Electrophysiological features in the distinction between hereditary demyelinating and chronic acquired demyelinating neuropathies

Abstract

We carried out an electrophysiological retrospective study in 55 patients with chronic demyelinating acquired and hereditary neuropathies. Alterations of motor nerve conduction velocities (MNCV), distal motor latencies (DML), conduction blocks (CB) and compound muscle action potential (CMAP) were compared, considering the whole number of nerves for each disease. MNCV, DML, CB and CMAP were considered suggestive of demyelination when meeting the American Academy of Neurology (AAN) criteria. Abnormally slow MNCV was found respectively in the 46% of all the CMTX female nerves studied, in the 56.5% of CMTX males, 84% of CMT1A, 74% CIDP and 70% of MAG‐PNP. Prolonged DML was observed in the 25% of the CMTX female nerves studied, in the 49.5% of CMTX males, 81% of CMT1A, 63% of CIDP and 71% of MAG‐PNP. Moreover, CB were quite often evidenced in CIDP and MAG‐PNP nerves (respectively in 48% and 29%) and rarely in hereditary neuropathies. Finally, we observed CMAP reduction in the 45% of all the CMTX female nerves studied, in the 50% of CMTX males, 63% of CMT1A, 49% of CIDP and 60% of MAG‐PNP. A well‐characterized pattern generally allows an electrophysiological distinction between CMT1A, CMTX males, MAG‐PNP on one side and CIDP and CMTX females on the other side. A clear electrodiagnostic distinction result is often hard between CMTX males and MAG‐PNP and between CIDP and CMTX females.