title: Conditioned Pain Modulation in Patients With Acute and Chronic Low Back Pain.
abstract: OBJECTIVE
  Disturbed endogenous pain modulation is likely one of the mechanisms underlying central hypersensitivity and might be a contributing factor for the development and maintenance of chronic pain. To our knowledge, no study has investigated endogenous pain modulation in both acute and chronic low back pain (LBP). We tested the hypothesis that endogenous pain inhibition is impaired in patients with acute and chronic LBP.
  
  
  METHODS
  We evaluated 40 patients with acute LBP, 34 patients with chronic LBP and 30 pain-free controls for their conditioned pain modulation (CPM), with pressure pain tolerance and cold pressor as test and conditioning stimulus, respectively. Measurements were repeated up to 10 minutes after cold pressor test.
  
  
  RESULTS
  There was no difference in CPM among the groups immediately after cold pressor test. However, the decline in CPM effect was significantly faster in chronic and acute LBP patients than in controls, with no evidence for differences between pain groups.
  
  
  CONCLUSIONS
  The present study provides evidence for some alterations of endogenous modulation in both acute and chronic LBP. CPM was still detected in both patient groups, indicating that endogenous modulation, although effective for a shorter duration, is partially functioning in patients with LBP.
authors.affiliation: *Department of Anesthesiology and Pain Therapy, Inselspital-University Hospital of Bern‡CTU Bern, Department of Clinical Research, and Institute of Social and Preventive Medicine (ISPM), University of Bern, Bern†Department of Obstetrics and Gynaecology, Cantonal Hospital of Winterthur, Winterthur, Switzerland§Department of Health Science and Technology, Center for Sensory-Motor Interaction, University of Aalborg, Aalborg, Denmark∥Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA.
authors.forename: Sabine
authors.initials: S
authors.lastname: Mlekusch
authors.forename: Alban Y
authors.initials: AY
authors.lastname: Neziri
authors.forename: Andreas
authors.initials: A
authors.lastname: Limacher
authors.forename: Peter
authors.initials: P
authors.lastname: Jüni
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.forename: Michele
authors.initials: M
authors.lastname: Curatolo
mesh_terms: D059787:Acute Pain / Q000503:physiopathology*; D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D059350:Chronic Pain / Q000503:physiopathology*; D003080:Cold Temperature; D005260:Female; D007839:Functional Laterality; D006801:Humans; D006930:Hyperalgesia / Q000503:physiopathology*; D017116:Low Back Pain / Q000503:physiopathology* / Q000523:psychology; D008297:Male; D008875:Middle Aged; D018710:Pain Clinics; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D011312:Pressure; D013997:Time Factors