High- and low-frequency transcutaneous electrical nerve stimulation does not reduce experimental pain in elderly individuals

Abstract : Despite its widespread clinical use, the efficacy of transcutaneous electrical nerve stimulation (TENS) remains poorly documented in elderly individuals. In this randomized, double-blind crossover study, we compared the efficacy of high-frequency (HF), lowfrequency (LF), and placebo (P) TENS in a group of 15 elderly adults (mean age: 67 6 5 years). The effect of HF-, LF-, and P-TENS was also evaluated in a group of 15 young individuals (26 6 5 years; same study design) to validate the effectiveness of the TENS protocols that were used in the elderly group. Each participant came to the laboratory on 3 separate occasions to receive, in random order, HF-, LF-, and P-TENS. Pain intensity and pain perception thresholds were assessed before, during, and after TENS, using an experimental heat pain paradigm. For the young group, there was a significant decrease in pain intensity during and after HF- and LF-TENS when compared with baseline, with both HF- and LF-TENS being superior to P-TENS. In the older group, HF- and LF-TENS did not reduce pain when compared with baseline and no difference was observed between the 2 active TENS sessions and P-TENS. High-frequency, LF-, and P-TENS all increased pain thresholds in young individuals, whereas in older individuals, only LF-TENS increased pain thresholds. Taken together, these results suggest that TENS is effective in young, but not in older, individuals. Future studies should be conducted to confirm these results in pain populations and to identify strategies that could enhance the effect of TENS in the elderly

Can we improve pain and sleep in elderly individuals with transcranial direct current stimulation? : results from a randomized controlled pilot study

Abstract : Background: The prevalence of chronic pain and sleep disturbances substantially increases with age. Pharmacotherapy remains the primary treatment option for these health issues. However, side effects and drug interactions are difficult to control in elderly individuals. Aims: The objective of this study was to assess the feasibility of conducting a randomized sham-controlled trial and to collect preliminary data on the efficacy of transcranial direct current stimulation (tDCS) to reduce pain and improve sleep in older adults suffering from chronic pain. Methods: Fourteen elderly individuals (mean age 71±7 years) suffering from chronic pain and sleep complaints were randomized to receive either anodal tDCS, applied over the primary motor cortex (2 mA, 20 minutes), or sham tDCS, for 5 consecutive days. Pain was measured with visual analog scales, pain logbooks and questionnaires, while sleep was assessed with actigraphy, sleep diaries and questionnaires. Results: There were no missing data for pain and sleep measures, except for actigraphy, that generated several missing data. Blinding was maintained throughout the study, for both the evaluator and participants. Active but not sham tDCS significantly reduced pain (P or =0.18). Conclusion: The present study provides guidelines for the implementation of future tDCS studies in larger populations of elderly individuals. M1 anodal tDCS in this population appears to be effective to reduce pain, but not to improve sleep

Transcutaneous electrical nerve stimulation (TENS): towards the development of a clinic-friendly method for the evaluation of excitatory and inhibitory pain mechanisms

