Ethnic differences in oro-facial somatosensory profiles-quantitative sensory testing in Chinese and Danes

Effect of Lingual Nerve Block and Localised Somatosensory Abnormalities in Patients With Burning Mouth Syndrome-A Randomised Crossover Double-Blind Trial

AIMS

To investigate the effect of a lingual nerve block on spontaneous pain in patients with burning mouth syndrome (BMS) and to estimate associated somatosensory abnormalities by quantitative sensory testing (QST).

PROTOCOL AND METHODS

A standardised QST battery including cold detection threshold (CDT), warmth detection threshold (WDT), thermal sensory limen (TSL), paradoxical heat sensation (PHS), cold pain threshold (CPT), heat pain threshold (HPT), mechanical pain threshold (MPT), wind-up ratio (WUR) and pressure pain threshold (PPT) was performed at the oral mucosa of the most painful site and intraoral control site in 20 BMS patients, and at the tongue and cheek mucosa in 22 age- and gender-matched healthy controls. The effect of a lingual nerve block on spontaneous burning pain reported by the BMS patients on a 0-10 cm visual analogue scale (VAS) was investigated in a randomised double-blind crossover design using (1 mL) lidocaine (lido) or saline (sal) with an interval of 1 week. The BMS patients were grouped into 'central' and 'peripheral' mechanisms based on the effect of the lingual nerve injections. For each BMS patient, Z-scores and Loss/Gain scores were computed. Differences among groups and sites were analysed using a two-way ANOVA. Differences within group were assessed by paired t-test.

RESULTS

The 20 BMS patients were characterised on the basis of VAS changes (ΔLido-ΔSal) as a peripheral BMS subgroup (n = 9) with pain relief more than 1 cm on the VAS and a central BMS subgroup (n = 11) with pain relief less than 1 cm. BMS patients (n = 20) had lower sensitivity to thermal stimuli (i.e., CDT, WDT, TSL, CPT, HPT and PPT) and higher sensitivity to mechanical stimuli (i.e., PPT) compared with controls (p ≤ 0.007). Based on Loss/Gain coding, L1G0 (loss of thermal somatosensory function with no somatosensory gain, 55.0%) was the most frequent coding in the BMS group, which was higher than 11.4% in the control group (p < 0.001). Surprisingly, there was no significant difference between the peripheral and central BMS subgroups with regard to the Z-scores of any of the nine QST parameters (p > 0.097).

CONCLUSIONS

The results of the lingual nerve blocks demonstrated two distinct phenotypes with either peripheral or central mechanisms but no direct impact on somatosensory function. Overall, somatosensory function in BMS patients seems abnormal in the painful areas compared to matched controls with a conspicuous loss of thermosensory function.

Conditioned Pain Modulation Differences in Central and Peripheral Burning Mouth Syndrome (BMS) Patients

AIM

To evaluate conditioned pain modulation (CPM) in burning mouth syndrome (BMS) patients with different pain mechanisms.

MATERIALS AND METHODS

Twenty BMS patients (52.0 ± 6.8 years, 17 women and 3 men) and age- and gender-matched 22 healthy controls were enrolled in this randomised controlled trial. The patients received an active lingual nerve block (lidocaine) and a placebo injection (saline) randomly with an interval of 1 week in a double-blinded manner. Patients evaluated their pain intensity on a 0- to 10-cm visual analogue scale (VAS) before and after each injection, with or without CPM. Based on the anaesthesia effect, BMS patients were divided into two groups with presumed different pain mechanisms; a 'central subgroup (n = 11)' with pain relief less than 1 cm and 'peripheral subgroup (n = 9)' with pain relief more than 1 cm on the VAS. Mechanical pain threshold (MPT) and wind-up ratio (WUR) were investigated at two oral mucosa regions: the region with most intense symptoms and a control region for the patient group; tongue and buccal region for the control group. CPM was induced by immersing the left hand into cold water. A moderate level of pain (around five on the VAS) was obtained by adjusting the water temperature. MPT and WUR were measured twice for all the participants with and without CPM, which was analysed and presented as relative change in MPT and WUR. Differences between groups were analysed using two-way ANOVA. Differences within group between tests were assessed by paired t-test.

RESULTS

At baseline, there were no significant group differences for MPT or WUR between BMS patients and healthy controls (p ≥ 0.156). The mean bath temperature to evoke moderate pain for the BMS group was significantly lower than that for the healthy control group (8.9°C vs. 11.9°C, p = 0.003). The CPM evoked an inhibitory modulation in 18.2%-44.4% of BMS patients, while for the healthy group, the ratio was 68.2%-81.8%. Central BMS patients had smaller CPM effects than healthy participants at the painful site and control site, which indicated a decreased CPM function (p ≤ 0.034). Peripheral BMS patients had lower CPM effects than healthy participants only at the painful site (p = 0.037).

