Axonal regeneration in the foot branch of the superficial peroneal nerve and the lateral plantar nerve of the rat after sciatic nerve lesions

Hand injuries with nerve lesions often leave the patient with a persistent sensory deficit, particularly with respect to glabrous skin. The present study examines axonal regeneration in the foot branch of the superficial peroneal nerve (fSPN) and the lateral plantar nerve (LPN), supplying hairy skin and glabrous skin together with some intrinsic muscles, respectively, after sciatic nerve lesions in the rat. Following crush lesions, the number of myelinated axons is normal in the fSPN, and the occurrence of C-fibers appears slightly reduced. In the LPN, the numbers of myelinated axons and C-fibers are both significantly increased. Post-crush regenerated myelinated fSPN and LPN axons show normal size ranges, but the proportion of small myelinated axons is increased. After neurotomy and suture, the numbers of myelinated axons and C-fibers in the fSPN are not significantly different from normal. The LPN exhibits a significantly increased number of myelinated axons, but the number of C-fibers is not significantly abnormal. In both nerves, the myelinated axons present an abnormally narrow size range. These findings show that the quantitative outcome of regeneration in a nerve innervating glabrous skin (and some intrinsic muscles) differs significantly from that of branches to hairy skin of the foot, with respect to myelinated as well as unmyelinated axons. To what extent these differences mirror functional differences awaits elucidation.