Abstract: Background: Temporal summation and conditioned pain modulation (CPM) can be measured using a thermode and cold pressor test (CPTest). Unfortunately, these complex and expensive tools are ill-suited for routine clinical assessments. Aims: We aimed to compare the temporal summation and CPM obtained with the thermode + CPTest paradigm to those obtained with a novel paradigm using transcutaneous electrical nerve stimulation (TENS). Methods: We assessed temporal summation and CPM in 29 healthy participants, using two paradigms (random order): TENS, and thermode + CPTest. In the TENS paradigm, both the conditioning stimulus (CS) and the test stimulus (TS) were delivered using TENS; in the thermode + CPTest paradigm, the CS consisted of a CPTest and the TS was delivered using a thermode. We compared the average temporal summation and CPM evoked by the two paradigms. Results: Average temporal summation was similar for both modalities (P = 0.90), and the number of participants showing temporal summation was similar in both paradigms (19 with thermode vs. 18 with TENS; P = 1.00). Average CPM response was larger following the thermode + CPTest than following the TENS (P = 0.005), and more participants showed CPM with the thermode + CPTest paradigm compared to the TENS paradigm (24 vs. 14; P = 0.01). Conclusions: Both paradigms were roughly equivalent in the ability to evoke temporal summation (although response to one modality did not predict response to the other), but the TENS paradigm appeared to be less apt to induce a CPM response than the thermode + CPTest paradigm.Contexte: La sommation temporelle et la modulation de la douleur conditionnée (MDC) peuvent être mesurées à l’aide d’une thermode et d’un test au froid. Malheureusement, ces tests complexes et coûteux sont mal adaptés aux évaluations cliniques de routine. Objectifs: Nous avons cherché à comparer la sommation temporelle et la modulation de la douleur conditionnée obtenues avec le paradigme thermode + test au froid à ceux obtenus avec un nouveau paradigme utilisant la neurostimulation électrique transcutanée (TENS). Méthodes: Nous avons évalué la sommation temporelle et la modulation de la douleur conditionnée chez 29 participants en bonne santé, en utilisant les deux paradigmes (ordre aléatoire) : TENS, et thermode + test au froid. Dans le paradigme TENS, Le stimulus de conditionnement et le stimulus d’essai ont été transmis à l’aide de la neurostimulation électrique transcutanée ; dans le paradigme thermode + test au froid, le stimulus de conditionnement consistait en un test au froid et le stimulus d’essai était transmis à l’aide d’une thermode. Nous avons comparé la sommation temporelle et la modulation de la douleur conditionnée moyennes évoqués par les deux paradigmes. Résultats: La sommation temporelle moyenne était similaire pour les deux modalités (P = 0,90), et le nombre de participants ayant montré une sommation temporelle étaient similaires dans les deux paradigmes (19 avec la thermode contre 18 avec la TENS; P = 1,00). La réponse moyenne de modulation de la douleur conditionnée était plus importante après la thermode + test au froid qu’après la neurostimulation électrique transcutanée (P = 0,005), et un plus grand nombre de participants ont montré une modulation de la douleur conditionnée avec la thermode + test au froid par rapport au paradigme TENS (24 contre 14 ; P = 0,01)

Transcutaneous electrical nerve stimulation and placebo analgesia: is the effect the same for young and older individuals?

Abstract: Purpose: Placebo analgesia refers to a perceived reduction in pain intensity following the administration of a simulated or otherwise medically ineffective treatment. Previous studies have shown that many factors can influence the magnitude of placebo analgesia. However, few investigations have examined the effect of age on placebo analgesia, and none have done it in the context of electrotherapeutic interventions. The objective of this study is to compare the placebo response induced by sham transcutaneous electrical nerve stimulation (TENS) between young and older individuals, using an experimental heat-pain paradigm. Patients and methods: Twenty-two young (21–39 years) and 22 older (58–76 years) healthy adults participated in this comparative study. Experimental heat pain was evoked with a thermode (2-min stimulation at a constant individually adjusted temperature) applied on the lumbar region. Participants were asked to evaluate the intensity of their pain using a computerized visual analog scale. Experimental pain was induced before and after an unconditioned placebo intervention (placebo TENS) applied for 25 min. Results: In young individuals, no significant pain reductions were noted, whereas in older individuals, a statistically significant pain reduction was observed after the placebo stimulation (P,0.01). Between-group analyses revealed that placebo analgesia was greater in older individuals (40% pain reduction) compared with young individuals (15% pain reduction) (P,0.05). However, sham TENS increased heat-pain thresholds in the young group (P,0.01), but not in the older group (P=0.43). Conclusion: Our results indicate that placebo analgesia is influenced by age, with older individuals showing larger placebo analgesia than young adults. Although these results should be confirmed in clinical pain populations, the current observations bear potentially important consequences for the design of future placebo-controlled trials and for healthcare professionals working with elderly patients

Unravelling the effect of experimental pain on the corticomotor system using transcranial magnetic stimulation and electroencephalography.

Abstract : The interaction between pain and the motor system is well-known, with past studies showing that pain can alter corticomotor excitability and have deleterious effects on motor learning. The aim of this study was to better understand the cortical mechanisms underlying the interaction between pain and the motor system. Experimental pain was induced on 19 young and healthy participants using capsaicin cream, applied on the middle volar part of the left forearm. The effect of pain on brain activity and on the corticomotor system was assessed with electroencephalography (EEG) and transcranial magnetic stimulation (TMS), respectively. Compared to baseline, resting state brain activity significantly increased after capsaicin application in the central cuneus (theta frequency), left dorsolateral prefrontal cortex (alpha frequency), and left cuneus and right insula (beta frequency). A pain-evoked increase in the right primary motor cortex (M1) activity was also observed (beta frequency), but only among participants who showed a reduction in corticospinal output (as depicted by TMS recruitment curves). These participants further showed greater beta M1-cuneus connectivity than the other participants. These findings indicate that pain-evoked increases in M1 beta power are intimately tied to changes in the corticospinal system, and provide evidence that beta M1-cuneus connectivity is related to the corticomotor alterations induced by pain. The differential pattern of response observed in our participants suggest that the effect of pain on the motor system is variable from on individual to another; an observation that could have important clinical implications for rehabilitation professionals working with pain patients

