In our study, the mean AK of the SCC was significantly lower in PD‐nICBs than in PD‐ICBs and HCs, indicating chronic axonal damage (Fig. 4E, blue dotted arrows), and MVF of the ILF was significantly lower, indicating demyelination (Fig. 4E, green dotted arrows).45 This evidence concerns the gene FOXK2 and Parkinson disease.