title: Fibular motor nerve conduction studies: Investigating the mechanism for compound muscle action potential amplitude drop with proximal stimulation.
abstract: BACKGROUND
  The compound muscle action potential (CMAP) amplitude of extensor digitorum brevis can show a drop with proximal stimulation in normal fibular nerves.
  
  
  METHODS
  We assessed the contribution of the far-field potential recorded by the reference electrode (R-CMAP) to the fibular CMAP. Negative R-CMAP amplitude, peak-to-peak amplitude, and negative area were measured and correlated with the amplitude decrease. Fibular motor nerves from 14 healthy participants were studied.
  
  
  RESULTS
  The mean CMAP amplitude drop with proximal stimulation was 14.0 ± 9.3%, including a >30% reduction in 1 study. All measured R-CMAP parameters correlated with the degree of amplitude drop.
  
  
  CONCLUSIONS
  A greater R-CMAP contribution to the fibular CMAP leads to greater phase cancellation and temporal dispersion. The resulting amplitude drop seen in the proximal CMAP can be large enough to be classified incorrectly as "probable conduction block" by several different diagnostic criteria.
authors.affiliation: Department of Neurology & Neurological Research, St. Vincent's Hospital Melbourne, P.O. Box 2900, Fitzroy, 3065, Melbourne, Victoria, Australia.
authors.forename: Jordan T
authors.initials: JT
authors.lastname: Kamel
authors.affiliation: Department of Neurology & Neurological Research, St. Vincent's Hospital Melbourne, P.O. Box 2900, Fitzroy, 3065, Melbourne, Victoria, Australia.
authors.forename: Rory J
authors.initials: RJ
authors.lastname: Knight-Sadler
authors.affiliation: Department of Neurology & Neurological Research, St. Vincent's Hospital Melbourne, P.O. Box 2900, Fitzroy, 3065, Melbourne, Victoria, Australia.
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Roberts
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D001703:Biophysics; D004558:Electric Stimulation; D004566:Electrodes; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology*; D010543:Peroneal Nerve / Q000502:physiology*; D055815:Young Adult
keywords: CMAP; amplitude drop; conduction block; fibular nerve; nerve conduction studies