Transcranial magnetic stimulation measures in the elderly: reliability, smallest detectable change and the potential influence of lifestyle habits

Background: Transcranial magnetic stimulation (TMS) is a non-invasive technique that can be used to evaluate cortical function and corticospinal pathway in normal and pathological aging. Yet, the metrologic properties of TMS-related measurements is still limited in the aging population. Objectives: The aim of this cross-sectional study was to document the reliability and smallest detectable change of TMS measurements among community-dwelling seniors. A secondary objective was to test if TMS measurements differ between elders based on lifestyle, medical and socio-demographic factors. Methods: Motor evoked potentials (MEPs) elicited by single-pulse TMS were recorded in the first dorsal interosseous (FDI) in 26 elderly individuals (mean age = 70 3.8 years). Resting motor threshold (rMT), MEP amplitudes and contralateral silent period (cSP) were measured on two separate occasions (1-week interval), and the standard error of the measurement (SEMeas), intraclass correlation coefficient (ICC), and smallest detectable change in an individual (SDCindv) were calculated. Lifestyle, medical and socio-demographic factors were collected using questionnaires. TMS-related outcomes were compared using independent sample t-test based on the presence of chronic health diseases, chronic medication intake, obesity, history of smoking, physical activity levels, gender, and level of education. Results: rMT and cSP measures were the most reliable outcomes, with the lowest SEMeas and highest ICCs, whereas MEP amplitude-related measures were less reliable. SDCindv levels were generally high, even for rMT (7.29 %MSO) and cSP (43.16– 50.84 ms) measures. Although not systematically significant, results pointed toward a higher corticospinal excitability in elderly individuals who were regularly active, who had no chronic medical conditions and who did not take any medication. Conclusion: Even though SDCindv levels were relatively high, these results show that rMT and cSP are the most reliable outcomes to investigate age-related changes in the corticomotor system and suggest that the influence of factors such as lifestyle habits and medications on TMS measures should be investigated further

Can we quickly and thoroughly assess pain with the PACSLAC-II? : a convergent validity study in long-term care residents suffering from dementia.

Abstract : A previous study found that the modified version of the Pain Assessment Checklist for Seniors with Limited Ability to Communicate (PACSLAC-II) is a valid tool to assess pain in elderly individuals suffering from dementia and who are unable to communicate verbally. The primary objective of this study was to confirm the convergent validity of the PACSLAC-II using direct evaluation of long-term care residents in real-life situations, using two other well-validated pain assessment scales (i.e., PACSLAC and Pain Assessment in Advanced Dementia [PAINAD]). A secondary objective was to document and compare the time required to complete and score each assessment scale. During two potentially painful procedures (i.e., transfer/mobilization), 46 long-term care residents (mean age = 83 ± 10 years) suffering from dementia were observed by three independent evaluators, each using one of the assessment scales (randomly assigned). Correlational analyses and analysis of variance were used to evaluate the association between each scale and to compare scoring time. The PACSLAC (r = 0.61) and the PAINAD (r = 0.65) were both moderately associated with the PACSLAC-II (all p values < .001). The PAINAD's average scoring time (63 ± 19 seconds) was lower than the PACSLAC-II's (96 ± 2 seconds), which was lower than the PACSLAC's (135 ± 53 seconds) (all p values < .001). These results suggest that the PACSLAC-II is a valid tool for assessing pain in individuals with dementia. The time required to complete and score the PACSLAC-II was reasonable, supporting its usefulness in clinical settings

Understanding the interaction between pain and motor system : an innovative study combining transcranial magnetic stimulation and electroencephalography

