title: Temporal summation of pain evoked by mechanical stimulation in deep and superficial tissue.
abstract: Temporal summation of deep tissue pain has been suggested to be facilitated in chronic musculoskeletal pain syndromes. This study aimed to test whether temporal summation of mechanical induced pressure pain is (1) more pronounced at short (1 second) interstimulus intervals (ISIs) compared with long ISI (30 seconds), (2) more potent than summation elicited by pure skin stimulation, and (3) attenuated in women compared with men. Twelve age-matched men and 12 women were included. A computer-controlled pressure stimulator with a probe surface of 1 cm2 was used to give 10 stimulations to the tibialis anterior, tibia periosteum, and the first web of the hand. Sequential stimulation at pressure pain threshold intensity was applied with different ISIs (1, 3, 5, 10, and 30 seconds). The pain intensity was assessed on a visual analog scale (VAS) after each individual stimulus. The VAS scores after the 10th stimulation with 1-second ISI were increased (P < .05) by 418% +/- 77%, 378% +/- 89%, and 234% +/- 66% compared with the first stimulation for tibia, tibialis anterior, and web, respectively. Temporal summation of pain was observed for all ISIs in tibialis anterior and tibia, eg, 30-second ISI evoked a VAS increase of 192% +/- 71 % (tibia) and 117% +/- 42% (tibialis anterior) compared with the first stimulation. The VAS score after the 10th web stimulation was smaller (P < .05) than that of the 10th tibialis anterior or tibia stimulation. A regression analysis between stimulation number and VAS score showed that the pain intensity increased progressively (1) more for 1-second ISIs compared with longer ISIs (P < .01) and (2) faster in deep tissue compared with skin (P < .01). No gender difference was observed. The temporal summation might be related to both central and peripheral mechanisms.
  
  
  CONCLUSIONS
  Pain originating in deep tissue influences central pain processing systems more than superficial tissue. This might be of importance in patients with musculoskeletal pain.
authors.affiliation: Laboratory for Experimental Pain Research, Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark.
authors.forename: Hongling
authors.initials: H
authors.lastname: Nie
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.forename: Helle
authors.initials: H
authors.lastname: Andersen
authors.forename: Thomas
authors.initials: T
authors.lastname: Graven-Nielsen
mesh_terms: D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D002490:Central Nervous System / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D009140:Musculoskeletal Diseases / Q000503:physiopathology; D009619:Nociceptors / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D010521:Periosteum / Q000294:innervation / Q000503:physiopathology; D010812:Physical Stimulation / Q000295:instrumentation / Q000379:methods; D012727:Sex Characteristics; D012867:Skin / Q000294:innervation / Q000503:physiopathology; D040521:Subcutaneous Tissue / Q000294:innervation / Q000503:physiopathology; D013997:Time Factors