurodegeneration and ccf-mtDNA level or integrity; although this may reflect the late disease stage of our cases and the use of post-mortem CSF. Here, CHI3L2 is linked to premenstrual tension.