Background & Aims

Chronic neck pain is a prevalent and disabling condition, affecting up to 70% of the global population at least once in their lives [1,2]. While physical exercise therapy is a promising and primary treatment for chronic nonspecific neck pain [3], its effectiveness varies [4]. A potential explanation is the differing central endogenous pain modulatory responses among individuals. While some people experience exercise-induced hypoalgesia, others show hyperalgesic effects of exercise [5]. This study aims to investigate the central neurobiological characteristics that may contribute to these differential effects. Our primary goal is to examine alterations in structural brain characteristics after exercise therapy for chronic nonspecific neck pain. Our secondary aims are to investigate (1) baseline differences in structural brain characteristics between exercise therapy responders and non-responders, and (2) divergent brain changes after exercise therapy among responders and non-responders.

Methods

This prospective longitudinal cohort study included 24 participants (18 female, mean age 39.7 years) with chronic nonspecific neck pain. Participants underwent two data-collection sessions: one before the eight-week exercise intervention and one within a week of completing it. Both sessions encompassed questionnaires and neuroimaging. The intervention comprised an eight-week physical exercise program, involving two physiotherapist-delivered sessions per week (total 16 sessions) and one independent session per week. Freesurfer cluster-wise analysis assessed structural changes from baseline to follow-up. Volume and thickness measures were then extracted for individual regions of interest (ROIs). Responders, defined as those with ?20% improvement on the Neck Disability Index (NDI), were distinguished from non-responders, who exhibited <20% improvement.

Results

On average, participants improved 56% on the NDI (mean difference [SD]: 9.3 [5.2], 95% CI: 7.1 to 11.5, p<.001). Overall, 13/24 (54%) participants were identified as responders, and 11/24 (46%) participants were identified as non-responders. At baseline, we found a larger postcentral gyrus volume in non-responders compared to responders (cluster-weighted p-value [CWP]: 0.0068). ROI analysis found larger values in non-responders for: postcentral volume (p=0.031), and caudal middle frontal (p=0.020), postcentral (p=0.041), precentral (p=0.004), rostral middle and superior frontal thickness (p=0.033). We found differences in baseline to follow-up changes between responders and non-responders for bilateral insular volume (CWP=0.00020). ROI analysis further identified different changes for: thalamus (p=0.021) and rostral anterior cingulate volume (p=0.0035), and caudal middle frontal (p=0.0125), isthmus and posterior cingulate (p=0.0265, p=0.0418), and orbitofrontal thickness (p=0.023).

Conclusions

This study aimed to investigate brain changes after physical exercise therapy for chronic nonspecific neck pain. The identification of responders and non-responders to exercise therapy allowed us to investigate baseline differences between these groups, and different brain changes after the intervention. Across all participants with chronic nonspecific neck pain, we found numerous brain changes following the 8-week physical exercise intervention. Importantly, we found baseline differences in brain characteristics between responders and non-responders to exercise therapy, and after exercise therapy we found that the various regions increased in volume or thickness in non-responders, but decreased in responders. These results suggest that central mechanisms may contribute to the differential effects of exercise therapy between patients with chronic nonspecific neck pain. These findings may be used in future to enhance personalised treatment approaches.

References

1. Fejer R, Kyvik KO, Hartvigsen J. The prevalence of neck pain in the world population: a systematic critical review of the literature. Eur Spine J. Jun 2006;15(6):834-48. doi:10.1007/s00586-004-0864-4
2. Safiri S, Kolahi AA, Hoy D, et al. Global, regional, and national burden of neck pain in the general population, 1990-2017: systematic analysis of the Global Burden of Disease Study 2017. BMJ. Mar 26 2020;368:m791. doi:10.1136/bmj.m791
3. Sterling M, de Zoete RMJ, Coppieters I, Farrell SF. Best Evidence Rehabilitation for Chronic Pain Part 4: Neck Pain. J Clin Med. Aug 15 2019;8(8)doi:10.3390/jcm8081219
4. de Zoete RMJ, Nikles J, Coombes JS, Onghena P, Sterling M. The effectiveness of aerobic versus strengthening exercise therapy in individuals with chronic whiplash-associated disorder: a randomised single case experimental design study. Disabil Rehabil. Sep 29 2022:1-10. doi:10.1080/09638288.2022.2127937
5. Smith A, Ritchie C, Pedler A, McCamley K, Roberts K, Sterling M. Exercise induced hypoalgesia is elicited by isometric, but not aerobic exercise in individuals with chronic whiplash associated disorders. Scand J Pain. Apr 2017;15:14-21. doi:10.1016/j.sjpain.2016.11.007

Presenting Author

Rutger de Zoete

Poster Authors

Rutger Zoete

BSc, MSc, PhD

The University of Adelaide, Adelaide, South Australia, Australia

Lead Author

Carolyn Berryman

PhD

University of South Australia

Lead Author

Jo Nijs

PhD

Vrije Universiteit Brussel

Lead Author

Angela Walls

MMSc

South Australian Health and Medical Research Institute

Lead Author

Mark Jenkinson

PhD

The University of Adelaide

Lead Author

Topics

  • Specific Pain Conditions/Pain in Specific Populations: Neck Pain