Unmyelinated nerve fiber degeneration in chronic inflammatory demyelinating polyneuropathy

To determine whether unmyelinated nerve fibers escape degeneration as one m ight expect in an immune response exclusively directed at myelin, we perfor med a morphometric examination of unmyelinated axons and myelinated nerve f ibers in sural nerve biopsy specimens of 14 patients with a chronic inflamm atory demyelinating polyneuropathy (CIDP) and of 12 age-matched normal cont rols. The numbers of unmyelinated axons, myelinated nerve fibers, denervate d Schwann cell units and collagen pockets were quantified and related to th e clinical and electrophysiological data of the patients with CIDP. In 4 pa tients with a rapid onset of the neuropathy and a highly elevated CSF prote in, the numbers of both unmyelinated axons and myelinated nerve fibers were decreased equally. In 8 patients we found that the unmyelinated axons were relatively spared compared with the loss of myelinated nerve fibers. In th ese patients, however, the presence of denervated Schwann cell units and of collagen pockets was increased. We conclude that unmyelinated nerve fibers are affected in patients with CIDP.