Polyneuropathy is often an initial manifestation of polyneuropathy, 
organomegaly, endocrinopathy, M protein and skin changes (POEMS) syndrome and 
therefore this disorder is frequently misdiagnosed as chronic inflammatory 
demyelinating polyneuropathy (CIDP). We reviewed electrophysiological data in 20 
patients with POEMS syndrome and 36 matched patients with CIDP to compare the 
electrophysiological features of POEMS syndrome and CIDP. Compared with CIDP 
controls, POEMS patients demonstrated (1) less prolonged distal motor latency 
and less reduced motor nerve and sensory nerve conduction velocities, (2) 
greater reduction of amplitudes of compound motor action potentials (CMAP) in 
distal stimulation, and similar reduction of amplitudes of CMAP in proximal 
stimulation, (3) similar reduction of amplitudes of sensory nerve action 
potentials (SNAP) in median and ulnar nerves, and a greater reduction of 
amplitudes of SNAP in tibial and peroneal nerves, (4) less temporal dispersion, 
(5) less frequent conduction block, (6) more frequent neurogenic injury in the 
muscles of the upper and lower limbs, and more frequent neurogenic injury in the 
muscles of the lower than upper limbs, (7) similar F wave and H reflex 
abnormalities, and (8) less frequent skin sympathetic response abnormalities. We 
concluded that before development of typical clinical manifestations, POEMS 
neuropathy can be distinguished from CIDP by neural electrophysiological 
examination. These electrophysiological features can be used for early diagnosis 
and initiating correct treatment of POEMS syndrome.