Longitudinal changes in human supraspinal processing after RIII-feedback training to improve descending pain inhibition.

The human body has the ability to influence its sensation of pain by modifying the transfer of nociceptive information at the spinal level. This modulation, known as descending pain inhibition, is known to originate supraspinally and can be activated by a variety of ways including positive mental imagery. However, its exact mechanisms remain unknown. We investigated, using a longitudinal fMRI design, the brain activity leading up and in response to painful electrical stimulation when applying positive mental imagery before and after undergoing a previously established RIII-feedback paradigm. Time course analysis of the time preceding painful stimulation shows increased haemodynamic activity during the application of the strategy in the PFC, ACC, insula, thalamus, and hypothalamus. Time course analysis of the reaction to painful stimulation shows decreased reaction post-training in brainstem and thalamus, as well as the insula and dorsolateral PFC. Our work suggests that feedback training increases activity in areas involved in pain inhibition, while simultaneously decreasing the reaction to painful stimuli in brain areas related to pain processing, which points to an activation of decreased spinal nociception. We further suggest that the insula and the thalamus may play a more important role in pain modulation than previously assumed.

Effects of Introvision, a self-regulation method with a mindfulness-based perception technique in migraine prevention: a monocentric randomized waiting-list controlled study (IntroMig Study).

BACKGROUND: Migraine is a brain disorder with recurrent headache attacks and altered sensory processing. Introvision is a self-regulation method based on mindfulness-like perception techniques, developed at the University of Hamburg. Here, we examined the effect of Introvision in migraine prevention. METHODS: Migraineurs with at least five headache days per month were block-randomized to the experimental group (EG) or waiting list group (WL), the latter starting Introvision training six weeks after the EG. Participants learned Introvision in six weekly on-site group sessions with video-conference support followed by three individual video-conference sessions. Headache diaries and questionnaires were obtained before Introvision training and three months after the last individual Introvision session. RESULTS: Fifty-one patients completed the study. The primary outcome, headache days of the EG after Introvision training compared to those of the WL before the training, showed no significant effect (10.6 ± 7.7, n = 22; vs. 10.9 ± 6.3, n = 29, p = 0.63; Mann-Whitney-U-Test). The secondary outcome, comparing pooled EG and WL data before and after Introvision training, revealed a significant reduction of headache days (from 11.7 ± 6.5 to 9.8 ± 7.0; p = 0.003; Wilcoxon-paired-Test) as well as of acute medication intake and Headache-Impact-Test 6 (HIT-6) scores and increased self-efficacy as quantified by increased FKMS-scores (FKMS: german short form of the Headache Management Self-Efficacy Scale (HMSE)). CONCLUSION: Although the study did not reach its primary endpoint, several secondary outcome parameters in the pooled (non-controlled) pre-post analysis showed an improvement with a decrease in monthly headache days by 1.9 days/ month. A larger randomized controlled trial has to corroborate these preliminary findings. TRIAL REGISTRATION: NCT03507400, Registration date 09.03.2018.

Static magnetic field exposure in 1.5 and 3 Tesla MR scanners does not influence pain and touch perception in healthy volunteers.

BACKGROUND: Magnetic field therapy is a popular approach to pain therapy, but scientific evidence on treatment effects or even effects on sensory and pain perception in healthy controls is scarce. METHODS: In the present randomized, placebo-controlled study, we investigated the influence of static magnetic field exposure on sensory (touch) and pain (pinprick, pressure and heat) perception. Eighteen healthy volunteers (age: 23 ± 2 years, nine women) underwent three 10-min static magnetic field exposures using field strengths of 0 T (placebo), 1.5 T and 3 T within clinical MR scanners in randomized order on three separate days. Participants were blinded to magnetic field strength. Experimental sensory and pain testing was performed immediately before and after each magnetic field exposure. RESULTS: There was no significant effect of field strength on the assessed experimental sensory and pain testing parameters (mechanical detection threshold, pinprick threshold, pressure pain threshold, heat pain threshold and suprathreshold heat pain rating). CONCLUSION: We found no evidence that a 10-min 1.5 T or 3 T static magnetic field exposure affects experimental sensory or pain perception in young healthy volunteers. SIGNIFICANCE: We used clinical MR scanners to investigate the effect of magnetic fields on pain perception. Using a rigorous, straightforward, placebo-controlled design, no effect of static magnetic fields on human experimental pain perception was detected. This provides a base for a more systematic investigation of magnetic field effects on pain.

Learned control over spinal nociception: Transfer and stability of training success in a long-term study.

OBJECTIVE: Healthy subjects can learn to use cognitive-emotional strategies to suppress their spinal nociception, quantified by the nociceptive flexor reflex (RIII reflex), when given visual RIII feedback. This likely reflects learned activation of descending pain inhibition. Here, we investigated if training success persists 4 and 8 months after the end of RIII feedback training, and if transfer (RIII suppression without feedback) is possible. METHODS: 18 and 8 subjects who had successfully completed feedback training were investigated 4 and 8 months later. RESULTS: At 4 months, RIII suppression during feedback and transfer was similar to that achieved at the final RIII feedback training session (to 50 ±â€¯22%, 53 ±â€¯21% and 52 ±â€¯21% of baseline, all differences n.s.). At 8 months, RIII suppression was somewhat (not significantly) smaller in the feedback run (to 64 ±â€¯17%) compared to the final training session (56 ±â€¯19%). Feedback and transfer runs were similar (to 64 ±â€¯17% vs. 68 ±â€¯24%, n.s.). Concomitant reductions in pain intensity ratings were stable at 4 and 8 months. CONCLUSIONS: RIII feedback training success was completely maintained after 4 months, and somewhat attenuated 8 months after training. Transfer was successful. SIGNIFICANCE: These results are an important pre-requisite for application of RIII feedback training in the context of clinical pain.

