Distraction by a cognitive task has a higher impact on electrophysiological measures compared with conditioned pain modulation

Posttraumatic headache: pain related evoked potentials (PREP) and conditioned pain modulation (CPM) to assess the pain modulatory function

Posttraumatic headache (PTH) is common following traumatic brain injury and impacts quality of life. We investigated descending pain modulation as one possible mechanism for PTH and correlated it to clinical measures. Pain-related evoked potentials (PREP) were recorded in 26 PTH-patients and 20 controls after electrical stimulation at the right hand and forehead with concentric surface electrodes. Conditioned pain modulation (CPM) was assessed using painful cutaneous electric stimulation (PCES) on the right hand as test stimulus and immersion of the left hand into 10 °C-cold water bath as conditioning stimulus based on changes in pain intensity and in amplitudes of PCES-evoked potentials. All participants completed questionnaires assessing depression, anxiety, and pain catastrophising. PTH-patients reported significantly higher pain ratings during PREP-recording in both areas despite similar stimulus intensity at pain threshold. N1P1-amplitudes during PREP and CPM-assessment were lower in patients in both areas, but statistically significant only on the hand. Both, PREP-N1-latencies and CPM-effects (based on the N1P1-amplitudes and pain ratings) were similar in both groups. Patients showed significantly higher ratings for anxiety and depression, which did not correlate with the CPM-effect. Our results indicate generalized hyperalgesia for electrical stimuli in both hand and face in PTH. The lacking correlation between pain ratings and EEG parameters indicates different mechanisms of pain perception and nociception.

Effect of Mirror Therapy on Post-Needling Pain Following Deep Dry Needling of Myofascial Trigger Point in Lateral Elbow Pain: Prospective Controlled Pilot Trial

Background: This prospective randomized, controlled pilot trial to explore the immediate effect of adding Mirror Visual Feedback Therapy on pain sensitivity and motor performance among subjects suffering from post-needling pain diagnosed as Lateral Elbow Pain. Methods: A total of 49 participants (23 female, 26 male) were enrolled and randomly allocated to either the experimental group, which received Deep Dry Needling in the m. Brachioradialis, Ischemic Compression, Cold Spray, Stretching, and Mirror Visual Feedback Therapy (n = 25), or a control group without Mirror Visual Feedback Therapy (n = 24). Pre- and post-treatment evaluations included assessments of post-needling pain intensity, pressure pain threshold, two-point discrimination threshold, and maximum hand grip strength. Results: Intergroup analysis revealed a statistically significant reduction in post-needling pain intensity favoring the experimental group (U = 188.00, p = 0.034). Additionally, intragroup analysis showed significant improvements in post-needling pain intensity (MD = 0.400, SEM = 0.271, W = 137.00, p = 0.047) and pressure pain threshold (MD = 0.148 Kg/cm2, SEM = 0.038, W = 262.00, p < 0.001) within the experimental group following the intervention. Conclusions: These findings suggest a potential benefit of integrating Mirror Visual Feedback Therapy into treatment protocols for individuals with Lateral Elbow Pain experiencing post-needling discomfort. Further research is necessary to fully elucidate the clinical implications of these findings.

Neural mechanisms underlying the conditioned pain modulation response: a narrative review of neuroimaging studies

ABSTRACT

Processing spatially distributed nociceptive information is critical for survival. The conditioned pain modulation (CPM) response has become a common psychophysical test to examine pain modulation capabilities related to spatial filtering of nociceptive information. Neuroimaging studies have been conducted to elucidate the neural mechanisms underlying the CPM response in health and chronic pain states, yet their findings have not been critically reviewed and synthesized before. This narrative review presents a simplified overview of MRI methodology in relation to CPM assessments and summarizes the findings of neuroimaging studies on the CPM response. The summary includes functional MRI studies assessing CPM responses during scanning as well as functional and structural MRI studies correlating indices with CPM responses assessed outside of the scanner. The findings are discussed in relation to the suggested mechanisms for the CPM response. A better understanding of neural mechanisms underlying spatial processing of nociceptive information could advance both pain research and clinical use of the CPM response as a marker or a treatment target.

Anti- and Pro-Nociceptive mechanisms in neuropathic pain after human spinal cord injury

BACKGROUND

Deficient endogenous pain modulation and increased nociceptive excitability are key features of central sensitization and can be assessed in humans by conditioned pain modulation (CPM, anti-nociceptive) and temporal summation of pain (TSP, pro-nociceptive), respectively. This study aimed to investigate these measures as proxies for central sensitization in subjects with chronic neuropathic pain (NP) after spinal cord injury (SCI).

METHODS

In paraplegic subjects with NP (SCI-NP; n = 17) and healthy controls (HC; n = 17), parallel and sequential sham-controlled CPM paradigms were performed using pressure pain threshold at the hand, that is, above lesion level, as test stimulus. The conditioning stimulus was a noxious cold (verum) or lukewarm water bath (sham) applied contralaterally. Regarding pro-nociceptive mechanisms, a TSP protocol with individually-adjusted pressure pain stimuli at the thenar eminence was used. CPM and TSP magnitudes were related to intensity and spatial extent of spontaneous NP.

