title: The P18 component of the median nerve SEP recorded from a posterior to anterior neck montage.
abstract: OBJECTIVE
  To investigate the P18 component in the posterior to anterior neck montage after median nerve stimulation.
  
  
  METHODS
  Somatosensory evoked potentials, through electrical wrist stimulation, were collected. In 12 subjects, the presence of the P18 component was evaluated in the posterior to anterior neck montage. In 10 subjects, the effects of simultaneous vibration of the hand were evaluated. In five subjects, responses after double-pulse stimulation (ISI 20 ms) were evaluated.
  
  
  RESULTS
  The P18 component was identified in all subjects. Vibration reduced the amplitude of all components except the P18 and N18. Double-pulse stimulation reduced the amplitude of the P18 and the N18 components without significantly changing the amplitude of the other components.
  
  
  CONCLUSIONS
  The posterior to anterior neck montage allows for recording the P18 component. The amplitude reduction of all components during vibration, except N18 and P18, is interpreted as reflecting inhibitory activities at the cuneiform nucleus and at the segmental dorsal horn of the spinal cord, respectively. The reduction in the P18 component after double-pulse stimulation is compatible with previous observations on the positive component of cord dorsum potentials.
  
  
  CONCLUSIONS
  Studying this component may add to the knowledge of the function of the spinal cord in humans.
authors.affiliation: Department of Neurology and Neurosurgery, Federal University of São Paulo, São Paulo, SP, Brazil.
authors.forename: L M P
authors.initials: LM
authors.lastname: Giuliano
authors.forename: K F
authors.initials: KF
authors.lastname: Nunes
authors.forename: G M
authors.initials: GM
authors.lastname: Manzano
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D008875:Middle Aged; D011930:Reaction Time / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology