Ethnic differences regarding tactile and pain thresholds in the trigeminal region

Age differences in pain sensitivity and effect of topical lidocaine on the tongue in healthy female subjects

PURPOSE

To assess the sensitivity and the effect of topical lidocaine on the tongue by quantitative sensory testing, comparing healthy middle-aged female subjects with healthy young female subjects.

METHODS

Sixteen healthy female subjects including eight in their fifties and eight in their twenties participated. They participated in two sessions at a 2-week interval in randomized order: lidocaine (experimental session) or placebo gel (placebo session) was applied on the tongue tip for 5min. The following parameters were taken on the tongue tip before and after application of the gel in each session: tactile detection threshold (TDT), filament-prick pain detection threshold (FPT), and numerical rating scale (NRS).

RESULTS

An increase of both TDT and FPT and a decrease of NRS were found after lidocaine application in both middle-aged and young female subjects. In the elder females, an increase of TDT, FPT, and NRS was also found after placebo gel application. However, the changes were not statistically significant, except for FPT in middle-aged subjects.

CONCLUSION

The reactions found after lidocaine application in middle-aged female subjects could be due to habituation as well as to the post-application effect of placebo gel. Placebo-induced changes appeared more pronounced in the elder females.

Age-, gender- and body site-specific reference values of thermal Quantitative Sensory Testing in the Italian population using the Q-sense device

BACKGROUND

Age-, gender- and body site-specific values of thermal Quantitative Sensory Testing (QST) measures have not yet been reported using the novel and cheap device 'Q-sense'. Here, we aimed to assess normative values of Q-sense-derived parameters in a representative Italian population.

METHODS

QST parameters were measured in 84 healthy participants (42 males; aged 20-76 years) equally distributed into three age groups (18-39, 40-59 and 60-80 years). We explored the Warm and the Cold Detection Thresholds (WDT and CDT, respectively) with the method of limits (MLI) and the method of levels (MLE), and the Heat Pain Threshold (HPT) with the MLI. We tested the trigeminal supraorbital region, the hand thenar, and the foot dorsum on the right body side.

RESULTS

We calculated non-parametric reference limits (2.5-97.5th) according to age, gender and tested site. All QST measures were affected by age, gender and tested site. In the extra-trigeminal body sites, females showed lower WDT and higher CDT, while males had higher HPT. Worse sensory discriminative abilities and increased HPT values were found in people aged over 40 on the foot. Age-related differences were more evident with the reaction time-dependent MLI vs. MLE paradigm.

CONCLUSIONS

Demographic characteristics must be considered when QST is used in the clinical setting. The definition of reference limits for sensory testing with the Q-sense herein provided can pave the way towards a more widespread use of thermal QST for diagnosing small fiber neuropathy and for identifying patients' profiles in different chronic pain syndromes.

Measurement of pressure discomfort threshold in auricular concha for in-ear wearables design

In an effort to mitigate the homogenization of in-ear wearables, designers have been focusing on finding new solutions to enhance user comfort. While the concept of pressure discomfort thresholds (PDT) in humans has been applied to product design, research on the auricular concha remains scarce. In this study, we conducted an experiment to measure the PDT at six points in the auricular concha of 80 participants. Our results showed that the tragus was the most sensitive area and that gender, symmetry, and Body Mass Index (BMI)had no significant effect on PDT. Based on these findings, we generated pressure sensitivity maps of the auricular concha to aid in the optimization of in-ear wearable design.

In-ear earphone design-oriented pressure sensitivity evaluation on the external ear

This study aimed to explore the pressure sensitivity of the external ear that can be the basis for adapting the pressure distribution on the concha for in-ear earphone design. Overall, 30 participants were included in this study, where an electronic mechanical algometer with a stepping motor was used to apply constant pressure. Before the experiment, the customised concha shell models of the participants were positioned in the ear perpendicular to the concha surface. Furthermore, the pressure discomfort threshold (PDT), moderate pressure discomfort (MPD), and maximum pressure threshold (MPT) in eight regions of the ear were recorded. This study's results indicate that the four regions of the external ear are less sensitive to pressure than those of the other regions. Additionally, women had higher pressure sensitivity values in the external ear. Therefore, this study's findings could have important implications for earphone designs and evaluating discomfort conditions in the external ear. Practitioner summary: This study explores the pressure sensitivity threshold (PDT, MPD, and MPT) on the external ear and the relevant implications for in-ear earphone design. Interestingly, regions closer to the bone structure were less sensitive to pressure, and men could tolerate greater pressure on the external ear than women.

Dense 3D pressure discomfort threshold (PDT) map of the human head, face and neck: A new method for mapping human sensitivity

When designing wearables that interface with the human head, face and neck, designers and engineers consider human senses, ergonomics and comfort. A dense 3D pressure discomfort threshold map could be helpful, but does not exist yet. Differences in pressure discomfort threshold for areas of the head, neck and face were recorded, to create a 3D pressure discomfort threshold map. Between 126 and 146 landmarks were placed on the left side of the head, face and neck of twenty-eight healthy participants (gender balanced). The positions of the landmarks were specified using an EEG 10-20 system-based landmark-grid on the head and a self-developed grid on the face and neck. A 3D scan was made to capture the head geometry and landmark coordinates. In a randomised order, pressure was applied on each landmark with a force gauge until the participant indicated experiencing discomfort. By interpolating all collected pressure discomfort thresholds based on their corresponding 3D coordinates, a dense 3D pressure discomfort threshold map was made. A relatively low-pressure discomfort threshold was found in areas around the nose, neck front, mouth, chin-jaw, cheek and cheekbone, possibly due to the proximate or direct location of nerves, blood veins and soft (muscular) tissue. Medium pressure discomfort was found in the neck back, forehead and temple regions. High pressure discomfort threshold was found in the back of the head and scalp, where skin is relatively thin and closely supported by bone, making these regions interesting for mounting or resting head, face and neck related equipment upon.

Surgical experience and different glove wearing conditions affect tactile sensibility

Background

The fingers' tactile sensibility is essential in surgery, especially in microsurgery. Therefore, surgeons seeking to improve their performance often prefer certain glove brands and wearing habits. There is the need of objectively testing these glove wearing conditions and determine the effect of surgical experience with regard to tactile sensibility by comparing surgeons with non-surgeons.

Methods

This cross-sectional single-center pilot-study was conducted between June and August 2021. Two groups of 27 surgeons and 27 non-surgeons underwent two-point-discrimination (2PD) and Semmes-Weinstein monofilament testing (SWMT) of both index fingers with bare hands and with wearing six different brands of surgical gloves. Different wearing conditions, such as single-gloving, double-gloving, well-fitted, under- and oversized gloves, were evaluated within and between the groups.

Results

Most glove types decreased tactile sensibility (2PD and SWMT) of surgeons and non-surgeons. Interestingly, the thinnest gloves showed similar 2PD values to bare hands in both groups. Double-gloving negatively impacted SWMT, without influencing 2PD. Undersized gloves showed better 2PD and SWMT than well-fitted gloves, while oversized gloves showed no tactile drawbacks. With bare hands and certain glove conditions, the surgeons' 2PD and SWMT was significantly better than the non-surgeons', indicating a positive effect of surgical experience on tactile sensibility.

Conclusion

Our study demonstrated the positive impact of surgical experience on tactile sensibility, as demonstrated by the surgeons. The sensibility of the gloved hand varies on the surgical glove type, but favors thinner gloves, single gloving (rather than double gloving) and undersized or well-fitted gloves.

Eliciting national and subnational sets of disability weights in mainland China: Findings from the Chinese disability weight measurement study

BACKGROUND

The disability weight (DW) quantifies the severity of health states from disease sequela and is a pivotal parameter for disease burden calculation. We conducted a national and subnational DW measurement in China.

METHODS

In 2020-2021, we conducted a web-based survey to assess DWs for 206 health states in 31 Chinese provinces targeting health workers via professional networks. We fielded questions of paired comparison (PC) and population health equivalence (PHE). The PC data were analysed by probit regression analysis, and the regression results were anchored by results from the PHE responses on the DW scale between 0 (no loss of health) and 1 (health loss equivalent to death).

FINDINGS

We used PC responses from 468,541 respondents to estimate DWs of health states. Eight of 11 domains of health had significantly negative coefficients in the regression of the difference between Chinese and Global Burden of Disease (GBD) DWs, suggesting lower DW values for health states with mention of these domains in their lay description. We noted considerable heterogeneity within domains, however. After applying these Chinese DWs to the 2019 GBD estimates for China, total years lived with disability (YLDs) increased by 14·9% to 177 million despite lower estimates for musculoskeletal disorders, cardiovascular diseases, mental disorders, diabetes and chronic kidney disease. The lower estimates of YLDs for these conditions were more than offset by higher estimates of common, low-severity conditions.

INTERPRETATION

The differences between the GBD and Chinese DWs suggest that there might be some contextual factors influencing the valuation of health states. While the reduced estimates for mental disorders, alcohol use disorder, and dementia could hint at a culturally different valuation of these conditions in China, the much greater shifts in YLDs from low-severity conditions more likely reflects methodological difficulty to distinguish between health states that vary a little in absolute DW value but a lot in relative terms.

FUNDING

This work was supported by the National Natural Science Foundation of China [grant number 82173626], the National Key Research and Development Program of China [grant numbers 2018YFC1315302], Wuhan Medical Research Program of Joint Fund of Hubei Health Committee [grant number WJ2019H304], and Ningxia Natural Science Foundation Project [grant number 2020AAC03436].

Skin conductance levels and responses in Asian and White participants during fear conditioning✰

Fear conditioning paradigms are frequently used in the translational study of anxiety and fear-related disorders. Accordingly, it is important to understand whether the measurement of fear conditioning responses is systematically influenced by an individual's race. Studies have found increased pain sensitivity and smaller physiological startle responses in Asian individuals, compared to White individuals; to our knowledge, no studies have evaluated whether skin conductance response (SCR) outcomes differ between Asian and White individuals. In a series of secondary data analyses, we investigated potential differences in skin conductance level (SCL), orienting SCR, unconditioned SCR, SCR to CS+ and CS-, differential SCR, and differential SCR non-responder status. In sample 1, Asian participants (n = 97) demonstrated a significantly smaller mean differential SCR compared to White participants (n = 86). No other between group differences were observed. In sample 2, there was no difference in mean differential SCR between Asian (n = 52) and White (n = 62) participants, although more Asian participants failed to show adequate skin conductance levels for study entry. To our knowledge, this is the first study to evaluate differences between Asian and White samples using skin conductance outcomes in a fear conditioning paradigm. We detected only subtle evidence for SCR differences between Asian and White samples, unlikely to reach significance outside large studies.

Personal influencing factors for pressure pain threshold in healthy people: A systematic review and meta-analysis

All studies that investigated personal factors influencing pressure pain threshold (PPT) in healthy people were synthesized. Data was summarized, and risk of bias (RoB) and level of evidence were determined. Results were pooled per influencing factor, grouped by body region and included in meta-analyses. Fifty-four studies were eligible. Five had low, nine moderate, and 40 high RoB. Following meta-analyses, a strong conclusion was found for the influence of scapular position, a moderate for the influence of gender, and a weak for the influence of age (shoulder/arm region) and blood pressure on PPT. In addition, body mass index, gender (leg region), alcohol consumption and pain vigilance may not influence PPT. Based on qualitative summary, depression and menopause may not influence PPT. For other variables there was only preliminary or conflicting evidence. However, caution is advised, since the majority of included studies showed a high RoB and several were not eligible to include in meta-analyses. Heterogeneity was high in the performed meta-analyses, and most conclusions were weak. More standardized research is necessary.

Do patient-reported measures of disease activity in rheumatoid arthritis vary between countries? Results from a Nordic collaboration

OBJECTIVES

To investigate whether patient-reported outcomes vary across countries and are influenced by cultural/contextual factors. Specifically, we aimed to assess inter-country differences in tender joint count (TJC), pain and patient's global health assessment (PGA), and their impact on disease activity (DAS28-CRP) in RA patients from five Nordic countries.

METHODS

We collected data (baseline, 3- and 12-months) from rheumatology registers in the five countries comprising RA patients starting a first ever MTX or a first ever TNF inhibitor (TNFi). In order to assess the role of context (=country), we separately modelled TJC, pain and PGA as functions of objective variables (CRP, swollen joint count, age, sex, calendar period and disease duration) with linear models. Analyses were performed at each time point and for both treatments. We further assessed the impact of inter-country differences on DAS28-CRP.

RESULTS

A total of 27 645 RA patients started MTX and 19 733 started a TNFi. Crude inter-country differences at MTX start amounted to up to 4 points (28 points scale) for TJC, 10 and 27 points (0-100 scale) for pain and PGA, respectively. Corresponding numbers at TNFi start were 3 (TJC), 27 (pain) and 24 (PGA) points. All differences were reduced at 3- and 12-months, and attenuated when adjusting for the objective variables. The variation in predicted DAS28-CRP across countries amounted to <0.5 units.

CONCLUSIONS

Inter-country differences in TJC, pain and PGA are greater than expected based on differences in objective measures, but have a small clinical impact on DAS28-CRP across countries.

Effect of cross-cultural differences on thickness, firmness and sweetness sensitivity

Sensitivity of the somatosensory system may be influenced by multiple physiological parameters. Variations in oral physiology can arise from cross-cultural differences which may potentially affect sensory sensitivity. The aim of this case study was to quantify texture and taste sensitivity in Dutch (Caucasian) and Chinese (Asian) adults living in the Netherlands. Eighty-five healthy subjects were recruited including 44 Dutch (Caucasian) adults (29 females, 22.8 ± 2.3 yrs) and 41 Chinese (Asian) adults (30 females, 24.5 ± 2.1 yrs) living in the Netherlands for less than 1 year. Three sets of stimuli were used to quantify sensitivity of thickness (maltodextrin solutions differing in viscosity), firmness (agar gels differing in fracture stress) and sweetness (sucrose solutions differing in concentration). The 2-Alternative Forced Choice (2-AFC) ascending staircase method was used to determine texture and taste sensitivity. Unstimulated and stimulated saliva flow rate, fungiform papillae density (FPD), lingual tactile threshold and PROP taster status were determined and are referred to as physiological and sensory consumer characteristics. No significant differences were observed between Chinese and Dutch adults for thickness (Dutch 2.60 mPas, Chinese 2.19 mPas), firmness (Dutch 10.5 kPa, Chinese 10.3 kPa) and sweetness sensitivity (Dutch 0.012 g/mL, Chinese 0.017 g/mL). No significant differences were observed between Chinese and Dutch adults for saliva flow rate, lingual tactile threshold and PROP taster status. The relationships between the three sensory sensitivities (thickness, firmness, sweetness) and five physiological and sensory consumer characteristics (unstimulated and stimulated saliva flow rate, FPD, lingual tactile threshold, PROP taster status) were analyzed. Only one out of 15 relationships, firmness sensitivity and FPD, was significantly and weakly related suggesting that inter-individual variation in these consumer characteristics is almost unrelated to sensory sensitivity. We conclude that in this case study thickness, firmness and sweetness sensitivities do not differ between Dutch and Chinese adults living in the Netherlands. Saliva flow rate, fungiform papillae density, lingual tactile threshold and PROP taster status do not explain inter-individual variation in sensory sensitivity between these consumers.

Assessment of pressure sensitivity in the head region for Chinese adults

Measurement of pressure threshold has found its applications in the fields of medical sciences and product design. Hence it has been a profound area of research interest for several decades. However, hardly any detailed investigation has been undertaken to measure the pressure threshold in the head region. In this study, Pressure Discomfort Threshold (PDT) and Pressure Pain Threshold (PPT) were measured for two hundred eighteen healthy Chinese adults at seventy-six anatomical locations, and further statistical analyses were performed on the acquired data to understand the relationship between different demographic parameters. The results suggest that the pressure sensitivity is low in the vertex region, moderate in the forehead and temporal area, and high in the facial and nasal region. From this study, pressure sensitivity maps were developed for PDT and PPT for Chinese adults. The measured pressure threshold data showed no significant relationship with age and Body Mass Index (BMI).

A randomized non-inferiority pilot study on the use of methoxyflurane (Penthrox®) for pain control in the emergency department

Background:

Patients commonly visit the emergency department for pain after musculoskeletal injury, but the problem of oligoanalgesia is prevalent. Methoxyflurane (Penthrox®) is an inhalational analgesic for moderate to severe trauma-associated pain in stable and conscious patients. It is a fast-acting, effective analgesic that can be readily administered via a non-invasive route, making it an attractive agent for managing acute pain in the emergency departments.

Objectives:

The aim was to assess the analgesic efficacy of methoxyflurane in patients with acute traumatic pain by comparing it to ketorolac, a standard analgesic treatment for moderate pain in emergency departments in Hong Kong.

Methods:

This was a single-center, open-label, randomized controlled, parallel-group, non-inferiority pilot study that enrolled adult patients with moderate trauma-associated pain in an emergency department in Hong Kong. Patients were randomized 1:1 to the methoxyflurane group or the ketorolac group. The primary outcome was the change in pain intensity measured by visual analogue scale from baseline to 5, 15, 30, and 60 min after drug administration.

Results:

Twenty patients received methoxyflurane, and twenty patients received ketorolac. There were significant reductions in pain score over 60 min in both groups. The pain reduction at 5 min was significantly greater for the methoxyflurane group (−13.912 mm; 95% confidence interval = −20.008 to −7.817) than for the ketorolac group (−4.888 mm; 95% confidence interval = −10.983 to 1.208), with the treatment effect (−9.025 mm; 95% confidence interval = −17.656 to −0.393; p = 0.041) demonstrating superiority of methoxyflurane. The treatment effect at 15 and 30 min demonstrated non-inferiority of methoxyflurane versus ketorolac.

Conclusion:

Methoxyflurane provided non-inferior analgesia in the first 30 min with a faster onset of action when compared with ketorolac in moderate traumatic pain. It can be considered a non-invasive, rapid-acting, and effective first-line alternative to currently available analgesics for traumatic pain in emergency settings.

Two-point discrimination assessment of the lower extremities of healthy young Turkish individuals

OBJECTIVES

To investigate the normative two-point discrimination (TPD) values of the lower extremities of healthy young Turkish individuals.

PATIENTS AND METHODS

Fifty-five healthy, young adults were recruited in this prospective study. Ten lower extremity parts were tested with esthesiometer: proximal thigh, midlateral thigh, midmedial thigh, midposterior thigh, proximal lateral leg, distal lateral leg, medial leg, the tip of great toe, skin over 1-2 metatarsal interspace, skin over 5th metatars at both dominant and non-dominant sides.

RESULTS

There were 27 (49.1%) female and 28 (50.9%) male participants with a mean age of 22.06 ± 1.76 years. The reference values of the TPD of the lower extremities were between 42.4 ± 5.4 mm and 4.0 ± 1.3 mm by females and between 42.6 ± 6.4 mm and 4.4 ± 2.4 mm by males. Test values in the combined group of men and women were statistically greater at the dominant sides than the non-dominant sides at the following areas: proximal lateral leg (p = 0.01), distal lateral leg (p = 0.046), medial leg (p = 0.001), tip of great toe (p = 0.02), skin over 1-2 metatarsal interspace (p = 0.010), skin over 5th metatars (p = 0.002). There was no statistical difference in the test scores of men and women in any of the measured areas, with additional evaluation of both the dominant and the non-dominant sides (p > 0.05).

CONCLUSION

The results of the present study demonstrated that TPD ability varied in different skin areas within the same individual. We found that laterality, though with lower scores on the non-dominant side in some lower extremity parts, but not the gender had an effect on TPD.

How do Japanese rate the severity of different diseases and injuries?-an assessment of disability weights for 231 health states by 37,318 Japanese respondents

Background

Disability weights (DWs) are weight factors that reflect the severity of health states for estimates of disability-adjusted life years. A new set of global DWs was published for the Global Burden of Diseases and Injuries (GBD) 2013 study, which relied on sampling from various world regions, but included little data for countries in East Asia. This study aimed to measure DWs in Japan using comparable methods, and compare the results with previous estimates from the GBD 2013 DW study.

Methods

We conducted a web-based survey in 2019 to estimate DWs for 231 health states for the Japanese population. The survey included five new health states but otherwise followed the method of the GBD DW measurement study. The survey consisted of 15 paired comparison (PC) questions and 3 population health equivalence questions (PHE) per respondent. We analyzed PC data using probit regression and rescaled results to DW units between 0 (equivalent to full health) and 1 (equivalent to death).

Findings

We considered 37,318 nationally representative respondents. The values of the resulting DWs ranged from 0.707 (95% uncertainty interval (UI) 0.527–0.842) for spinal cord injury at neck level (untreated) to 0.004 (UI 0.001–0.009) for mild anemia. High correlation between Japanese DW and GBD 2013 DW was observed, but there was considerable disagreement. Out of 226 comparable health states, 55 (24.3%) showed more than a factor-of-two difference, of which 41 (74.6%) had a higher value in Japanese DW. Many of the health states with higher DW in the Japan study were injuries, including amputation and fracture, and hearing and vision loss, while mental, behavioral, and substance use disorders generally tended to be lower.

Conclusions

This study has created an empirical basis for assessment of Japanese DWs of health status. The findings from this study based on the Japanese population suggest that there might be contextual differences in rating the severity of health states compared to previous surveys conducted elsewhere.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12963-021-00253-4.

The Adaptation of Pain Assessment Tools from High-Income to Low- and Middle-Income Countries: Psychometric Properties of a Set of Chronic Pain Questionnaires in Mongolian and New Zealand Patient Samples

OBJECTIVE

Chronic pain is a leading cause of disability in low- and middle-income countries; however, pain assessment tools have generally been developed and validated in high-income countries. This study examines the psychometric properties of a set of translated pain (and distress) questionnaires in Mongolia and documents the characteristics of people seeking treatment for chronic pain in Mongolia, compared with those in New Zealand, which is representative of high-income countries.