CONCLUSIONS

The present findings documented impairment of central nociceptive inhibition processing in BMS patients which was more extensive in central BMS than peripheral BMS. These findings add to the suggestion that BMS may a heterogeneous pain condition with at least two different phenotypes.

Recovery of the Infraorbital Nerve Following Open Reduction and Fixation Surgery of Zygomaticomaxillary Complex Fractures-A Prospective Cohort Study Based on Quantitative Sensory Testing

This study aimed to assess the sensory function of the infraorbital nerve in patients with fractures of the zygomatic complex who underwent open reduction and internal fixation at different time points using quantitative sensory testing, which was established by the German Neuropathic Pain Research Network, comprising a 7-item mechanical and thermal sensory test. A total of 21 patients (age range 17-46 y, 14 males) with unilateral zygomatic complex fractures were included. Quantitative sensory testing was conducted before the operation and at 1 week, 3 months, and 6 months operatively, with cold detection threshold, warmth detection threshold, cold pain threshold, heat pain threshold, mechanical detection threshold, mechanical pain threshold, pressure pain threshold, and vibration detection threshold being measured in bilateral infraorbital regions. Notable changes in sensitivity were observed in all values except for the mechanical pain threshold. In the majority of patients with zygomaticomaxillary complex fractures, infraorbital hypoesthesia was significantly improved within 3 months postoperatively, and almost complete recovery could be achieved by 6 months postoperatively.

Visual psychosocial profiling of Chinese temporomandibular disorder pain patients and correlations with somatosensory function

BACKGROUND

Psychosocial function of Chinese temporomandibular disorders (TMD) pain patients and the correlation with somatosensory function has not been sufficiently studied.

OBJECTIVE

The study aims at assessing the psychosocial function of Chinese TMD pain patients by visualisation method and evaluating the correlations with somatosensory function quantitatively.

METHODS

The Symptom Checklist 90 (SCL-90) questionnaire and standardised quantitative sensory testing (QST) were administered to 70 Chinese TMD pain patients and age- and gender-matched healthy controls (HCs). Of these, 40 TMD arthralgia patients received QST before and after medication. Psychosocial and somatosensory parameters were transformed into standardised scores. Differences within groups were assessed through t tests. Correlations between psychosocial and somatosensory profiles were explored through correlation analyses with Bonferroni correction for multiple comparisons.

RESULTS

100% of the Chinese TMD pain patients exhibited psychosocial distress in contrast to HCs. Anger and hostility showed negative correlation with the thermal nonnociceptive parameter (thermal sensory limen, p =.002) and nociceptive parameters (cold pain threshold and pain pressure threshold, p<.001). Correlation analysis indicated that cold detection threshold was negatively correlated with somatization and mechanical pain sensitivity had a negative correlation with anger and hostility through medical treatment (p <.001).

CONCLUSIONS

Visual psychosocial profiles provided an easy overview of psychosocial function in Chinese TMD pain patients. Anger and hostility was associated with increased thermal nonnociceptive and nociceptive sensitivity to stimuli. Psychosocial distress might be negatively associated with TMD treatment response which indicated a possible need for psychological intervention during treatment.

The normative values of pain thresholds in healthy Taiwanese

OBJECTIVE

Quantitative sensory testing is widely used in clinical and research settings to assess the sensory functions of healthy subjects and patients. It is of importance to establish normative values in a healthy population to provide reference for studies involving patients. Given the absence of normative values for pain thresholds in Taiwan, the aim of this study was to report the normative values for future reference in the Taiwanese population and compare the differences between male and female participants.

METHODS

Healthy adults without any chronic or acute pain condition were recruited. The pain thresholds were assessed over the cephalic (supraorbital area and masseter muscle) and extracephalic (medio-volar forearm and thenar eminence) areas. The heat, cold, mechanical punctate, and pressure pain thresholds were measured with a standardized protocol. Comparisons between male and female participants were performed.

RESULTS

One hundred and thirty healthy participants (55 males: 30.4 ± 7.4 years; 75 females: 30.5 ± 8.1 years) finished the assessments. Male participants were less sensitive to mechanical stimuli, including pressure over masseter muscle (male vs. female: 178.5 ± 56.7 vs. 156.6 ± 58.4 kPa, p = .034) and punctate over medio-volar forearm (male vs. female: 116.4 ± 45.2 vs. 98.7 ± 65.4 g, p = .011), compared to female participants. However, female participants were less sensitive to cold stimuli, indicated by lower cold pain thresholds over the supraorbital area (male vs. female: 18.6 ± 8.4 vs. 13.6 ± 9.3°C, p = .004), compared to male participants. No significant differences were found between sexes in other pain threshold parameters.