Résumé : L’interaction entre la douleur et le système moteur est bien connue en clinique et en réadaptation. Il est sans surprise que la douleur est un phénomène considérablement invalidant, affectant la qualité de vie de ceux et celles qui en souffrent. Toutefois, les bases neurophysiologiques qui sous-tendent cette interaction demeurent, encore aujourd’hui, mal comprises. Le but de la présente étude était de mieux comprendre les mécanismes corticaux impliqués dans l’interaction entre la douleur et le système moteur. Pour ce faire, une douleur expérimentale a été induite à l’aide d’une crème à base de capsaïcine au niveau de l’avant-bras gauche des participants. L'effet de la douleur sur la force des projections corticospinales ainsi que sur l’activité cérébrale a été mesuré à l’aide de la stimulation magnétique transcrânienne (TMS) et de l’électroencéphalographie (EEG), respectivement. L’analyse des données EEG a permis de révéler qu'en présence de douleur aiguë, il y a une augmentation de l’activité cérébrale au niveau du cuneus central (fréquence têta), du cortex dorsolatéral préfrontal gauche (fréquence alpha) ainsi que du cuneus gauche et de l'insula droite (toutes deux fréquence bêta), lorsque comparée à la condition initiale (sans douleur). Également, les analyses démontrent une augmentation de l'activité du cortex moteur primaire droit en présence de douleur, mais seulement chez les participants qui présentaient simultanément une diminution de leur force de projections corticales (mesurée avec la TMS t=4,45, p3.66; all ps<0.01). A pain-evoked increase in the right primary motor cortex (M1) activity was also observed (beta frequency), but only among participants who showed a simultaneous reduction in the strength of the corticospinal projections (quantified using the recruitment curves obtained with TMS; t=4.45, p<0.05). These participants further showed greater beta motor-cuneus connectivity than participants for whom pain did not affect M1 somatotopy (t=3.58, p<0.05). These results suggest that pain-evoked increases in M1 beta power are intimately tied to alterations in corticospinal system. Moreover, we provide evidence that beta motor-cuneus connectivity is related to the corticomotor alterations induced by pain

Assessment of descending nervous system projections: a window to better understand knee osteoarthritis pain?

Introduction: L’arthrose du genou est une pathologie douloureuse caractérisée par des changements ostéoarticulaires. Un nombre grandissant d’études suggèrent que ces changements n’expliquent que partiellement la douleur ressentie par les individus souffrant d’arthrose, et que certains mécanismes inhibiteurs descendants, situés au niveau du système nerveux central, pourraient jouer un rôle clé dans la douleur arthrosique. La présente étude visait donc à évaluer la relation entre les manifestations cliniques liées à l’arthrose du genou (douleur, raideur et incapacité) et les projections descendantes (corticospinales et bulbospinales) issues du système nerveux, en plus d’évaluer la faisabilité d’un devis longitudinal visant à explorer la relation entre ces projections descendantes et l’évolution clinique des patients suivant une arthroplastie du genou. Un troisième objectif était de déterminer la présence d’association entre des mesures de tractographie (imagerie de diffusion) et les symptômes cliniques des patients. Méthode: Vingt-huit patients souffrant d’arthrose du genou, et en attente d’arthroplastie, ont été recrutés. Les projections corticospinales ont été mesurées à l’aide de la stimulation magnétique transcrânienne (TMS), alors que les projections bulbospinales (CPM) ont été évaluées en utilisant une procédure de contre-irritation faisant intervenir des stimulations thermiques. Différents questionnaires ont été utilisés afin de documenter les manifestations cliniques liées à l’arthrose du genou et évaluer certains facteurs psychologiques des participants. Ces mêmes mesures ont été prises de nouveau à 6 mois ainsi qu’à 12 mois post-arthroplastie. Résultats: Tous les participants souffraient de douleur modérée à sévère (score moyen: (4 ± 3)/10). Aucune relation n’a été observée entre les mesures cliniques et les mesures neurophysiologiques (seuil moteur, pente des courbes de recrutement, CPM) traduisant l’intégrité et l’efficacité des projections descendantes (tous les p > 0,06). Néanmoins, l’intensité de la douleur était associée à une excitabilité corticospinale plus élevée à 110% du seuil moteur. La raideur, quant à elle, était corrélée avec l’anisotropie fractionnelle (FA) et la densité de fibre apparente (AFD) de la voie corticospinale de la région d’intérêt (genou). Les participants ont tous complété leur visite de suivi à l’exception de deux individus; dont les raisons de leur abandon n’étaient pas en lien avec les procédures de l’étude. Conclusion: À première vue, les résultats suggèrent que les projections corticospinales et bulbospinales ne seraient pas associées aux manifestations cliniques des individus souffrant d’arthrose du genou. Plusieurs projets de recherche, avec des puissances statistiques adéquates, sont nécessaires afin de tirer des conclusions finales quant à l’impact des projections descendantes dans les manifestations cliniques liées à l’arthrose du genou et l’évolution clinique des patients suite à l’arthroplastie.Abstract: Introduction: Knee osteoarthritis (OA) is a painful condition characterized by osteoarticular changes. A growing number of studies suggest that these changes only partially explain the pain experienced by individuals with OA, and that some of the descending projections of the nervous system, may play an important role in OA pain. The purpose of the current study was to evaluate the relationship between clinical manifestations related to knee OA (pain, stiffness and disability) and the strength of corticospinal and bulbospinal projections, in addition to assessing the feasibility of a longitudinal design exploring the relationship between these descending projections and the clinical evolution of patients following knee arthroplasty. A third objective was to evaluate the association between tractography measures (diffusion imagery) and the clinical symptoms of knee OA patients. Methods: Twenty-eight patients with knee OA awaiting for arthroplasty were recruited. Corticospinal projections were measured using transcranial magnetic stimulation (TMS), while bulbospinal projections (CPM) were evaluated using a counter-irritation paradigm involving thermal stimulations (thermode and cold-water bath). Different questionnaires were used to document the clinical manifestations of knee OA and to evaluate key psychological factors of the participants. These same measures were taken again at 6 and 12 months post-arthroplasty. Results: All participants suffered from moderate to severe pain (mean score: (4 ± 3)/10). No association was observed between measures of pain, stiffness and disability and neurophysiological measures (motor threshold, slope of recruitment curves, CPM) reflecting the strength of the descending projections (all p > 0.06), although, pain intensity was associated with higher corticospinal excitability at 110% of the motor threshold. Diffusion imagery revealed that stiffness was correlated with fractional anisotropy (FA) and apparent fiber density (AFD) of the corticospinal pathway of the region of interest (knee). All participants completed their follow-up visits except for two individuals; their reasons for dropping out were not related to the study procedures. Conclusion: At first sight, the results suggest that the corticospinal and bulbospinal projections are not associated with the clinical manifestations of individuals with knee OA. More research, with adequately powered studies, is essential to draw final conclusions about the impact of descending projections in the clinical manifestations related to knee OA and the clinical evolution of patients following arthroplasty

