title: Correlation between compound muscle action potential amplitude and duration in axonal and demyelinating polyneuropathy.
abstract: OBJECTIVE
  To get a better understanding of pathophysiology in polyneuropathies (PNPs) by correlating compound muscle action potential (CMAP) amplitude with duration.
  
  
  METHODS
  A total of 145 motor nerve conduction studies (MNCS) in 53 axonal and 132 MNCS in 45 demyelinating PNPs were analyzed. Peroneal and tibial MNCS were done by surface stimulation while for median and ulnar nerves near nerve or surface stimulations were used. CMAP amplitude and duration were compared in axonal and demyelination PNPs. Relationships between amplitude and duration of distally and proximally evoked CMAP were examined using regression analysis.
  
  
  RESULTS
  CMAP amplitude was lower and duration was increased in all examined nerves in demyelinating PNPs than in axonal PNPs. In demyelinating PNPs, an inverse linear correlation between amplitude and duration was seen in distally and proximally evoked CMAP in all examined nerves. In axonal PNPs, there was no correlation in any of the nerves neither in distally nor in proximally evoked CMAP.
  
  
  CONCLUSIONS
  Distal CMAP duration and the relationship between CMAP amplitude and duration show supplementary electrodiagnostic potential in demyelinating PNPs.
  
  
  CONCLUSIONS
  More knowledge about the relation between amplitude and duration in axonal lesions and demyelination may help to reveal the pathophysiology in PNPs. Significant correlation between amplitude and duration in demyelination may suggest that the severe decrease in amplitude in demyelinating PNPs is probably due to the increase in duration secondary to temporal dispersion.
authors.affiliation: Department of Clinical Neurophysiology, Aarhus University Hospital, DK - 8000 Aarhus, Denmark.
authors.forename: Hatice
authors.initials: H
authors.lastname: Tankisi
authors.forename: Marit
authors.initials: M
authors.lastname: Otto
authors.forename: Kirsten
authors.initials: K
authors.lastname: Pugdahl
authors.forename: Birger
authors.initials: B
authors.lastname: Johnsen
authors.forename: Anders
authors.initials: A
authors.lastname: Fuglsang-Frederiksen
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D001369:Axons / Q000502:physiology*; D003711:Demyelinating Diseases / Q000503:physiopathology*; D004576:Electromyography; D006801:Humans; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology*; D011115:Polyneuropathies / Q000503:physiopathology*