Background & Aims

Chronic pain (CP) is a major public health issue worldwide, with high treatment failure rate and heavy burden. Among strategies proposed to improve analgesia, a better characterization and classification of CP syndromes can be achieved through association of objective indicators to the currently validated subjective pain scales. Resting-state EEG indicators were recently proposed to be biomarkers of chronic neuropathic pain (CNP) as defined by the IASP. However, their relationship with clinical neuropathic features of pain (found also in other pain types) was not questioned.

Methods

In this new retrospective analysis of existing data, two lower-limb radiculopathy-related CNP populations (CNP1, n=9; CNP2, n=10; all right-handed males), 16 fibromyalgia (FM) female and right-handed patients were investigated regarding mainly VAS and DN4 scores, while mood (HAD) and sleep (ISI) scales were only used to characterize the studied populations. High-density (64 electrodes) resting-state EEG recording data were also analyzed. The Global power spectrum (GPS) derived from a Fast Fourier Transform-based spectral analysis of preprocessed data was used to characterize each frequency domain: high ? (H?; 20-30 Hz), low ? (L?; 13-20 Hz), ? (8-12 Hz), ? (7-8 Hz) and ? (2-4 Hz). Standard statistical descriptive and inferential parametric tests were performed, and significance set at p<0.05 (95% CI, two-tailed). All results presented below are beyond statistical significance.

Results

All 3 groups (CNP1, CNP2 and FM) had similar age, ongoing pain (VASd~4/10) and DN4 (~6), subclinical anxiety and insomnia; FM patients showed higher general pain (VASg~6/10) and depression sub-score. The CNP1 group displayed correlations between DN4 and VASg and between VASd and VASg, whereas no correlation was seen in the CNP2 group. In the FM group, DN4 was correlated with VASg. The CNP1 (contrary to CNP2 and FM) patients with significant pain (VASd?3) showed a correlation between L? GPS and VASd (r=-0.909).
Discrepancies between CNP1 and CNP2 populations were analyzed in relation with past back surgery as the only discriminating element (22 % vs 80% and 1042(42) vs 260(358) days delay to evaluation). In the non-back surgery group, correlations between DN4 and VASd; between VASd and VASg and between H? GPS and both VASd (r=-0.682) and DN4 (-0.690) were found, in contrast to absence of correlation in the back surgery group.

Conclusions

High and low ? GPS seem to be related to ongoing pain intensity in CNP, but not to the clinical neuropathic character of pain (which is associated to the general pain level). Recent back surgical intervention vanishes most clinical associations in CNP, while a link appears now between H? GPS and the clinical neuropathic feature of pain; suggesting some impact beyond the desired therapeutic effect.

References

Mussigmann, T et al. (2022), NeuroImage, 258:119355,
Mouraux, A et al. (2018), Brain, 141:3290-3307

Presenting Author

Joelle N. Chabwine

Poster Authors

Joelle Chabwine

MD, PhD

University of Fribourg

Lead Author

Igor Gossuin

Department of Orthopedics, Fribourg Hospital, Fribourg, Switzerland

Lead Author

Renato Gondar

Department of Orthopedics, Fribourg Hospital, Fribourg, Switzerland

Lead Author

Franziska Peier

MSc

Laboratory for Neurorehabilitation Science, Medicine Section, University of Fribourg, Switzerland

Lead Author

Naima L. Mory

MSc

Laboratory for Neurorehabilitation Science, Medicine Section, University of Fribourg, Switzerland

Lead Author

Gianluca Maestretti

MD

Department of Orthopedics, Fribourg Hospital, Fribourg, Switzerland

Lead Author

Michael De Pretto

PhD

Laboratory for Neurorehabilitation Science, Medicine Section, University of Fribourg, Switzerland

Lead Author

Michael Mouthon

PhD

Laboratory for Neurorehabilitation Science, Medicine Section, University of Fribourg, Switzerland

Lead Author

Topics

  • Specific Pain Conditions/Pain in Specific Populations: Neuropathic Pain - Peripheral