Conditioned Pain Modulation in Chronic Low Back Pain

Abstract

Objective: The objective of the review is to determine whether conditioned pain modulation (CPM) is impaired in adults with chronic low back pain (CLBP) when compared with pain-free individuals. Methods: A a systematic search of the literature was undertaken using the databases: MEDLINE, Scopus, CINAHL and Web of Science. The citations of included studies were reviewed for additional studies. Observational, cross-sectional, case-control studies published in English between January 1990 and August 2019 were considered. Studies that investigated the efficiency of standardized CPM regimens among defined cases of CLBP and in comparison, with pain-free controls were included. After initial title and abstract screening, 2 authors reviewed the full texts of the eligible articles independently. Risk of bias was carried out using assessment of 4 categories: blinding of the outcome assessors, representativeness of cases to the specified population, comparability of cases and controls, and control of confounding variables. Results: In total, 643 records were identified, of which 7 studies were included. Overall, the results of the studies reported mixed conclusions on the efficiency of CPM in CLBP. Three studies identified significant differences for CPM between CLBP and pain-free controls and the other 4 studies reported no significant differences. The common methodological limitations were unclear reporting about blinding of the outcome assessors and inadequate control of confounding factors. Conclusions: High-quality research is strongly recommended to determine the function of endogenous pain modulatory mechanisms in CLBP.

Epigenome-wide DNA methylation profiling of conditioned pain modulation in individuals with non-specific chronic low back pain

“…Also, we did not observe any significant differences in subjective pain measures (BPI pain severity and interference) between efficient and deficient CPM in individuals with cLBP. Our findings are consistent with recent systematic reviews that revealed a lack of strong relationship between CPM efficiency and cLBP [ 17 , 67 ]. Three additional observations from our data may support this observation: (1) more pathways were enriched in the PFC than cLBP group, (2) there was more overlap in GO and functional pathways between PFC and cLBP groups than unique cLBP pathways, and (3) the PFC group had more unique pathways than cLBP group.…”

“…Specifically, it has been suggested that enhanced pain sensitivity and deficient CPM correlate with greater cLBP severity and disability [ 16 ]. More recently, two systematic reviews found that individuals with cLBP have significantly reduced CPM [ 17 ] and pressure pain thresholds (PPTs) [ 8 ]. Thus, it is possible that nonspecific cLBP is related to alterations in descending pain modulatory pathways.…”

Quantitative Sensory Testing Discriminates Central Sensitization Inventory Scores in Participants with Chronic Musculoskeletal Pain: An Exploratory Study

“…This finding implies a potential benefit to using pain duration, but a limitation in using pain intensity, to infer a participant’s pain mechanism. Multiple studies have suggested that pain intensity does not correlate strongly with QST 41–43 . A poor relationship was found between PPT and pain intensity, whereas a fair relationship was found for TS, in mixed samples with spinal pain 41 .…”

“…Regional hyperalgesia and decreased conditioned pain modulation (CPM) are indicative of CS and have been shown in subjects with whiplash‐associated disorder compared with subjects with chronic neck pain 44 . However, mixed results have been reported for using CPM in subjects with LBP, as CPM has not been shown to be a good prognostic tool for severe sciatica 43,45 . Future studies should continue to investigate the utility of testing for regional hyperalgesia, allodynia, and altered pain processing (TS or CPM) to more accurately identify alterations in central pain modulation present in subjects with chronic musculoskeletal pain.…”

Within-session test-retest reliability of pressure pain threshold and mechanical temporal summation in healthy subjects

“…Recently, these paradigms have been increasingly used in research to determine if individuals with chronic pain have an altered pain inhibition response. For example, some studies reported an alteration of pain inhibition in individuals with chronic low back pain (CLBP) using CPM [6][7][8][9] and EIH [10,11].…”