title: Low-rate repetitive nerve stimulation protocol in an Italian cohort of patients affected by recessive myotonia congenita.
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.
authors.affiliation: Department of Neuroscience, Catholic University, Rome, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Modoni
authors.forename: Adele
authors.initials: A
authors.lastname: D'Amico
authors.forename: Bruno
authors.initials: B
authors.lastname: Dallapiccola
authors.forename: Maria Lucia
authors.initials: ML
authors.lastname: Mereu
authors.forename: Luciano
authors.initials: L
authors.lastname: Merlini
authors.forename: Serena
authors.initials: S
authors.lastname: Pagliarani
authors.forename: Elisa
authors.initials: E
authors.lastname: Pisaneschi
authors.forename: Gabriella
authors.initials: G
authors.lastname: Silvestri
authors.forename: Isabella
authors.initials: I
authors.lastname: Torrente
authors.forename: Enza Maria
authors.initials: EM
authors.lastname: Valente
authors.forename: Mauro
authors.initials: M
authors.lastname: Lo Monaco
mesh_terms: D000200:Action Potentials / Q000235:genetics / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000368:Aged; D018118:Chloride Channels / Q000235:genetics; D015331:Cohort Studies; D004558:Electric Stimulation / Q000379:methods*; D004576:Electromyography; D005192:Family Health; D005260:Female; D056726:Genetic Association Studies; D005820:Genetic Testing; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D009224:Myotonia Congenita / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology*; D062553:NAV1.4 Voltage-Gated Sodium Channel; D009431:Neural Conduction / Q000235:genetics / Q000502:physiology*; D009460:Neurologic Examination; D015222:Sodium Channels / Q000235:genetics; D014459:Ulnar Nerve / Q000503:physiopathology*; D055815:Young Adult
chemical_list: C086321:CLC-1 channel; D018118:Chloride Channels; D062553:NAV1.4 Voltage-Gated Sodium Channel; C106251:SCN4A protein, human; D015222:Sodium Channels