MAG and demyelinating polyneuropathy: Previous electrophysiological and imaging studies in MS have suggested that PNS changes may be attributed to Wallerian degeneration caused by spinal cord lesions (26), peripheral codemyelination of the PNS in MS, which is likely to be caused by immunologic reactions and destruction of molecules such as connexin 32 or myelin-associated glycoproteins (3, 19, 27, 28), or epitope spreading, likely to be seen in a special subgroup of people with MS who go on to develop peripheral demyelinating neuropathy during the long course of MS (2).