MTHFR and migraine disorder: Roecklein et al. [17] performed a haplotype analysis of migraine risk and MTHFR, MTRR and methionine synthase (MTR), including subjects with non-migraine headache (N = 367), migraine without aura (N = 85), migraine with aura (N = 167), and no headache (N = 1347).