Neurophysiological oscillatory markers of hypoalgesia in conditioned pain modulation

Introduction:Conditioned pain modulation (CPM) is an experimental procedure that consists of an ongoing noxious stimulus attenuating the pain perception caused by another noxious stimulus. A combination of the CPM paradigm with concurrent electrophysiological recordings can establish whether an association exists between experimentally modified pain perception and modulations of neural oscillations.Objectives:We aimed to characterize how CPM modifies pain perception and underlying neural oscillations. We also interrogated whether these perceptual and/or neurophysiological effects are distinct in patients affected by chronic pain.Methods:We presented noxious electrical stimuli to the right ankle before, during, and after CPM induced by an ice pack placed on the left forearm. Seventeen patients with chronic pain and 17 control participants rated the electrical pain in each experimental condition. We used magnetoencephalography to examine the anatomy-specific effects of CPM on the neural oscillatory responses to the electrical pain.Results:Regardless of the participant groups, CPM induced a reduction in subjective pain ratings and neural responses (beta-band [15-35 Hz] oscillations in the sensorimotor cortex) to electrical pain.Conclusion:Our findings of pain-induced beta-band activity may be associated with top-down modulations of pain, as reported in other perceptual modalities. Therefore, the reduced beta-band responses during CPM may indicate changes in top-down pain modulations.</p

Magnetoencephalography reveals increased slow-to-fast alpha power ratios in patients with chronic pain

INTRODUCTION: Objective disease markers are a key for diagnosis and personalized interventions. In chronic pain, such markers are still not available, and therapy relies on individual patients' reports. However, several pain studies have reported group-based differences in functional magnetic resonance imaging, electroencephalography, and magnetoencephalography (MEG). OBJECTIVES: We aimed to explore spectral differences in resting-state MEG brain signals between patients with chronic pain and pain-free controls and to characterize the cortical and subcortical regions involved. METHODS: We estimated power spectral density over 5 minutes of resting-state MEG recordings in patients with chronic pain and controls and derived 7 spectral features at the sensor and source levels: alpha peak frequency, alpha power ratio (power 7–9 Hz divided by power 9–11 Hz), and average power in theta, alpha, beta, low-gamma, and high-gamma bands. We performed nonparametric permutation t tests (false discovery rate corrected) to assess between-group differences in these 7 spectral features. RESULTS: Twenty-one patients with chronic pain and 25 controls were included. No significant group differences were found in alpha peak frequency or average power in any frequency band. The alpha power ratio was significantly higher (P < 0.05) in patients with chronic pain at both the sensor and brain source levels. The brain regions showing significantly higher ratios included the occipital, parietal, temporal and frontal lobe areas, insular and cingulate cortex, and right thalamus. CONCLUSION: The alpha power ratio is a simple, promising signal marker of chronic pain, affecting an expansive range of cortical and subcortical regions, including known pain-processing areas

Heterogeneous Cortical Effects of Spinal Cord Stimulation

Objectives: The understanding of the cortical effects of spinal cord stimulation (SCS) remains limited. Multiple studies have investigated the effects of SCS in resting-state electroencephalography. However, owing to the large variation in reported outcomes, we aimed to describe the differential cortical responses between two types of SCS and between responders and nonresponders using magnetoencephalography (MEG). Materials and Methods: We conducted 5-minute resting-state MEG recordings in 25 patients with chronic pain with active SCS in three sessions, each after a one-week exposure to tonic, burst, or sham SCS. We extracted six spectral features from the measured neurophysiological signals: the alpha peak frequency; alpha power ratio (power 7–9 Hz/power 9–11 Hz); and average power in the theta (4–7.5 Hz), alpha (8–12.5 Hz), beta (13–30 Hz), and low-gamma (30.5–60 Hz) frequency bands. We compared these features (using nonparametric permutation t-tests) for MEG sensor and cortical map effects across stimulation paradigms, between participants who reported low (&lt; 5, responders) vs high (≥ 5, nonresponders) pain scores, and in three representative participants. Results: We found statistically significant (p &lt; 0.05, false discovery rate corrected) increased MEG sensor signal power below 3 Hz in response to burst SCS compared with tonic and sham SCS. We did not find statistically significant differences (all p &gt; 0.05) between the power spectra of responders and nonresponders. Our data did not show statistically significant differences in the spectral features of interest among the three stimulation paradigms or between responders and nonresponders. These results were confirmed by the MEG cortical maps. However, we did identify certain trends in the MEG source maps for all comparisons and several features, with substantial variation across participants. Conclusions: The considerable variation in cortical responses to the various SCS treatment options necessitates studies with sample sizes larger than commonly reported in the field and more personalized treatment plans. Studies with a finer stratification between responders and nonresponders are required to advance the knowledge on SCS treatment effects.</p

