Referenced in: none

Automatically associated channels: ClC1 , ClC4 , Nav1.4

Title: Low-rate repetitive nerve stimulation protocol in an Italian cohort of patients affected by recessive myotonia congenita.

Authors: Anna Modoni, Adele D'Amico, Bruno Dallapiccola, Maria Lucia Mereu, Luciano Merlini, Serena Pagliarani, Elisa Pisaneschi, Gabriella Silvestri, Isabella Torrente, Enza Maria Valente, Mauro Lo Monaco

Journal, date & volume: J Clin Neurophysiol, 2011 Feb , 28, 39-44

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/21221019

Abstract
Transitory depression of the compound muscle action potential during repetitive nerve stimulation is a well-documented neurophysiologic finding in recessive myotonia congenita. It represents the neurophysiologic counterpart of the transitory weakness often impairing patients at the beginning of a movement after rest, and it is usually better induced using high-rate nerve stimulations. The authors examined 30 patients with recessive myotonia congenita and carried out a 3 Hz nerve stimulation study to ascertain to what extent this protocol was able to detect the occurrence of transitory depression. Their findings were compared with the results obtained by 12 patients affected by dominant myotonia congenita and 12 patients affected by nondystrophic myotonia due to SCN4A mutations. Molecular genetic analysis of the CLCN1 and SCN4A genes was also performed. The 3 Hz nerve stimulation protocol was well tolerated and showed high sensitivity, resulting positive in 66% of recessive case and good reproducibility, if performed after an adequate period of rest. All dominant cases and all patients affected by myotonia due to SCN4A mutations showed negative results. Molecular studies identified 26 different CLCN1 mutations, 16 of which were novel. Transitory depression confirmed to vary in accordance to CLCN1 mutations. The 3 Hz protocol was well tolerated and showed good sensitivity and reproducibility. Furthermore, this test might be suitable for genotype-phenotype correlation studies.