Peripheral Nerve Axon Involvement in Myotonic Dystrophy Type 1, Measured Using the Automated Nerve Excitability Test

• Published in: Journal of clinical neurology (Seoul, Korea) Vol. 7; no. 2; pp. 90 - 95
• Main Authors: Bae, Jong Seok, Kim, Sang Gin, Lim, Jeong Cheol, Chung, Eun Joo, Kim, Oeung Kyu
• Format: Journal Article
• Language: English
• Published: Korea (South) Korean Neurological Association 01.06.2011; 대한신경과학회
• Subjects: Original; 신경과학; myotonic dystrophy; axonal excitability; neuropathy; nerve excitability test; threshold tracking
• ISSN: 1738-6586; 2005-5013; 2005-5013
• DOI: 10.3988/jcn.2011.7.2.90

Primary involvement of the peripheral nerves in myotonic dystrophy type I (MyD1) is controversial. We investigated whether the involvement of peripheral nerves is a primary event of MyD1 or secondary to another complication such as diabetes mellitus (DM). The subjects comprised 12 patients with MyD1, 12 with DM and no peripheral nerve involvement, and 25 healthy volunteers. We measured multiple excitability indices in the median motor axons. The strength-duration time constant was calculated from the duration-charge curve, the threshold electrotonus and current-threshold relationships were calculated from the sequential subthreshold current, and the recovery cycle was derived from double suprathreshold stimulation. The depolarizing and hyperpolarizing threshold electrotonus were significantly reduced and exhibited increased refractoriness in the MyD1 group compared with the DM and control groups. The SDTC, superexcitability, and subexcitability were not significantly altered in the MyD1 group. The MyD1 group exhibited a depolarized axonal membrane potential. The significant differences in peripheral nerve excitability between the MyD1 group and the DM and normal control groups suggest that peripheral neuropathy is a primary event in MyD1 rather than a secondary complication of DM.