Comparison of Nerve Conduction Studies between the Patients with Hereditary Neuropathy with Liability to Pressure Palsies and Charcot-Marie-Tooth1A

ABSTRACT

BACKGROUND: Hereditary neuropathy with liability to pressure palsy (HNPP) and Charcot-Marie-Tooth1A (CMT1A) are autosomal dominant inherited demyelinating neuropathy associated with the deletion or duplication of 17p11.2-p12 segments including the gene for peripheral myelin protein 22 (PMP22). The aim of this study is to compare the electrophysiological features of these two disorders genetically related. METHODS: We studied the nerve conduction studies of genetically confirmed 43 HNPP in 23 families and 31 CMT1A patients in 13 families. RESULTS: Nerve conduction studies presented prolonged terminal latency, slow nerve conduction velocity and low amplitude of compound muscle or nerve action potentials in both diseases, but more severe in CMT1A. The incidence of conduction block with or without dispersion was higher in CMT1A than HNPP, with 23.6% and 5.7% respectively. CMT1A revealed a rather even distribution of abnormalities in segmental nerve conduction studies than HNPP. HNPP showed frequent involvements at the segment of entrapment-prone site such as peroneal and ulnar nerves. The characteristical differences of these diseases could be defined by the quantitative correlation study. The correlation coefficients of nerve conduction velocities between tested nerves in the same or different limbs and between tested segments of the same nerve was much higher in CMT1A than HNPP. CONCLUSIONS: We conclude that CMT1A presents with more severe diffuse and uniform slowing, whereas HNPP presents with focal electrophysiological abnormalities.