RESULTS

Neither the parallel nor sequential sham-controlled CPM paradigm showed any significant inhibition of above-level pressure pain thresholds for SCI-NP or HC. Accordingly, no group difference in CPM capacity was found, however, subjects with more intense spontaneous NP showed lower inhibitory CPM capacity. TSP was observed for both groups but was not enhanced in SCI-NP.

CONCLUSIONS

Our results do not support altered above-level anti- or pro-nociceptive mechanisms in SCI-NP compared with HC; however, they also highlight the relevance of spontaneous NP intensity with regards to the capacity of endogenous pain modulation in SCI subjects.

SIGNIFICANCE

Central sensitization encompasses deficient endogenous pain modulation and increased nociceptive excitability. These two mechanisms can be assessed in humans by conditioned pain modulation and temporal summation of pain, respectively. Our data demonstrates a lack of descending pain inhibition only in subjects with severe neuropathic pain which may hint towards central sensitization at spinal and/or supra-spinal levels. Disentangling the mechanisms of endogenous pain modulation and neuronal hyperexcitability might improve mechanism-based treatment of neuropathic pain in subjects with spinal cord injury.

Virtual Reality as a distraction therapy during cystoscopy: a clinical trial

OBJECTIVES

to investigate whether virtual reality (VR) experience is associated with decreased pain sensation among patients who undergo rigid cystoscopy under local anesthesia.

METHODS

we performed a prospective, randomized, controlled study of 159 patients who were aleatorily enrolled into two groups: VR and control. VR experience intervention consisted of using a headset with a smartphone adapted to a virtual reality glasses where an app-video was played during the procedure. Main outcomes analyzed were pain, discomfort, heart rate variability, difficulty and duration of the cystoscopy. Statistical analyses were performed using a Student's t test, Mann-Whitney test and Chi-square test. A P<0.05 was considered to be statistically significant.

RESULTS

among 159 patients studied (VR group=80 patients; control group=79 patients), the mean age was 63,6 years and 107 (67,3%) were male. There was no statistically significant difference in baseline characteristics between the 2 groups. VR was significantly associated to decreased heart rate variability (6,29 vs 11,09 bpm, P<0,001) and lower duration of the procedure (5,33 vs 8,65 min, P<0,001). Also, when cystoscopies due to double-J extraction were excluded, VR experience was associated with reduced pain on the visual analog score of pain (3,26 vs 4,33 cm, P=0,023).

CONCLUSIONS

the use of VR as a distraction therapy while performing outpatient cystoscopies is safe, has no side effects, is associated with less pain and discomfort, and reduces length of procedure.

Virtual Reality and the Mediation of Acute and Chronic Pain in Adult and Pediatric Populations: Research Developments

The use of virtual reality (VR) in the mediation of acute pain in adults has shown real benefit to patients for the past 20 years. This review of the literature provides a descriptive synthesis of the types of VR technology, the mechanisms by which VR mediates pain, and a history of early research in the area. A review of the use of VR to mediate chronic pain in adults, and both acute and chronic pain in pediatric populations follows. The studies reviewed provide mixed results and it is noted that many studies have small sample sizes, are case studies, and do not control for extraneous variables such as the dosage and type of VR technology used. Although VR is an exciting area of inquiry that promises to yield multiple applications, there is a necessity to conduct larger random controlled trials to better understand the use cases for which VR is most effective.

A Realidade Virtual como terapia de distração durante cistoscopias: um ensaio clínico

RESUMO Objetivos: investigar se a experiência de realidade virtual (RV) está associada à diminuição da dor em pacientes submetidos à cistoscopia rígida sob anestesia local. Métodos: foi realizado um estudo prospectivo, randomizado e controlado de 159 pacientes que foram alocados aleatoriamente em dois grupos: RV e controle. A intervenção da experiência de RV consistiu no uso de óculos de realidade virtual com smartphone adaptado e fones de ouvido, onde um vídeo foi reproduzido durante o procedimento. Os principais desfechos analisados foram dor, desconforto, variabilidade da frequência cardíaca, dificuldade e duração da cistoscopia. As análises estatísticas foram realizadas com o teste t de Student, o teste de Mann-Whitney e o teste do qui-quadrado. Um P<0,05 foi considerado como estatisticamente significativo. Resultados: entre os 159 pacientes estudados (grupo RV=80; grupo controle=79), a média de idade foi 63,6 anos e 107 (67,3%) eram do sexo masculino. Não houve diferença estatisticamente significativa nas características basais entre os grupos. A RV foi significativamente associada à menor variabilidade da frequência cardíaca (6,29 vs 11,09 bpm, P<0,001) e menor duração do procedimento (5,33 vs 8,65 min, P<0,001). Além disso, quando cistoscopias devido à extração de duplo J foram excluídas, a RV foi associada à redução da dor na escala visual analógica (3,26 vs 4,33cm, P=0,023). Conclusões: o uso da RV como terapia de distração durante a realização de cistoscopias ambulatoriais é seguro, não tem efeitos colaterais, está associado a menos dor e desconforto e reduz a duração do procedimento.