title: Modulation of intracortical inhibition in response to acute psychosocial stress is impaired among individuals with chronic neck pain.
abstract: OBJECTIVE
  Psychosocial stress has been associated with a variety of chronic pain disorders although the mechanisms responsible for this relationship are unknown. The purpose of this study was to compare the excitability of intracortical and corticospinal pathways to the trapezius muscle in individuals with and without chronic neck pain during exposure to low and high levels of psychosocial stress.
  
  
  METHODS
  Single and paired-pulse transcranial magnetic stimulation was used to assess motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) during mental math performed in the presence and absence of social evaluative threat.
  
  
  RESULTS
  All participants demonstrated higher amplitude MEPs in the high stress compared to the low stress condition (p < 0.01). Participants with chronic neck pain had significantly greater SICI than healthy participants in the low stress condition (p = 0.03). During exposure to the stressor, healthy participants showed an increase in SICI, whereas participants with neck pain showed no change (group difference for change in SICI, p < 0.01).
  
  
  CONCLUSIONS
  These findings suggest that individuals with chronic neck pain inhibit motor output to the trapezius in the presence of minor stressors, and are unable to compensate for additional stress-evoked increases in corticospinal excitability through further modulation of SICI. This observation has potential implications for the management of patients who have difficulty relaxing painful muscles during times of stress.
authors: Rehabilitation Science Program, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
authors: Ryan J
authors: RJ
authors: Marker
authors: Clinical Science Program, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
authors: Jennifer L
authors: JL
authors: Stephenson
authors: Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
authors: Benzi M
authors: BM
authors: Kluger
authors: Division of Biostatistics and Bioinformatics, National Jewish Health, Denver, CO, USA; Department of Biostatistics and Informatics, Colorado School of Public Health, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
authors: Douglas
authors: D
authors: Curran-Everett
authors: Rehabilitation Science Program, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; Physical Therapy Program, University of Colorado Anschutz Medical Campus, Aurora, CO, USA. Electronic address: Katrina.Maluf@ucdenver.edu.
authors: Katrina S
authors: KS
authors: Maluf
mesh_terms: D000328:Adult; D059350:Chronic Pain / Q000503:physiopathology*; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D019547:Neck Pain / Q000503:physiopathology*; D009433:Neural Inhibition; D011712:Pyramidal Tracts / Q000503:physiopathology*; D013315:Stress, Psychological / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation
keywords: Anxiety; Electromyography; Motor cortex; Motor evoked potential; Transcranial magnetic stimulation; Trapezius muscle