title: Cortical evoked potentials in response to rapid balloon distension of the rectum and anal canal.
abstract: BACKGROUND
  Neurophysiological evaluation of anorectal sensory function is hampered by a paucity of methods. Rapid balloon distension (RBD) has been introduced to describe the cerebral response to rectal distension, but it has not successfully been applied to the anal canal.
  
  
  METHODS
  Nineteen healthy women received 30 RBDs in the rectum and the anal canal at intensities corresponding to sensory and unpleasantness thresholds, and response was recorded as cortical evoked potentials (CEPs) in 64-channels. The anal canal stimulations at unpleasantness level were repeated after 4 min to test the within-day reproducibility. CEPs were averaged, and to overcome latency variation related to jitter the spectral content of single sweeps was also computed.
  
  
  RESULTS
  Repeated stimulation of the anal canal generated CEPs with similar latencies but smaller amplitudes compared to those from the rectum. Due to latency jitter, reproducibility of averaged CEPs was lower than what was found in the rectum. The most reproducible feature was N2P2 peak-to-peak amplitude with intra-class correlation coefficient (ICC) of 0.7 and coefficient of variation (CV) of 18%. Spectral content of the single sweeps showed reproducibility with ICCs for all bands >0.8 and corresponding CVs <7%.
  
  
  CONCLUSIONS
  Cortical potentials evoked from the anal canal are challenged by latency jitter likely related to variability in muscle tone due to the distensions. Using single-sweep analysis, anal CEPs proved to be reproducible and should be used in future evaluation of the anal function.
authors.affiliation: Department of Surgery, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Haas
authors.forename: C
authors.initials: C
authors.lastname: Brock
authors.forename: K
authors.initials: K
authors.lastname: Krogh
authors.forename: M
authors.initials: M
authors.lastname: Gram
authors.forename: T D
authors.initials: TD
authors.lastname: Nissen
authors.forename: L
authors.initials: L
authors.lastname: Lundby
authors.forename: S
authors.initials: S
authors.lastname: Laurberg
authors.forename: A M
authors.initials: AM
authors.lastname: Drewes
mesh_terms: D000328:Adult; D000368:Aged; D001003:Anal Canal / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D004108:Dilatation, Pathologic / Q000503:physiopathology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D012007:Rectum / Q000502:physiology*
keywords: anal canal; electroencephalography; evoked brain potentials; pain; rectum; unpleasantness