DESIGN

Cross-sectional, observational.

SETTING

Hospital-based pain treatment centers in New Zealand and Mongolia.

SUBJECTS

People seeking treatment for chronic pain in Mongolia (N = 142) and New Zealand (N = 159).

METHODS

The Brief Pain Inventory, the Depression Anxiety Stress Scale-21, the Pain Catastrophizing Scale, and the Pain Self-Efficacy Questionnaire were translated into Mongolian and administered to patients attending a hospital-based pain service. Questionnaires that were completed by patients in New Zealand were used for comparisons. Internal reliability, convergent validity, and factor structure were assessed in both groups.

RESULTS

Patients in Mongolia were older and reported lower pain intensity, interference, and distress and higher pain self-efficacy than those in New Zealand. The translated questionnaires had good internal consistencies, and the relationships between pain variables were similar across both groups. The factor structure for the Pain Catastrophizing Scale was consistent across both groups, but this was not the case for the Brief Pain Inventory or the Depression Anxiety Stress Scale-21.

CONCLUSIONS

Findings indicate that some pain outcome measures may be appropriate for use in Mongolia and should be investigated in other low- and middle-income countries.

An Objective Pain Score for Chronic Pain Clinic Patients

Objectives

Although numerous studies have looked at the numeric rating scale (NRS) in chronic pain patients and several studies have evaluated objective pain scales, no known studies have assessed an objective pain scale for use in the evaluation of adult chronic pain patients in the outpatient setting. Subjective scales require patients to convert a subjective feeling into a quantitative number. Meanwhile, objective pain scales utilize, for the most part, the patient's behavioral component as observed by the provider in addition to the patient's subjective perception of pain. This study aims to examine the reliability and validity of an objective Chronic Pain Behavioral Pain Scale for Adults (CBPS) as compared to the traditional NRS.

Methods

In this cross-sectional study, patients were assessed before and after an interventional pain procedure by a researcher and a nurse using the CBPS and the NRS. Interrater reliability, concurrent validity, and construct validity were analyzed.

Results

Interrater reliability revealed a fair-good agreement between the nurse's and researcher's CBPS scores, weighted kappa values of 0.59 and 0.65, preprocedure and postprocedure, respectively. Concurrent validity showed low positive correlation for the preprocedure measurements, 0.34 (95% CI 0.16-0.50) and 0.47 (95% CI 0.31-0.61), and moderate positive correlation for the postprocedure measurements, 0.68 (95% CI 0.56-0.77) and 0.67 (95% CI 0.55-0.77), for the nurses and researchers, respectively. Construct validity demonstrated an equally average significant reduction in pain from preprocedure to postprocedure, CBPS and NRS median (IQR) scores preprocedure (4 (2-6) and 6 (4-8)) and postprocedure (1 (0-2) and 3 (0-5)), p < 0.001. Discussion. The CBPS has been shown to have interrater reliability, concurrent validity, and construct validity. However, further testing is needed to show its potential benefits over other pain scales and its effectiveness in treating patients with chronic pain over a long-term. This study was registered with ClinicalTrial.gov with National Clinical Trial Number NCT02882971.

Unilateral, Alloplastic Temporomandibular Joint Reconstruction, Biomechanically What Happens to the Contralateral Temporomandibular Joint?-A Prospective Cohort Study

PURPOSE

Unilateral alloplastic total temporomandibular joint reconstruction (TMJR) might influence the contralateral side joint function. This study's purpose was to estimate the risk for contralateral TMJR and the jaw function of the contralateral untreated temporomandibular joint (TMJ).

PATIENTS AND METHODS

A prospective cohort study design was used for patients who underwent unilateral alloplastic TMJR. The primary predictor was time after TMJR, and the secondary predictors were pre-TMJR mandibular angle resection, prior ipsilateral TMJ surgeries, and TMJR design (custom, stock). The primary outcome variable was the need for contralateral TMJR. The secondary outcome variables were the results of jaw function-jaw tracking, maximum voluntary clenching, surface electromyography, and pressure pain thresholds (PPT) and patient's quality-of-life (oral health-related quality-of-life [OHrQoL]). Data were collected preoperatively (T0), and 1 year (T1), 2-3 years (T2), and ≥ 4 years postoperatively (T4). Analysis of variance with post hoc Tukey -HSD test and multiple linear regression analysis were used for statistical analysis. P < .05 was considered significant.

RESULTS

Thirty-nine patients were enrolled, 15 males and 24 females, with an average age of 48.9 ± 16.2 years. Two patients (5.1%) required a contralateral TMJR. Contralateral condylar motion, incisal laterotrusion, and protrusion slightly decreased, while incisal opening (P = .003), rotation angle (P = .013), opening deflection, surface electromyography activity, maximum voluntary clenching (P = .01), PPTs, and OHrQoL all increased. Pre-TMJR mandibular angle resection had an impact on PPTs and subjective outcomes and prior ipsilateral TMJ surgeries on the opening rotation angle.

CONCLUSIONS

Based on this study, bilateral TMJR does not appear necessary when the contralateral TMJ is healthy. Unilateral alloplastic TMJR is associated with improved contralateral jaw function and OHrQoL.

Attenuating Pain With the Past: Nostalgia Reduces Physical Pain

Previous work has found that nostalgia, a sentimental longing for the past, is associated with psychological, emotional, and social benefits. Recent research has demonstrated that nostalgic reflection also can improve individuals’ physical health (i.e., exercise) and reduce temperature-related pain. Building on this, two experiments examined how nostalgia can reduce people’s pain perceptions (i.e., reduced severity and increased tolerance). Specifically, Study 1 showed that inducing nostalgia through a writing task decreased perceived pain severity (i.e., intensity) among self-reported chronic pain sufferers. Study 2, in turn, demonstrated that Japanese individuals experienced increased pain tolerance (i.e., the maximum level of pain a person can tolerate) for a pressure algometer task following thoughts of nostalgia (vs. a control prime). This work provides evidence that nostalgic reflection may serve as a psychological resource to reduce the perceived severity of physical pain.

Assessing peripheral fibers, pain sensitivity, central sensitization, and descending inhibition in Native Americans: main findings from the Oklahoma Study of Native American Pain Risk

Native Americans (NAs) have a higher prevalence of chronic pain than other U.S. racial/ethnic groups, but there have been few attempts to understand the mechanisms of this pain disparity. This study used a comprehensive battery of laboratory tasks to assess peripheral fiber function (cool/warm detection thresholds), pain sensitivity (eg, thresholds/tolerances), central sensitization (eg, temporal summation), and pain inhibition (conditioned pain modulation) in healthy, pain-free adults (N = 155 NAs, N = 150 non-Hispanic Whites [NHWs]). Multiple pain stimulus modalities were used (eg, cold, heat, pressure, ischemic, and electric), and subjective (eg, pain ratings and pain tolerance) and physiological (eg, nociceptive flexion reflex) outcomes were measured. There were no group differences on any measure, except that NAs had lower cold-pressor pain thresholds and tolerances, indicating greater pain sensitivity than NHWs. These findings suggest that there are no group differences between healthy NAs and NHWs on peripheral fiber function, central sensitization, or central pain inhibition, but NAs may have greater sensitivity to cold pain. Future studies are needed to examine potential within-group factors that might contribute to NA pain risk.

