Background & Aims
People with chronic whiplash-associated disorders (WAD) may present with clinical features suggestive of central sensitization (CS)1. The mechanisms underlying CS are largely unknown, although it has been demonstrated that CS can be attenuated following reduction of nociception2. Central Sensitization may result from impaired descending pain modulation3, which has been shown in chronic WAD4. Offset analgesia (OffA) is a testing regime that evaluates descending pain modulation5, demonstrating a disproportionate reduction in reported pain intensity following a small reduction in evoked noxious stimulus5. This has not previously been tested in chronic WAD. The aims of this study were to determine 1) if reduction of nociception was significantly associated with improved descending pain modulation, as measured with the OffA regime, and 2) if OffA was associated with clinical manifestations of chronic WAD.
Methods
Participants with WAD II (demonstrable cervicogenic musculoskeletal signs and symptoms without neurological compromise or cervical fracture) aged 18-65 years were invited to participate in the study if they reported >80% relief of pain after receiving a single round of diagnostic medial branch blocks (MBBs) of putative cervical facet joint(s). Offset analgesia was tested prior to and following MBBs. A ‘standard-OffA’ paradigm was applied to the left lateral forearm at a predetermined heat pain threshold reflecting evoked pain of 60/100 (t1 = HPT60; t2 = +1⁰C; t3 = HPT60). A constant stimulus of HPT60 was applied as control (pre- and post-MBBs) for the evoked pain. OffA calculated the percentage difference in (t3-t2)/t2 ratios between the control and testing paradigms. Paired t-tests evaluated if the OffA ratio was significantly different pre/post-MBBs. Pearson’s r correlations compared OffA versus pre-procedural pain intensity (NPRS), physical activity levels (IPAQ) and self-reported SF-12 physical and mental health related quality of life (QOL).
Results
19 people (14 female) with a mean (SD) age of 41.0 (9.3) years with chronic WAD of a mean (SD) duration of 23.4 ± 9.8 months participated in the study. Offset analgesia was elicited in participants both prior to (mean ± SD: -36% ± 43% pain relief) and following (-46% ± 52%) MBBs. There was no significant difference in OffA following MBBs (t18 = -0.79; p = 0.44). Prior to MBBs, less efficacious OffA was associated with higher levels of self-reported mental health QOL (r = -0.51, p = 0.045) and lower levels of disability (r = 0.49, p = 0.032). Post-MBB, reduced OffA was not associated with any clinical manifestations.
Conclusions
Although OffA was effectively elicited in people with chronic WAD, there was no significant difference in OffA efficacy when nociception was effectively abolished, indicating that peripheral nociception is unlikely to underpin the underlying mechanisms associated with the OffA testing paradigm. Interestingly, when people were experiencing moderate-to-severe levels of neck pain (pre-MBB), lower levels of mental health QOL and higher levels of disability were associated with efficacious OffA and inversely, higher levels of mental health QOL and lower levels of disability were associated with less-efficacious OffA. In the absence of nociception (post-MBB), efficacious OffA was not associated with any clinical manifestations. In concert, these results suggest that clinical features of a person’s pain experience not associated with nociception are more likely underpinning the OffA testing paradigm.
References
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- Smith AD, Jull G, Schneider GM, Frizzell B, Hooper RA, Sterling M. PM R 2015;7(9):913-21. DOI: 10.1016/j.pmrj.2015.03.014.
- Yarnitsky D, Granot M, Granovsky Y. Pain 2014;155(4):663-5. DOI: 10.1016/j.pain.2013.11.005.
- Ng TS, Pedler A, Vicenzino B, Sterling M. Clin J Pain 2013;30(5):436-42.
- Grill JD, Coghill RC. J Neurophysiol 2002;87(4):2205-8. DOI: 10.1152/jn.00730.2001.
Presenting Author
Ashley Smith
Poster Authors
Topics
- Specific Pain Conditions/Pain in Specific Populations: Neck Pain