In fact, age-discordant CSF proteins (i.e., decreased in healthy aging and increased in MS aging; Fig. 2a) point towards re-expression of CNS developmental pathways related to axon guidance, EPHB2, EPHB4, EPHB6, NTN1, NOTCH1, NOTCH3, and SHH, which likely mediate CNS repair, as these proteins and their signaling pathways negatively correlate with MS severity. Here, SHH is linked to myeloid sarcoma.