[Chronic inflammatory demyelinating polyneuropathy--an electrophysiological and histological study of the ulnar nerve from a case with intractable persistent conduction block].

We report a 71-year-old male with CIDP, in whom complete motor conduction block persisted for more than several years. Corticosteroid and plasma therapy showed little effect to his weakness. He died of pneumonia. The ulnar nerve in which complete conduction block had persisted was taken out immediately after death and studied with conventional histological and morphometrical techniques. In the transverse section, many thinly-myelinated fibers and some cluster formations were confirmed. Active axonal degeneration was scarce. Myelinated fiber density was 7,417/sgmm. Fiber diameter histogram showed a two-peaked normal distribution. It is thus concluded that demyelination with little axonal degeneration can be the main pathological process causing intractable weakness and poor prognosis of CIDP. Low CMAPs should not lead to therapeutic nihilism, because it may simply be caused by demyelination without exonal degeneration in CIDP.