CHI3L1 and primary progressive multiple sclerosis: The mean CSF CHI3L1 levels for the different types of MS were as follows: 107.37 ng/ml (SD = 19.23) for relapsing-remitting MS (RRMS), 244.27 ng/ml (SD = 52.99) for progressive MS (PMS), 256.00 ng/ml (SD = 70.50) for primary progressive MS (PPMS), and 239.88 ng/ml (SD = 46.90) for secondary progressive MS (SPMS).