title: Differences in spinothalamic function of cervical and thoracic dermatomes: insights using contact heat evoked potentials.
abstract: BACKGROUND
  After spinal cord injury, contact heat evoked potentials (CHEPs) may represent a means to refine the clinical assessment of sensory function from each spinal cord segment by quantifying nociception, including conduction along the spinothalamic tract.
  
  
  METHODS
  The influence of stimulation site (i.e., dermatomes) on CHEPs and thermal thresholds in 19 healthy subjects (mean age, 45.2 ± 18.3 years) divided into 2 age classes (younger subjects, n = 10; mean age, 28.8 ± 5.2 years; older subjects, n = 9; mean age, 63.4 ± 3.4 years) at 5 different dermatomes (C4, C5, C6, C8, and T4) was assessed.
  
  
  RESULTS
  In terms of distance from the body midline (i.e., spinal cord entry), there was a reduction in CHEP amplitudes from proximal (C4 and T4) to distal (C6 and C8) dermatomes with a corresponding reduction in nociceptive perception (i.e., pain threshold and rating). Within primary and secondary cortical sensory areas, including areas associated with affective noxious processing, the cortical source density analysis showed a similar current density distribution between C4 and C8 dermatomes but consistent higher current densities for C4.
  
  
  CONCLUSIONS
  The study supports CHEPs as a feasible tool for assessing discrete dermatomes corresponding to spinal cord segments. The results suggest that the proximodistal pattern in the intensity of perceived pain and CHEP amplitudes is likely attributable to the distribution of heat nociceptors and the increase in conduction distance from proximal to distal dermatomes. The present findings emphasize on the importance that if patients are assessed segment by segment, the underlying topographical differences need to be accounted for.
authors.affiliation: Spinal Cord Injury Center, University Hospital Balgrist, Zurich, Switzerland. jhaefeli@paralab.balgrist.ch
authors.forename: Jenny S
authors.initials: JS
authors.lastname: Haefeli
authors.forename: Julia
authors.initials: J
authors.lastname: Blum
authors.forename: John D
authors.initials: JD
authors.lastname: Steeves
authors.forename: John L K
authors.initials: JL
authors.lastname: Kramer
authors.forename: Armin E P
authors.initials: AE
authors.lastname: Curt
mesh_terms: D000328:Adult; D000368:Aged; D004569:Electroencephalography / Q000379:methods; D005071:Evoked Potentials; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D058748:Pain Perception / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012867:Skin / Q000294:innervation* / Q000503:physiopathology*; D013127:Spinal Nerves / Q000502:physiology*; D055815:Young Adult