title: Effect of mexiletine on transitory depression of compound motor action potential in recessive myotonia congenita.
abstract: OBJECTIVE
  We aim to demonstrate the effect of mexiletine on the compound muscle action potential (CMAP) amplitude transitory depression (TD) in a cohort of patients with recessive myotonia congenita.
  
  
  METHODS
  We evaluated 21 patients with recessive myotonia congenita referred to our institute from 1990 to 2013 and treated with mexiletine chlorhydrate. All patients underwent prolonged 3 Hz repetitive nerve stimulation (3 Hz-PLRS) before and after the beginning of treatment.
  
  
  RESULTS
  We observed in all subjects a reduction of CMAP amplitude TD after the beginning of treatment. The mean value of the TD nadir before starting mexiletine treatment was -62.0% and reduced to -28.8% after the therapy was started (51.6% reduction, p<0.001).
  
  
  CONCLUSIONS
  The 3 Hz-PLRS is configured as a neurophysiological test able to indirectly detect and quantify, through the measurement of TD, the clinical phenomenon of the transitory weakness that occurs in myotonic syndromes due to CLCN1 mutations.
  
  
  CONCLUSIONS
  This neurophysiological test might be considered a helpful tool to assess the effect of anti-myotonic drugs, as mexiletine, in recessive myotonia congenita.
authors: Department of Geriatrics, Neurosciences & Orthopedics, Institute of Neurology, Catholic University of the Sacred Heart, Rome, Italy.
authors: Mauro
authors: M
authors: Lo Monaco
authors: Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Hospital, Rome, Italy.
authors: Adele
authors: A
authors: D'Amico
authors: Department of Geriatrics, Neurosciences & Orthopedics, Institute of Neurology, Catholic University of the Sacred Heart, Rome, Italy.
authors: Marco
authors: M
authors: Luigetti
authors: Section of Pharmacology, Department of Pharmacy & Drug Sciences, University of Bari - Aldo Moro, Bari, Italy.
authors: Jean-François
authors: JF
authors: Desaphy
authors: Department of Geriatrics, Neurosciences & Orthopedics, Institute of Neurology, Catholic University of the Sacred Heart, Rome, Italy. Electronic address: amodoni@rm.unicatt.it.
authors: Anna
authors: A
authors: Modoni
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D019054:Evoked Potentials, Motor / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008801:Mexiletine / Q000494:pharmacology* / Q000627:therapeutic use*; D008875:Middle Aged; D009224:Myotonia Congenita / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology*; D013997:Time Factors; D016896:Treatment Outcome; D061567:Voltage-Gated Sodium Channel Blockers / Q000494:pharmacology / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D061567:Voltage-Gated Sodium Channel Blockers; D008801:Mexiletine
keywords: Low-rate repetitive nerve stimulation; Mexiletine; Myotonia; Neurophysiology; Recessive myotonia; Therapy