Background: Patients with chronic whiplash associated disorders (WAD) demonstrate altered
central pain processing and impaired endogenous analgesia. In addition, previous research
reported disturbances in the autonomic nervous system and the presence of post-traumatic
stress reaction in patients with chronic WAD. The autonomic nervous system, in particular the
autonomic stress response, might modulate central pain processing in this population.
Objectives: The goal of this study was to compare the autonomic response to acute painful
stimuli in patients with chronic WAD and healthy controls and to look for associations between
endogenous analgesia and autonomic parameters.
Study design: Case-control study.
Methods: Thirty patients with chronic WAD and 31 healthy controls were subjected to an
experiment evaluating the autonomic nervous system at rest and during experimental painful
stimuli. Skin conductance, heart rate, and heart rate variability parameters were monitored
continuously during the evaluation of conditioned pain modulation. The paradigm of heterotopic
noxious conditioning stimulation was used to assess this conditioned pain modulation effect.
Results: The data revealed no difference in autonomic response to pain between chronic WAD
and healthy controls. The autonomic response was unrelated to pressure pain thresholds or the
effect of conditioned pain modulation in either group.
Limitations: The present study only investigates the autonomic response to a stress caused by
pain.
Conclusion: Results of this study refute autonomic dysfunction in response to pain in patients
with chronic WAD. The autonomic nervous system activity or reactivity to acute pain appears
unrelated to either pain thresholds or endogenous analgesia in patients with chronic WAD.
Key words: chronic whiplash associated disorders, central sensitization, pain modulation;
posttraumatic stress disorder ,sympathetic, heart rate variability
Cerebral responses and role of the prefrontal cortex in conditioned pain modulation: an fMRI study in healthy subjects