Pain-related anxiety promotes pronociceptive processes in Native Americans: bootstrapped mediation analyses from the Oklahoma Study of Native American Pain Risk

INTRODUCTION

Evidence suggests Native Americans (NAs) experience higher rates of chronic pain than the general US population, but the mechanisms contributing to this disparity are poorly understood. Recently, we conducted a study of healthy, pain-free NAs (n = 155), and non-Hispanic whites (NHWs, n = 150) to address this issue and found little evidence that NAs and NHWs differ in pain processing (assessed from multiple quantitative sensory tests). However, NAs reported higher levels of pain-related anxiety during many of the tasks.

OBJECTIVE

The current study is a secondary analysis of those data to examine whether pain-related anxiety could promote pronociceptive processes in NAs to put them at chronic pain risk.

METHODS

Bootstrapped indirect effect tests were conducted to examine whether pain-related anxiety mediated the relationships between race (NHW vs NA) and measures of pain tolerance (electric, heat, ischemia, and cold pressor), temporal summation of pain and the nociceptive flexion reflex (NFR), and conditioned pain modulation of pain/NFR.

RESULTS

Pain-related anxiety mediated the relationships between NA race and pain tolerance and conditioned pain modulation of NFR. Exploratory analyses failed to show that race moderated relationships between pain-related anxiety and pain outcomes.

CONCLUSION

These findings imply that pain-related anxiety is not a unique mechanism of pain risk for NAs, but that the greater tendency to experience pain-related anxiety by NAs impairs their ability to engage descending inhibition of spinal nociception and decreases their pain tolerance (more so than NHWs). Thus, pain-related anxiety may promote pronociceptive processes in NAs to place them at risk for future chronic pain.

Sex differences in pain and opioid mediated antinociception: Modulatory role of gonadal hormones

Sex-related differences in pain and opioids has been the focus of many researches. It is demonstrated that women experience greater clinical pain, lower pain threshold and tolerance, more sensitivity and distress to experimentally induced pain compared to men. Sex differences in response to opioid treatment revealed inconsistent results. However, the etiology of these disparities is not fully elucidated. It is, therefore, conceivable now that this literature merits to be revisited comprehensively. Possible multifaceted factors seem to be associated. These include neuroanatomical, hormonal, neuroimmunological, psychological, social and cultural aspects and comorbidities. This review aims at providing an overview of the substantial literature documenting the sex differences in pain and analgesic response to opioids from animal and human studies within the context of the modulatory effects of the aforementioned factors. A detailed and critical discussion of the cellular and molecular signaling pathways underlying the modulatory actions of gonadal hormones in the sexual dimorphism in pain processing and opioid analgesia is extensively presented. It is indicated that sexual dimorphic activation of certain brain regions contributes to differential pain sensitivity between females and males. Plausible crosstalk between sex hormones and neuroimmunological signaling pertinent to toll-like and purinergic receptors is uncovered as causal cues underlying sexually dimorphic pain and opioid analgesia. Conceivably, a thorough understanding of these factors may aid in sex-related advancement in pain therapeutic management.

The safety and preventive effects of a supraorbital transcutaneous stimulator in Japanese migraine patients

Cefaly (Cefaly Technology, Seraing, Belgium) is a device that stimulates the bilateral supraorbital nerve transcutaneously. A previous study in Europe proved that Cefaly was an effective and safe device as a preventive therapy for migraine. However, there have been no studies on this device in Asia. We examined the safety and preventive effect of Cefaly for migraine. One-hundred patients were prospectively collected from four headache units in Japan. The inclusion criteria were as follows: 18–75 years of age, migraine with and without aura, and at least 2 attacks per month. A 4-week baseline period was followed by 12-week treatment period. The primary end point was the change from baseline in the number of migraine days at 12 weeks. The secondary end points include the changes of the number of migraine attacks, all headache days, acute medicine consumption days and headache severity. After treatment, a questionnaire survey on the satisfaction of the treatment was administered to the patients. The Friedmann test was used to assess the changes between baseline period and after treatment, and Mann-Whitney U test was used for the comparison of efficacy between chronic migraine and episodic migraine, with and without prophylactic treatment or medication overuse. After 12 weeks of treatment, Cefaly use significantly decreased the number of migraine days (8.16 vs. 6.84; p = 0.0036). Only three subjects (3.0%) dropped out due to the adverse effects; however, no serious adverse events were observed. The compliance of this study was very high at 90.0%. Furthermore, a significant decrease was observed in the number of migraine attacks (5.33 vs. 3.94; p = 0.0002) and the intake of acute antimigraine drugs (8.75 vs. 7.83; p = 0.0166). Cefaly is considered to be a safe and highly tolerable effective device for Japanese patients. Trial registration: This study was retrospectively registered to UMIN-CTR(UMIN000033333) on 10 July 2018.

Mechanical sensitivity and psychological factors in patients with burning mouth syndrome

OBJECTIVES

The aim of this study was to compare mechanical sensitivity on the tongue using quantitative sensory testing (QST) and psychological factors using the General Health Questionnaire (GHQ) between burning mouth syndrome (BMS) patients and healthy participants.

MATERIALS AND METHODS

Participants comprised 20 female BMS patients (68.1 ± 7.4 years) and 20 healthy females (65.4 ± 4.6 years). Psychological factors were evaluated with GHQ. Tactile detection thresholds (TDT) and filament-prick pain detection thresholds (FPT) were used to evaluate mechanical sensitivity on the tongue in all participants. TDT and FPT were measured on the tongue within both the painful area and the non-painful area in BMS patients, and on the tongue on both sides in healthy participants. As controls, TDT and FPT were measured with Semmes-Weinstein monofilaments on the skin of the mentum and palm in all participants.

RESULTS

GHQ scores were significantly higher in BMS patients than in healthy participants (P = 0.024). No significant differences in TDT or FPT on the tongue, mentum, or palm were seen between BMS patients and healthy participants (P > 0.05). BMS patients showed no significant differences in TDT or FPT between the painful and non-painful areas on the tongue (P > 0.05). There were no significant correlations among TDT/FPT and GHQ score in BMS patients (P > 0.05).

CONCLUSIONS

These findings could indicate a more important role for psychological factors than mechanical sensitivity in BMS pathophysiology.

CLINICAL RELEVANCE

Pain on the tongue in elderly female patients with BMS may be more related to psychological factors.

Swearing as a response to pain: A cross-cultural comparison of British and Japanese participants

BACKGROUND AND AIMS

Research suggests swearing can moderate pain perception. The present study assessed whether changes in pain perception due to swearing reflect a "scripting" effect by comparing swearing as a response to pain in native English and Japanese speakers. Cognitive psychology denotes a 'script' to be a sequence of learnt behaviours expected for given situations. Japanese participants were included as they rarely, if ever, swear as a response to pain and therefore do not possess an available script for swearing in the context of pain. It was hypothesised that Japanese participants would demonstrate less tolerance and more sensitivity to pain than English participants, and - due to a lack of an available script of swearing in response to pain - that Japanese participants would not experience swearword mediated hypoalgesia.

