Neurophysiologic studies of POEMS syndrome and its related diseases

Objective To explore the electrophysiological characteristics of polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin changes (POEMS) syndrome and its related diseases. Methods The electrophysiological characteristics were analyzed retrospectively from June 2000 to June 2013 in patients with POEMS syndrome, monoclonal gammopathy of undetermined significance (MGUS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Electromyography and nerve conduction examinations of median, ulnar, tibial, peroneal and sural nerves were performed. Results In patients with POEMS syndrome, the amplitude of compound muscle action potential (CMAP) of tibial and peroneal nerves was lower than that of median and ulnar nerves ((1.02±0.23) vs (2.12±0.30) mV, (P<0.05)); compared with patients with CIDP, the amplitude of CMAP for POEMS patients was lower ((2.12±0.30) vs (3.94±0.52) mV, (1.02±0.23) vs (3.65±0.57) mV)(P<0.05) while terminal latency indices (TLI) was higher ((0.41±0.13) vs (0.22±0.01), (0.45±0.16) vs(0.24±0.13)) (P<0.05) and the occurring rate of conduction block (CB) and temporal dispersion (TD) was lower (P<0.05). Compared with MGUS patients, the amplitude of CMAP for POEMS patients was lower ((2.12±0.30) vs (3.81±0.83) mV, (1.02±0.23) vs (3.82±0.63) mV)(P<0.05); sensory conduction velocity of POEMS patients was faster ((33±5) vs (20±3) m/s, (28±4) vs (18±3) m/s)(P<0.05)). Conclusion Nerve conduction studies of POEMS syndrome implicate both axonal loss and demyelination.Uniform demyelination is more predominant in nerve trunk rather than distal nerve terminals.CB and TD occur less frequently and axonal loss is length-dependent. Key words: POEMS syndrome; Polyradiculoneuropathy, chronic inflammatory demyelinating; Monoclonal gammopathy of undetermined significance; Electromyography