The electrophysiological characteristics of the four most common genotypes of Charcot-Marie-Tooth disease / 中华神经科杂志

ABSTRACT

Objective To analyze the electrophysiological characteristics of Charcot-Marie-Tooth (CMT) disease 1A,1X,2A and myelin protein zero (MPZ)-related CMT in Chinese patients.Methods Baseline electrophysiological data from 36 CMT1A patients,78 CMT1X patients,31 CMT2A patients and 10 MPZ-related CMT patients in the Third Xiangya Hospital and Xiangya Hospital of Central South University during 2004-2018 were analyzed.Electrophysiological recordings were taken from the upper limbs (median nerve,ulnar nerve) and lower limbs (tibial nerve,peroneal nerve).Demyelination in different nerve segments was assessed by measurement of distal motor latency,motor nerve conduction velocity (MNCV),sensory nerve conduction velocity and F-wave latency,and calculation of conduction block,terminal latency index (TLI) and modified F ratio (MFR);Axonal degeneration was assessed by measuring compound motor action potential (CMAP) and sensory nerve action potential.The relationship between the gender,age at onset,duration,Overall Neuropathy Limitation Scale (ONLS) score and indexes of peripheral nerve electrophysiology was statistically analyzed.Results The peripheral nerves of CMT1A patients were characterized by uniform demyelination and axonal degeneration.MNCV ((21.39± 6.72) m/s) and CMAP amplitude (2.40 (3.50) mY) of median nerve of CMT1A patients were decreased.The peripheral nerves of CMT1X patients were also characterized by uniform demyelination and axonal degeneration.MNCV (35.20 (6.77) m/s) and CMAP amplitude (2.60 (3.79) mY) of median nerve of CMT1X patients were decreased.CMT2A patients showed axonal degeneration of the peripheral nerves and CMAP amplitude ((4.75 ±2.38) mV) of median nerve of CMT2A patients was decreased.The electrophysiological data in MPZ-related CMT patients demonstrated variability.The TLI and MFR for the median and ulnar nerves in these four subtypes were normal.MNCV (r=0.423,P=0.025) of median nerve in CMT1A patients was positively correlated with age at onset.MNCV (r=0.782,P=-0.013) of median nerve in MPZ-related CMT patients was positively correlated with age at onset.CMAP amplitude (r=0.652,P＜0.01) of median nerve in CMT2A patients was positively correlated with age at onset.Demyelination and axonal degeneration in male CMT1X patients were relatively more severe than those in female patients,and MNCV (Z=-3.300,P＜0.01) and CMAP amplitude (Z=-3.960,P＜0.01) of median nerve,MNCV (Z=-2.56,P=0.011) and CMAP amplitude (Z=-2.311,P=0.048) of ulnar nerve of male patients were lower than those of female patients.The ONLS score of CMT1A (r=-0.494,P＜0.01),CMT1X (r=-0.596,P＜0.01) and CMT2A patients (r=-0.494,P=0.012) was inversely associated with CMAP amplitude.Conclusions The electrophysiological characteristics of CMT1A,CMT1X,CMT2A and MPZ-related CMT are different.Electrophysiological examinations are the basis of clinical classification and could provide guidance for further genetic testing and diagnosis.CMAP amplitude may serve as an objective index to assess the severity of functional disability in CMT patients.