METHODS

Fifty-six native English (mean age=23 years) and 39 Japanese (mean age=21) speakers completed a cold-pressor task whilst repeating either a swear on control word. A 2 (culture; Japanese, British)×2 (word; swear; non-swear) design explored whether Japanese participants showed the same increase in pain tolerance and experienced similar levels of perceived pain when a swearing intervention was used as British participants. Pain tolerance was assessed by the number of seconds participants could endure of cold-pressor exposure and self-report pain measurements. Levels of perceived pain were assessed using a 120-mm horizontal visual analogue scale anchored by descriptors in the participant's native language of "no pain" (left) and "terrible pain" (right). The participant was asked to mark a 10mm vertical line to indicate overall pain intensity. The score was measured from the zero anchor to the participant's mark.

RESULTS

Japanese participants reported higher levels of pain (p<0.005) and displayed lower pain tolerance than British participants (p<0.05). Pain tolerance increased in swearers regardless of cultural background (p<0.001) and no interaction was found between word group and culture (p=0.96), thereby suggesting that swearing had no differential effect related to the cultural group of the participant.

CONCLUSIONS

The results replicate previous findings that swearing increases pain tolerance and that individuals from an Asian ethnic background experience greater levels of perceived pain than those from a Caucasian ethnic background. However, these results do not support the idea of pain perception modification due to a "scripting" effect. This is evidenced as swearword mediated hypoalgesia occurs irrespective of participant cultural background. Rather, it is suggested that modulation of pain perception may occur through activation of descending inhibitory neural pain mechanisms.

IMPLICATIONS

As swearing can increase pain tolerance in both Japanese and British people, it may be suggested that swearword mediated hypoalgesia is a universal phenomenon that transcends socio-cultural learnt behaviours. Furthermore, swearing could be encouraged as an intervention to help people cope with acute painful stimuli.

Pain in amaXhosa women living with HIV/AIDS: a cross-sectional study of ambulant outpatients

Background

Pain is one of the most commonly reported symptoms in people living with HIV/AIDS, whether or not they are receiving anti-retroviral therapy. A recent systematic review identified a paucity of studies exploring pain in women in low and middle income countries. The prevalence and characteristics of pain in women living with HIV/AIDS may differ from that of men as many chronic pain conditions are more prevalent in women. The aims of this study were to establish pain prevalence, characteristics and management in amaXhosa women living with HIV/AIDS. In addition, we aimed to identify whether there were associations between pain in this population and the psychosocial factors of employment, education, self-efficacy, depression, post-traumatic stress disorder, health related quality of life and childhood trauma.

Methods

A cross-sectional study of 229 women who had undergone HIV testing and were registered patients at a community health centre was conducted. Data were collected by interview with a demographic questionnaire, the Brief Pain Inventory-Xhosa, Childhood Trauma Questionnaire–Xhosa, Harvard Trauma Questionnaire–Xhosa for PTSD, Self-Efficacy for Managing Chronic Disease 6-Item Scale-Xhosa; the EQ-5D health related quality of life instrument, and the Beck Depression Inventory.

Results

170 of the women had pain, a prevalence rate of 74.24% (95%CI 68.2 – 79.47%). The women reported significant pain with pain severity of 5.06 ± 1.57 and pain interference of 6.39 ± 1.96 out of 10. Only two women were receiving adequate pain management according to the pain management index. Participants reported a mean of 2.42 ± 1.21 different anatomical sites of pain. There were more unemployed participants in the group with pain and they had significantly fewer years of schooling. Those with pain had lower self-efficacy; health related quality of life and increased depression and PTSD symptom severity.

Conclusion

This study highlights that pain is a common problem for amaXhosa women living with HIV/AIDS. These data emphasise the need to prioritise pain assessment and management in amaXhosa women living with HIV/AIDS. Routinely assessing for the presence of pain in women with HIV/AIDS has the potential to improve pain management and minimise the impact of pain on function.

Age and race effects on pain sensitivity and modulation among middle-aged and older adults

This study tested the effects of aging and race on responses to noxious stimuli using a wide range of stimulus modalities. The participants were 53 non-Hispanic blacks and 138 non-Hispanic white adults, ages 45 to 76 years. The participants completed a single 3-hour sensory testing session where responses to thermal, mechanical, and cold stimuli were assessed. The results suggest that there are selected age differences, with the older group less sensitive to warm and painful heat stimuli than middle-aged participants, particularly at the knee. This site effect supports the hypothesis that the greatest decrement in pain sensitivity associated with aging occurs in the lower extremities. In addition, there were several instances where age and race effects were compounded, resulting in greater race differences in pain sensitivity among the older participants. Overall, the data suggest that previously reported race differences in pain sensitivity emerged in our older samples, and this study contributes new findings in that these differences may increase with age in non-Hispanic blacks for temporal summation and both heat and cold immersion tolerance. We have added to the aging and pain literature by reporting several small to moderate differences in responses to heat stimuli between middle- and older-age adults.

PERSPECTIVE

This study found that the greatest decline in pain sensitivity with aging occurs in the lower extremities. In addition, race differences in pain sensitivity observed in younger adults were also found in our older sample.

An improvement of mechanical pain sensitivity measurement method: the smaller sized probes may detect heterogeneous sensory threshold in healthy male subjects

OBJECTIVE

On the basis of our experience in the application of the mechanical algometer and a number of pilot experiments, we speculated that 0.1- and 0.01-cm(2) probes might improve the measurement of mechanical pain sensitivity relative to the conventional 1-cm(2) probe. Here, we examined the accuracy, feasibility, and applicability of these probes in detecting the mechanical pain sensitivity.

DESIGN

Mechanical pain threshold and tolerance tests were performed on subjects using the three probes of 1, 0.1, and 0.01 cm(2) in random order. We compared the application of these probes.

SETTING

The study was set at the Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

SUBJECTS

Fifty healthy male Han Chinese subjects were recruited.

OUTCOME MEASURES

We compared the qualities of stimulus-evoked pain, test stability, the measuring time, the subjects' acceptance level of the procedure, the validity of pain measurement, and the arduousness of the task for the investigator among the three different size probes.

RESULTS

Compared with the conventional 1-cm(2) probe, the 0.01- and 0.1-cm(2) probes resulted in the subjects responding to stimulus-evoked pain more quickly, accurately, and consistently, and also made the measurement more comfortable for investigators. Up to 80% of the subjects reported the pain quality as a pricking sensation when the 0.01-cm(2) probe was used.

CONCLUSION

The use of the 0.1-cm(2) probe might be more suitable as an optimized method for the detection of pressure pain sensitivity in clinical studies. In addition, the 0.01-cm(2) probe could potentially serve as an alternative to the weighted needle pinprick, providing continuous quantizing detection for pricking pain sensitivity.

Ethnic differences in physical pain sensitivity: role of acculturation

Although research suggests that Asian Americans are more reactive to physical pain than European Americans, some evidence suggests that the observed differences in ethnicity may actually reflect Asian Americans' differing levels of acculturation. Two studies were conducted to test this hypothesis. In Study 1, first- and second-generation Asian Americans and European Americans took part in a cold pressor task. Evidence of heightened pain responses was found only among first-generation Asian Americans. Study 2 further controlled for ethnicity and replicated this pattern in finding heightened pain reactions among mainland Chinese students in Hong Kong relative to Hong Kong Chinese students. These findings suggest a role for acculturation in accounting for ethnic differences in physical pain sensitivity.