Understanding the interaction between pain and motor system : an innovative study combining transcranial magnetic stimulation and electroencephalography

Résumé : L’interaction entre la douleur et le système moteur est bien connue en clinique et en réadaptation. Il est sans surprise que la douleur est un phénomène considérablement invalidant, affectant la qualité de vie de ceux et celles qui en souffrent. Toutefois, les bases neurophysiologiques qui sous-tendent cette interaction demeurent, encore aujourd’hui, mal comprises. Le but de la présente étude était de mieux comprendre les mécanismes corticaux impliqués dans l’interaction entre la douleur et le système moteur. Pour ce faire, une douleur expérimentale a été induite à l’aide d’une crème à base de capsaïcine au niveau de l’avant-bras gauche des participants. L'effet de la douleur sur la force des projections corticospinales ainsi que sur l’activité cérébrale a été mesuré à l’aide de la stimulation magnétique transcrânienne (TMS) et de l’électroencéphalographie (EEG), respectivement. L’analyse des données EEG a permis de révéler qu'en présence de douleur aiguë, il y a une augmentation de l’activité cérébrale au niveau du cuneus central (fréquence têta), du cortex dorsolatéral préfrontal gauche (fréquence alpha) ainsi que du cuneus gauche et de l'insula droite (toutes deux fréquence bêta), lorsque comparée à la condition initiale (sans douleur). Également, les analyses démontrent une augmentation de l'activité du cortex moteur primaire droit en présence de douleur, mais seulement chez les participants qui présentaient simultanément une diminution de leur force de projections corticales (mesurée avec la TMS t=4,45, p3.66; all ps<0.01). A pain-evoked increase in the right primary motor cortex (M1) activity was also observed (beta frequency), but only among participants who showed a simultaneous reduction in the strength of the corticospinal projections (quantified using the recruitment curves obtained with TMS; t=4.45, p<0.05). These participants further showed greater beta motor-cuneus connectivity than participants for whom pain did not affect M1 somatotopy (t=3.58, p<0.05). These results suggest that pain-evoked increases in M1 beta power are intimately tied to alterations in corticospinal system. Moreover, we provide evidence that beta motor-cuneus connectivity is related to the corticomotor alterations induced by pain