Introduction: In the demyelinating form of Charcot-Marie-Tooth disease, median motor conduction velocity (MCV) was noted to be around 20 m/s in peripheral myelin protein 22 (PMP22) duplications, in contrast to higher MCVs in connexin 32 gene (Cx32) mutations and lower MCVs in the demyelinating form of myelin protein zero gene (MPZ) mutations.
Methods: Nerve conduction studies were performed in 64 families with both common and rare mutations.
Results: Mean MCV of the median nerve was 20 ± 5 m/s in PMP22 duplications, 34 ± 6 m/s in Cx32 mutations, 20 ± 9 m/s in KIAA1985 (SH3TC2) mutations, and 11 ± 8 m/s in MPZ mutations. Conduction was generally uniform; however, conduction blocks were present in 1 patient each with the MPZ mutation and PMP22 duplication, both with unusual phenotypes.
Conclusion: Our results confirm those of the other investigators. Electrophysiological results of the rare KIAA1985 (SH3TC2) mutation reveal that their MCVs span a broad range and that conduction is uniform.
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