Difference of segmentalmotor nerve conduction study between chronic inflammatory demyelinatingpolyradiculoneuropathy and Clarcot-Marie-Tooth type 1

Abstract

：Objective to assess theutility of segmental motor nerve conduction study in differential diagnosis of chronicinflammatory demyelinating polyradiculoneuropathy(CIDP)and Charcot-Marie-Tooth type1(CMT1).Methods A segmental motor nerve conduction study was performed on 16 patients withCIDP and 13 patients with CMT1.Distal motor latency,motor nerve conduction velocity,thechanges of amplitude,area and duration of compound motor action potential overconventional segment were compared between the groups.Results Distal motor latency was(5.6±3.4) ms in CIDP and (9.3±2.1) ms in CMT1(t=5.347 P=0.000),motor nerve conductionvelocity was (31.1±14.3) m/s in CIDP and(22.2±5.8)m/s(t=6.369,P=0.000),M50 of thedecrease in amplitude over conventional segment was 29.7% in CIDP and 4.9% in CMT1(Z=7.141,P=0.000).Distal motor latency was normal in 40.3% (25/62) nerves and motor nerveconduction velocity was normal in 18.1% (26/44)of segments in CIDP,while distal motorlatency and motor nerve conduction velocity were abnormal in all nerves in CMT1.Motornerve conduction block or abnormal temporal dispersion was detected in 29.2% segments inCIDP and 3.0% in CMT1 (x2=20.829,P=0.000).Conclusions The segmental motor nerve conductionstudy can help separate CIDP and CMT1.When motor nerve conduction block or abnormaltemporal dispersion is detected,the motor nerve conduction velocity is distinctly variousin different segments,the diagnosis of CIDP but not CMT1 should be considered.