The association between EPVS and migraine chronification Our results disproved the initial hypothesis that EPVS might be associated with the migraine chronification. According to previous studies, we believed that the relationship between the severity of EPVS and migraine chronification was bidirectional. Higher grades of EPVS may imply more impairment of the glymphatic system, which may lead to more severe headaches and more frequent attacks, leading to migraine progression.