Sensibility and taste alterations after impacted lower third molar extractions. A prospective cohort study

Objectives: To determine the incidence, severity and duration of lingual tactile and gustatory function impairments after lower third molar removal. Study Design: Prospective cohort study with intra-subject measures of 16 patients undergoing lower third molar extractions. Sensibility and gustatory functions were evaluated in each subject preoperatively, one week and one month after the extraction, using Semmes-Weinstein monofilaments and 5 different concentrations of NaCl, respectively. Additionally, all patients filled a questionnaire to assess subjective perceptions. Results: Although patients did not perceive any sensibility impairments, a statistically significant decrease was detected when Semmes-Weinstein monofilaments. This alteration was present at one week after the surgical procedure and fully recovered one month after the extraction. There were no variations regarding the gustatory function. Conclusions: Lower third molar removal under local anesthesia may cause light lingual sensibility impairment. Most of these alterations remain undetected to patients. These lingual nerve injuries are present one week after the extraction and recover one month after surgery. The taste seems to remain unaffected after these procedures.

Key words:Lingual nerve, third molar, nerve injury, paresthesia, surgical extraction

Ethnic differences in pain and pain management

Considerable evidence demonstrates substantial ethnic disparities in the prevalence, treatment, progression and outcomes of pain-related conditions. Elucidating the mechanisms underlying these group differences is of crucial importance in reducing and eliminating disparities in the pain experience. Over recent years, accumulating evidence has identified a variety of processes, from neurophysiological factors to structural elements of the healthcare system, that may contribute to shaping individual differences in pain. For example, the experience of pain differentially activates stress-related physiological responses across various ethnic groups, members of different ethnic groups appear to use differing coping strategies in managing pain complaints, providers' treatment decisions vary as a function of patient ethnicity and pharmacies in predominantly minority neighborhoods are far less likely to stock potent analgesics. These diverse factors, and others may all play a role in facilitating elevated levels of pain-related suffering among individuals from ethnic minority backgrounds. Here, we present a brief, nonexhaustive review of the recent literature and potential physiological and sociocultural mechanisms underlying these ethnic group disparities in pain outcomes.

A quantitative review of ethnic group differences in experimental pain response: do biology, psychology, and culture matter?

OBJECTIVE

Pain is a subjectively complex and universal experience. We examine research investigating ethnic group differences in experimental pain response and factors contributing to group differences.

METHOD

We conducted a systematic literature review and analysis of studies using experimental pain stimuli to assess pain sensitivity across multiple ethnic groups. Our search covered the period from 1944 to 2011, and used the PubMed bibliographic database; a reference source containing over 17 million citations. We calculated effect sizes; identified ethnic/racial group categories, pain stimuli, and measures; and examined findings regarding biopsychosociocultural factors contributing to ethnic/racial group differences.

RESULTS

We found 472 studies investigating ethnic group differences and pain. Twenty-six of these met our review inclusion criteria of investigating ethnic group differences in experimental pain. The majority of studies included comparisons between African Americans (AA) and non-Hispanic Whites (NHW). There were consistently moderate to large effect sizes for pain tolerance across multiple stimulus modalities; AA demonstrated lower pain tolerance. For pain threshold, findings were generally in the same direction, but effect sizes were small to moderate across ethnic groups. Limited data were available for suprathreshold pain ratings. A subset of studies comparing NHW and other ethnic groups showed a variable range of effect sizes for pain threshold and tolerance.

CONCLUSION

There are potentially important ethnic/racial group differences in experimental pain perception. Elucidating ethnic group differences has translational merit for culturally competent clinical care and for addressing and reducing pain treatment disparities among ethnically/racially diverse groups.

A systematic literature review of 10 years of research on sex/gender and experimental pain perception - part 1: are there really differences between women and men?

The purpose of this systematic review was to summarize and critically appraise the results of 10 years of human laboratory research on pain and sex/gender. An electronic search strategy was designed by a medical librarian and conducted in multiple databases. A total of 172 articles published between 1998 and 2008 were retrieved, analyzed, and synthesized. The first set of results (122 articles), which is presented in this paper, examined sex difference in the perception of laboratory-induced thermal, pressure, ischemic, muscle, electrical, chemical, and visceral pain in healthy subjects. This review suggests that females (F) and males (M) have comparable thresholds for cold and ischemic pain, while pressure pain thresholds are lower in F than M. There is strong evidence that F tolerate less thermal (heat, cold) and pressure pain than M but it is not the case for tolerance to ischemic pain, which is comparable in both sexes. The majority of the studies that measured pain intensity and unpleasantness showed no sex difference in many pain modalities. In summary, 10 years of laboratory research have not been successful in producing a clear and consistent pattern of sex differences in human pain sensitivity, even with the use of deep, tonic, long-lasting stimuli, which are known to better mimic clinical pain. Whether laboratory studies in healthy subjects are the best paradigm to investigate sex differences in pain perception is open to question and should be discussed with a view to enhancing the clinical relevance of these experiments and developing new research avenues.

Organization of hyperactive microglial cells in trigeminal spinal subnucleus caudalis and upper cervical spinal cord associated with orofacial neuropathic pain

The aim of this study was to evaluate spatial organization of hyperactive microglial cells in trigeminal spinal subnucleus caudalis (Vc) and upper cervical spinal cord (C1), and to clarify the involvement in mechanisms underlying orofacial secondary hyperalgesia following infraorbital nerve injury. We found that the head-withdrawal threshold to non-noxious mechanical stimulation of the maxillary whisker pad skin was significantly reduced in chronic constriction injury of the infraorbital nerve (ION-CCI) rats from day 1 to day 14 after ION-CCI. On day 3 after ION-CCI, mechanical allodynia was obvious in the orofacial skin areas innervated by the 1st and 3rd branches of the trigeminal nerve as well as the 2nd branch area. Hyperactive microglial cells in Vc and C1 were observed on days 3 and 7 after ION-CCI. On day 3 after ION-CCI, a large number of phosphorylated extracellular signal-regulated kinase (pERK)-immunoreactive (IR) cells were observed in Vc and C1. Many hyperactive microglial cells were also distributed over a wide area of Vc and C1 innervated by the trigeminal nerve. The intraperitoneal administration of minocycline significantly reduced the activation of microglial cells and the number of pERK-IR cells in Vc and C1, and also significantly attenuated the development of mechanical allodynia. Furthermore, enhanced background activity and mechanical evoked responses of Vc wide dynamic range neurons in ION-CCI rats were significantly reversed following minocycline administration. These findings suggest that activation of microglial cells over a wide area of Vc and C1 is involved in the enhancement of Vc and C1 neuronal excitability in the early period after ION-CCI, resulting in the neuropathic pain in orofacial areas innervated by the injured as well as uninjured nerves.

Involvement of peripheral ionotropic glutamate receptors in orofacial thermal hyperalgesia in rats

Background

The purpose of the present study was to elucidate the mechanisms that may underlie the sensitization of trigeminal spinal subnucleus caudalis (Vc) and upper cervical spinal cord (C1-C2) neurons to heat or cold stimulation of the orofacial region following glutamate (Glu) injection.

