title: Significant CMAP decrement by repetitive nerve stimulation is more frequent in median than ulnar nerves of patients with amyotrophic lateral sclerosis.
abstract: BACKGROUND
  Several studies have shown a significant amplitude decrement in compound muscle action potentials (CMAPs) on repetitive nerve stimulation (RNS) of muscles involved in amyotrophic lateral sclerosis (ALS). In ALS, muscle wasting preferentially affects the thenar muscles (APB) rather than the hypothenar muscles (ADM).
  
  
  METHODS
  We performed RNS studies in the APB and ADM muscles of 32 ALS patients to determine whether the effect of RNS differs between the median and ulnar nerves.
  
  
  RESULTS
  The decremental responses to RNS were greater in the APB than in the ADM. Reduced CMAP amplitude was negatively correlated with CMAP decrement in median but not in ulnar nerves.
  
  
  CONCLUSIONS
  The greater CMAP decrement in median nerve is attributable to preferential involvement of the APB in the pathophysiology of ALS or some underlying difference in the biology of the two muscles/nerves. Further investigations will better our understanding of the pathophysiology of ALS.
authors.affiliation: Department of Neurology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan. y-stsh@kumamoto-u.ac.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamashita
authors.forename: Hideya
authors.initials: H
authors.lastname: Sakaguchi
authors.forename: Akira
authors.initials: A
authors.lastname: Mori
authors.forename: En
authors.initials: E
authors.lastname: Kimura
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Maeda
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Hirano
authors.forename: Makoto
authors.initials: M
authors.lastname: Uchino
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000473:pathology*; D055592:Biophysical Phenomena / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D012189:Retrospective Studies; D014459:Ulnar Nerve / Q000503:physiopathology*; D055815:Young Adult