Electrophysiological Characteristics in Patients of Charcot-Marie-Tooth type 2A

J Korean Assoc EMG Electrodiagn Med 2006;8(2):75-84.
Published online May 10, 2006.

Abstract

Objectives: The aim of this study is to identify the electrophysiological characteristics in CMT2A patients with the MFN2 mutations. Methods: We examined mutations of MFN2 gene in 165 Korean CMT families. By criteria from European CMT consortium, 54 families belonged to CMT2. Mutations were confirmed by both strands sequencing. We administrated the CMT neuropathy score (CMTNS), based on patient’s symptoms, neurological examination and neurophysiological testing, and the functional disability scale (FDS) for evaluation of disease severity. Muscular strength was assessed manually with the standard MRC. Results: The electrophysiological patterns associated with MFN2 mutations were typical of axonal CMT. The electrophysiological data were markedly different between early onset (<10 years) and late onset (≥ 10 years) groups. All patients with early onset have a severe CMTNS (≥21), and FDS (≥6). However, most patients with late onset have a mild CMTNS (≤10), and FDS (≤3). Distal muscle strength, CMTNS, and FDS were well correlated with CMAPs of all motor nerves. No correlation was found between the degree of slowing of MNCV of median and ulnar nerves, and the degree of CMAP attenuation. Conclusions: Electrophysiological features in patients with MFN2 mutations were significantly different between early onset and late onset groups, and CMTNS is a valuable measure of length-dependent axonal CMT2A.

Key Words: Charcot-Marie-Tooth disease, CMT2A, Mitofusin 2 (MFN2), Electrophysiology