Results

Glu application to the tongue or whisker pad skin caused an enhancement of head-withdrawal reflex and extracellular signal-regulated kinase (ERK) phosphorylation in Vc-C2 neurons. Head-withdrawal reflex and ERK phosphorylation were also enhanced following cold stimulation of the tongue but not whisker pad skin in Glu-injected rats, and the head-withdrawal reflex and ERK phosphorylation were enhanced following heat stimulation of the tongue or whisker pad skin. The enhanced head-withdrawal reflex and ERK phosphorylation after heat stimulation of the tongue or whisker pad skin, and those following cold stimulation of the tongue but not whisker pad skin were suppressed following ionotropic glutamate receptor antagonists administration into the tongue or whisker pad skin. Furthermore, intrathecal administration of MEK1/2 inhibitor PD98059 caused significant suppression of enhanced head-withdrawal reflex in Glu-injected rats, heat head-withdrawal reflex in the rats with Glu injection into the tongue or whisker pad skin and cold head-withdrawal reflex in the rats with Glu injection into the tongue.

Conclusions

The present findings suggest that peripheral Glu receptor mechanisms may contribute to cold hyperalgesia in the tongue but not in the facial skin, and also contribute to heat hyperalgesia in the tongue and facial skin, and that the mitogen-activated protein kinase cascade in Vc-C2 neurons may be involved in these Glu-evoked hyperalgesic effects.

Asians differ from non-Hispanic Whites in experimental pain sensitivity

This study examined differences between Asians and non-Hispanic Whites (Whites) in pain sensitivity, and its relationship to mean arterial pressure (MAP) and heart rate (HR). In 30 Whites (50% female) and 30 Asians (50% female), experimental pain sensitivity was assessed with a hand cold pressor task, yielding measures of pain threshold, tolerance, intensity, and unpleasantness. Mean arterial pressure and HR measurements taken at rest and in response to speech stress were assessed. Perceived stress, anxiety, perfectionism, parental criticism, parental expectations and depressive symptoms were also measured. The results indicated that for the cold pain test, Asians demonstrated significantly lower pain threshold and tolerance levels than Whites. Although no ethnic differences were seen for MAP or HR responses to stress, for Whites higher stress MAP levels were correlated with reduced pain sensitivity, while for Asians higher baseline and stress HR levels were correlated with reduced pain sensitivity. Asians reported higher parental expectations and greater parental criticism than Whites. For Asians only, higher levels of perfectionism were related to more depressive symptoms, anxiety and perceived stress. These results indicate that Asian Americans are more sensitive to experimental pain than Whites and suggest ethnic differences in endogenous pain regulatory mechanisms (e.g. MAP and HR). The results may also have implications for understanding ethnic differences in clinical pain.

Guidelines and recommendations for assessment of somatosensory function in oro-facial pain conditions--a taskforce report

The goals of an international taskforce on somatosensory testing established by the Special Interest Group of Oro-facial Pain (SIG-OFP) under the International Association for the Study of Pain (IASP) were to (i) review the literature concerning assessment of somatosensory function in the oro-facial region in terms of techniques and test performance, (ii) provide guidelines for comprehensive and screening examination procedures, and (iii) give recommendations for future development of somatosensory testing specifically in the oro-facial region. Numerous qualitative and quantitative psychophysical techniques have been proposed and used in the description of oro-facial somatosensory function. The selection of technique includes time considerations because the most reliable and accurate methods require multiple repetitions of stimuli. Multiple-stimulus modalities (mechanical, thermal, electrical, chemical) have been applied to study oro-facial somatosensory function. A battery of different test stimuli is needed to obtain comprehensive information about the functional integrity of the various types of afferent nerve fibres. Based on the available literature, the German Neuropathic Pain Network test battery appears suitable for the study of somatosensory function within the oro-facial area as it is based on a wide variety of both qualitative and quantitative assessments of all cutaneous somatosensory modalities. Furthermore, these protocols have been thoroughly described and tested on multiple sites including the facial skin and intra-oral mucosa. Standardisation of both comprehensive and screening examination techniques is likely to improve the diagnostic accuracy and facilitate the understanding of neural mechanisms and somatosensory changes in different oro-facial pain conditions and may help to guide management.

Comparisons of catastrophizing, pain attitudes, and cold-pressor pain experience between Chinese and European Canadian young adults

Experimental pain research indicates ethnic differences in pain experience. Most of the cross-cultural pain research studied African Americans and Hispanics with little data available for Asian groups. This study examined differences in pain catastrophizing, pain attitudes, and pain responses between Chinese and European Canadian young adults. Prior to completing a cold-pressor (CP) task, 80 Chinese and 80 European Canadian undergraduate students were administered measures of pain catastrophizing and pain attitudes, including stoicism and cautiousness. Pain threshold, pain tolerance, and pain intensity were measured during the CP task. The Short Form-McGill Pain Questionnaire was administered immediately postimmersion to measure sensory and affective pain. While there was no group difference in pain threshold and pain intensity, Chinese participants displayed lower pain tolerance and reported higher SF-MPQ-Affective than European Canadians. Regarding psychological variables, there was no difference in stoicism and cautiousness between groups, but Chinese participants reported greater pain catastrophizing. Mediational analysis indicated that pain catastrophizing mediated the group differences in SF-MPQ-Affective score. The implications of the findings and future research were discussed.

PERSPECTIVE

The study found ethnic differences in cold-pressor responses, in which Chinese undergraduates reported higher levels of pain compared to their Euro-Canadian counterparts. The finding that pain catastrophizing mediated the ethnic difference in SF-MPQ-Affective scores indicated the importance of examining the role of catastrophizing in pain reports from Chinese and Euro-Canadian patients.

Sex, gender, and pain: a review of recent clinical and experimental findings

Sex-related influences on pain and analgesia have become a topic of tremendous scientific and clinical interest, especially in the last 10 to 15 years. Members of our research group published reviews of this literature more than a decade ago, and the intervening time period has witnessed robust growth in research regarding sex, gender, and pain. Therefore, it seems timely to revisit this literature. Abundant evidence from recent epidemiologic studies clearly demonstrates that women are at substantially greater risk for many clinical pain conditions, and there is some suggestion that postoperative and procedural pain may be more severe among women than men. Consistent with our previous reviews, current human findings regarding sex differences in experimental pain indicate greater pain sensitivity among females compared with males for most pain modalities, including more recently implemented clinically relevant pain models such as temporal summation of pain and intramuscular injection of algesic substances. The evidence regarding sex differences in laboratory measures of endogenous pain modulation is mixed, as are findings from studies using functional brain imaging to ascertain sex differences in pain-related cerebral activation. Also inconsistent are findings regarding sex differences in responses to pharmacologic and non-pharmacologic pain treatments. The article concludes with a discussion of potential biopsychosocial mechanisms that may underlie sex differences in pain, and considerations for future research are discussed.

PERSPECTIVE

This article reviews the recent literature regarding sex, gender, and pain. The growing body of evidence that has accumulated in the past 10 to 15 years continues to indicate substantial sex differences in clinical and experimental pain responses, and some evidence suggests that pain treatment responses may differ for women versus men.

Neuroimaging the genomics of pain processing--a perspective

The significant inter-individual variability in pain behavior and its contributing factors remains a pervasive clinical challenge and has generated intense scientific investigations in this field. Recent studies indicate that our genes considerably influence nociceptive information processes, how our nociceptive system copes with peripheral injury, and the individual response to analgesic treatments. Neuroimaging studies of pain are beginning to link such genetic influences with physiological processes in the human brain. This review presents the pioneering endeavors of the hybrid approach of neuroimaging pain genes in humans and identifies potential future directions.