Responsiveness of the autonomic nervous system during paced breathing and mental stress in migraine patients.

BACKGROUND: Migraine is a stress-related disorder, suggesting that there may be sympathetic hyperactivity in migraine patients. However, there are contradictory results concerning general sympathetic activation in migraine patients. To shed more light on the involvement of the autonomic nervous system (ANS) in migraine pathophysiology, we investigated cardiac and cardiovascular reactions during vagal (paced breathing) and sympathetic activation (mental stress test). METHODS: Heart rate variability parameters and skin conductance responses were recorded interictally in 22 episodic migraine patients without aura and 25 matched controls during two different test conditions. The paced breathing test consisted of a five-minute baseline, followed by two minutes of paced breathing (6 breathing cycles per minute) and a five-minute recovery phase. The mental stress test consisted of a five-minute baseline, followed by one minute of stress anticipation, three and a half minutes of mental stress and a five-minute recovery phase. Furthermore we measured blood pressure and heart rate once daily over 2 weeks. Subjects rated their individual current stress level and their stress level during paced breathing and during the mental stress test. RESULTS: There were no significant differences between migraine patients and controls in any of the heart rate variability parameters in either time domain or frequency domain analysis. However, all parameters showed a non-significant tendency for larger sympathetic activation in migraine patients. Also, no significant differences could be observed in skin conductance responses and average blood pressure. Only heart rates during the 2-week period and stress ratings showed significantly higher values in migraine patients compared to controls. CONCLUSIONS: Generally there were no significant differences between migraine patients and controls concerning the measured autonomic parameters. There was a slight but not significant tendency in the migraine patients to react with less vagal and more sympathetic activation in all these tests, indicating a slightly changed set point of the autonomic system. Heart rate variability and blood pressure in migraine patients should be investigated for longer periods and during more demanding sympathetic activation.

Learned control over spinal nociception reduces supraspinal nociception as quantified by late somatosensory evoked potentials.

We have recently shown that subjects can learn to use cognitive-emotional strategies to suppress their spinal nociceptive flexor reflex (RIII reflex) under visual RIII feedback and proposed that this reflects learned activation of descending pain inhibition. Here, we investigated whether learned RIII suppression also affects supraspinal nociception and whether previous relaxation training increases success. Subjects were trained over 3 sessions to reduce their RIII size by self-selected cognitive-emotional strategies. Two groups received true RIII feedback (with or without previous relaxation training) and a sham group received false feedback (15 subjects per group). RIII reflexes, late somatosensory evoked potentials (SEPs), and F-waves were recorded and pain intensity ratings collected. Both true feedback groups achieved significant (P < 0.01) but similar RIII suppression (to 79% ± 21% and 70% ± 17% of control). Somatosensory evoked potential amplitude (100-150 milliseconds after stimulation) was reduced in parallel with the RIII size (r = 0.57, P < 0.01). In the sham group, neither RIII size nor SEP amplitude was significantly reduced during feedback training. Pain intensity was significantly reduced in all 3 groups and also correlated with RIII reduction (r = 0.44, P < 0.01). F-wave parameters were not affected during RIII suppression. The present results show that learned RIII suppression also affects supraspinal nociception as quantified by SEPs, although effects on pain ratings were less clear. Lower motor neuron excitability as quantified by F-waves was not affected. Previous relaxation training did not significantly improve RIII feedback training success.

Headache in children: update on biobehavioral treatments.

Biobehavioral pain treatment consists of relaxation techniques, biofeedback treatment, operant pain treatment, pain coping, cognitive-behavioral treatment, and multimodal treatment. Especially in the treatment of pediatric headache, biobehavioral procedures have been found to be highly efficient and are widely accepted. They present similar effects as pharmaceutical treatments. In general, when standardized treatment programs are applied, the sessions are highly effective.

The effect of distraction strategies on pain perception and the nociceptive flexor reflex (RIII reflex).

Distraction from pain reduces pain perception, and imaging studies have suggested that this may at least partially be mediated by activation of descending pain inhibitory systems. Here, we used the nociceptive flexor reflex (RIII reflex) to directly quantify the effects of different distraction strategies on basal spinal nociception and its temporal summation. Twenty-seven healthy subjects participated in 3 distraction tasks (mental imagery, listening to preferred music, spatial discrimination of brush stimuli) and, in a fourth task, concentrated on the painful stimulus. Results show that all 3 distraction tasks reduced pain perception, but only the brush task also reduced the RIII reflex. The concentration-on-pain task increased both pain perception and the RIII reflex. The extent of temporal summation of pain perception and the extent of temporal summation of the RIII reflex were not affected by any of the tasks. These results suggest that some, but not all, forms of pain reduction by distraction rely on descending pain inhibition. In addition, pain reduction by distraction seems to preferentially affect mechanisms of basal nociceptive transmission, not of temporal summation.