title: Clarifying distal axonal properties of the median nerve.
abstract: BACKGROUND
  Although length-dependent axonal excitability changes have been reported in the median nerve, the mechanisms underlying these changes remain to be further clarified.
  
  
  METHODS
  Axonal excitability studies were performed on median nerve at the palm and wrist in 20 healthy controls, with responses recorded over the abductor pollicis brevis.
  
  
  RESULTS
  The strength-duration time constant was significantly shorter (palm: 0.35 ± 0.01 ms; wrist: 0.48 ± 0.03 ms; P < 0.001), whereas rheobase was significantly increased (palm: 2.90 ± 1.12 mA; wrist: 2.09 ± 1.11 mA; P < 0.05) at the palm. In addition, there was a significant increase in depolarizing threshold electrotonus at 90-100 ms (P < 0.001) and a reduction in S2 accommodation (P < 0.001) and late subexcitability (P < 0.001) at the palm. The changes in excitability were independent of factors influencing median nerve cross-sectional area.
  
  
  CONCLUSIONS
  The present study reveals significant length dependent changes in median nerve excitability which may reflect differences in intrinsic membrane properties.
authors.affiliation: Sydney Medical School Westmead, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Dominic
authors.initials: D
authors.lastname: Moore
authors.forename: Parvathi
authors.initials: P
authors.lastname: Menon
authors.forename: Steve
authors.initials: S
authors.lastname: Vucic
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D019412:Anatomy, Cross-Sectional; D001369:Axons / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006225:Hand / Q000294:innervation; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000166:cytology* / Q000502:physiology*; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation; D009431:Neural Conduction; D015221:Potassium Channels / Q000502:physiology; D014953:Wrist / Q000294:innervation; D055815:Young Adult
chemical_list: D015221:Potassium Channels