GAP-43+ IENFD was reduced in patients with CTS before surgery compared to healthy controls with no difference in GAP-43+ IENFD before and after surgery (median [IQR] healthy 3.5 [5.9] fibres/mm epidermis, CTS pre 0.3 [1.5], CTS post 0.6 [1.1], Mann Whitney U p = 0.021, Wilcoxon p = 0.498, Fig 1A). Here, GAP43 is linked to carpal tunnel syndrome.