title: Origin of surface motor unit potentials in hypothenar motor unit number estimation.
abstract: BACKGROUND
  Far-field potentials (FFPs) from muscles other than the abductor digiti minimi (ADM) may interfere with motor unit number estimation (MUNE) from that muscle.
  
  
  METHODS
  We identified the origin of each surface motor unit potential (SMUP) during hypothenar MUNE using the multiple point stimulation method in 20 control subjects by recording from individual ulnar-innervated muscles with a common proximal reference (pref).
  
  
  RESULTS
  ADM SMUPs comprised 39.0% of the accepted SMUPs, followed by those from the fourth dorsal interosseous muscle (14.0%), the fourth lumbrical muscle (9.2%), and the second and third palmar interosseous muscles (8.8% each). The percentage of ADM SMUPs varied from 18% to 73% of accepted SMUPs among individual subjects. Accepted non-ADM SMUPs were usually much smaller than ADM SMUPs, and many more non-ADM SMUPs were excluded due to their small size.
  
  
  CONCLUSIONS
  A large contribution from non-ADM or non-hypothenar SMUPs obscures the meaning of the MUNE value.
authors: Department of Neurology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 1738605, Japan.
authors: Yasuomi
authors: Y
authors: Kawamura
authors: Masahiro
authors: M
authors: Sonoo
authors: Mana
authors: M
authors: Higashihara
authors: Takashi
authors: T
authors: Chiba
authors: Yuki
authors: Y
authors: Hatanaka
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D004558:Electric Stimulation; D004566:Electrodes; D004576:Electromyography; D005260:Female; D006225:Hand / Q000294:innervation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*
keywords: abductor digiti minimi muscle; interosseous muscles; lumbrical muscles; motor unit number estimation; ulnar nerve