The Effect of Various Spinal Neurostimulation Paradigms on the Supraspinal Somatosensory Evoked Response:A Systematic Review

Introduction: Spinal neurostimulation is a therapy for otherwise intractable chronic pain. Spinal neurostimulation includes stimulation of the spinal cord (SCS), dorsal root ganglion (DRGS), and dorsal root entry zone (DREZS). New paresthesia-free neurostimulation paradigms may rely on different mechanisms of action from those of conventional tonic neurostimulation. The aim of this systematic review is to assess the existing knowledge on the effect of spinal neurostimulation on somatosensory processing in patients with chronic pain. We therefore reviewed the existing literature on the effect of various spinal neurostimulation paradigms on the supraspinal somatosensory evoked response (SER). Materials and Methods: Multiple scientific data bases were searched for studies that assessed the effect of spinal neurostimulation on the supraspinal SER, evoked by painful or nonpainful peripheral stimuli in patients with chronic pain. We found 205 studies, of which 24 were included. Demographic data, study design, and study outcome were extracted. Results: Of the 24 included studies, 23 used electroencephalography to assess the SER; one study used magnetoencephalography. Fifteen studies evaluated tonic SCS; six studies (also) evaluated paresthesia-free paradigms; three studies evaluated the effect of tonic DRGS or DREZS. Sixteen studies used nonpainful stimuli to elicit the SER, 14 observed a decreased SER amplitude. Ten studies used painful stimuli to elicit the SER, yielding mixed results. Discussion: The included studies suggest that both paresthesia-based and paresthesia-free spinal neurostimulation paradigms can decrease (part of) the SER elicited by a nonpainful peripheral stimulus. The observed SER amplitude reduction likely is the effect of various spinal and supraspinal mechanisms of spinal neurostimulation that also contribute to pain relief. Conclusions: Spinal neurostimulation modulates the processing of a peripherally applied nonpainful stimulus. For painful stimuli, the results are not conclusive. It is not yet clear whether paresthesia-free neurostimulation affects the SER differently from paresthesia-based neurostimulation.</p

A multidisciplinary approach on music induced-analgesia differentiated by socio-cultural background in healthy volunteers (MOSART):A cross-over randomized controlled trial protocol

Background:Integrating music into pain treatment demonstrates significant benefits, effectively reducing subjective pain levels and perioperative opioid requirements. Currently, the relationship between the impact of specific types of music and listeners’ socio-cultural background is still unclear. This is especially relevant given that sociological research indicates that these factors can have a notable influence on music preference and perception. Current evidence suggests that individuals who choose their own music may experience greater benefits. However, additional research is needed to comprehensively grasp whether the effect of (preferred) music on pain endurance remains consistent across different socio-cultural backgrounds.Methods:In this study, a collaborative effort between medical and sociological researchers aims to investigate music-induced analgesia differentiated by socio-cultural background in healthy volunteers. Participants (n=84) will listen to self-, and researcher-chosen music and a podcast as a control condition in a cross-over study design. The primary outcome of this study is pain endurance measured by electric stimuli of increasing intensity. Detailed sociological validated questionnaires will be utilized. Considering the notable influence of educational level on music taste formation found in previous research and its crucial role as a source of socio-cultural differentiation, participants will be stratified based on their level of education.Discussion:This experimental study represents one of the first efforts to gain a socio-culturally differentiated understanding of the therapeutic potential of music. Consequently, this could pave the way to purposefully and inclusively implement personalized music in healthcare settings

A multidisciplinary approach on music induced-analgesia differentiated by socio-cultural background in healthy volunteers (MOSART):A cross-over randomized controlled trial protocol

Background:Integrating music into pain treatment demonstrates significant benefits, effectively reducing subjective pain levels and perioperative opioid requirements. Currently, the relationship between the impact of specific types of music and listeners’ socio-cultural background is still unclear. This is especially relevant given that sociological research indicates that these factors can have a notable influence on music preference and perception. Current evidence suggests that individuals who choose their own music may experience greater benefits. However, additional research is needed to comprehensively grasp whether the effect of (preferred) music on pain endurance remains consistent across different socio-cultural backgrounds.Methods:In this study, a collaborative effort between medical and sociological researchers aims to investigate music-induced analgesia differentiated by socio-cultural background in healthy volunteers. Participants (n=84) will listen to self-, and researcher-chosen music and a podcast as a control condition in a cross-over study design. The primary outcome of this study is pain endurance measured by electric stimuli of increasing intensity. Detailed sociological validated questionnaires will be utilized. Considering the notable influence of educational level on music taste formation found in previous research and its crucial role as a source of socio-cultural differentiation, participants will be stratified based on their level of education.Discussion:This experimental study represents one of the first efforts to gain a socio-culturally differentiated understanding of the therapeutic potential of music. Consequently, this could pave the way to purposefully and inclusively implement personalized music in healthcare settings