Central sensitization and altered central pain processing in chronic low back pain: fact or myth?

OBJECTIVE: The purpose of this narrative review is to analyze the available literature concerning central sensitization and altered central pain processing in patients with chronic low back pain (LBP). METHODS: Literature was screened using several electronic search databases. Additional literature was obtained by reference tracking and expert consultation. Studies evaluating central pain processing in conservatively treated patients with chronic LBP were included. RESULTS: Results of studies examining the responsiveness to various stimuli in patients with chronic LBP are conflicting. Some studies in patients with chronic LBP have demonstrated exaggerated pain responses after sensory stimulation of locations outside the painful region, while other studies report no differences between patients and healthy subjects. Studies examining the integrity of the endogenous pain inhibitory systems report unaltered activity of this descending inhibitory system. In contrast, studies analyzing brain structure and function in relation to (experimentally induced) pain provide preliminary evidence for altered central nociceptive processing in patients with chronic LBP. Finally, also psychosocial characteristics, such as inappropriate beliefs about pain, pain catastrophizing, and/or depression may contribute to the mechanisms of central sensitization. CONCLUSIONS: It tempting to speculate that ongoing nociception is associated with cortical and subcortical reorganization and may play an important role in the process of the chronification of LBP. Future prospective research should explore to what extent these changes are reversible and if this reversibility is associated with improved functioning of patients