CONCLUSIONS

We provided the normative values of healthy male and female adults in Taiwan. This information is crucial for comparison in future pain-related studies to identify potential hypoalgesia or hyperalgesia of tested subjects.

Secondary analysis: heat and self-report pain sensitivity associate with biological sex and racialized sociocultural group but may not be mediated by anxiety or pain catastrophizing

Introduction

Previous studies have demonstrated associations between sex and racialized group on pain sensitivity and tolerance. We analyzed the association of sex and racialized group on heat pain sensitivity, sensibility to painful suprathreshold mechanical pain (STMP), and pain sensitivity questionnaire (PSQ). We hypothesized that anxiety and pain catastrophizing reported by racialized minority groups and women would mediate enhanced pain sensitivity. Our secondary aim was to evaluate validity of the PSQ in a diverse population.

Methods

Using quantitative sensory testing for painful heat, STMP (forces: 64, 128, 256, and 512 mN), and PSQ, we evaluated pain sensitivity in 134 healthy participants [34 (18 women) Asian, 25 (13 women) Black, and 75 (41 women) White]. We used general linear and linear mixed models to analyze outcomes. We assessed mediation of state and trait anxiety and pain catastrophizing on pain sensitivity.

Results

Racialized minority status was associated with greater heat pain sensitivity (F = 7.63; P = 0.00074) and PSQ scores (F = 15.45; P = 9.84 × 10-7) but not associated with STMP (F = 1.50; P = 0.23). Female sex was associated with greater heat pain sensitivity (F = 4.9; P = 0.029) and lower PSQ (F = 9.50; P = 0.0025) but not associated with STMP (F = 0.0018; P = 0.97). Neither anxiety nor pain catastrophizing mediated associations between sex or racialized group with heat pain threshold or PSQ. Differential experience of individual items (F = 19.87; P = 3.28 × 10-8) limited PSQ face validity in racialized minorities.

Conclusion

Consistent with previous research, sensitivity to painful heat was associated with racialized minority status and female sex. By contrast, there was no significant effect of racialized minority status or female sex on STMP. Some PSQ items are inapplicable to participants from racialized minority groups.

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.

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.

Bite Force, Occlusal Contact and Pain in Orthodontic Patients during Fixed-Appliance Treatment

Previously, bite force, occlusal contact and pain were investigated in orthodontic patients with moderate-to-severe malocclusion, but not in patients with minor malocclusion. The purpose of this study was to investigate changes in bite force, teeth in occlusal contact and pain in orthodontic patients with minor crowding before orthodontic treatment (T0), after bonding (T1), during treatment (T2), post-treatment (T3) and during retention (T4). In total, 27 patients (21 females, 6 males, median age 15.3 years) with neutral occlusion and normal craniofacial morphology were treated with non-extractions and fixed appliances. Differences in the registered data were analysed by a mixed linear model with repeated measures. Bite force and teeth in occlusal contact significantly decreased between T0 and T1 (p < 0.0001, respectively) and between T0 and T2 (p < 0.01, respectively). Bite force and teeth in occlusal contact significantly increased between T1 and T4 (p < 0.05, p < 0.0001, p < 0.001, respectively) and between T2 and T4 (p < 0.05, p < 0.0001, p < 0.01, respectively). No significant difference in pain was found. The results indicate that bite force and teeth in occlusal contact significantly decreased during treatment and reached baseline level at retention. The findings may prove valuable for informing orthodontic patients with minor malocclusion.

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.

Increased somatosensory amplification is associated with decreased pressure pain thresholds at both trigeminal and extra-trigeminal locations in healthy individuals

BACKGROUND

The diagnosis of temporomandibular disorders (TMD) is based on patient history and physical examination, and may require medical imaging. Masticatory muscle palpation is essential to make a diagnosis of TMD. However, the response of masticatory muscles to mechanical pressure stimuli depends on many physical and psychological factors.

OBJECTIVE

This study aimed at determining the impact of somatosensory amplification (SSA)-an estimate of somatic awareness and bodily hypervigilance-on pressure pain thresholds (PPTs) measured at both trigeminal and extra-trigeminal locations in healthy individuals.

METHODS

PPTs were measured at the right anterior temporalis and superficial masseter, and the thenar eminence of the right hand in one hundred healhty individuals (69F, 31M), divided in three groups based on their SSA scores: low (N = 32), intermediate (N = 34) and high (N = 34). General linear models were used to test between-group differences in PPTs including sex as a covariate. The level of significance was set at P < .05.

RESULTS

Individuals with high SSA had lower PPTs at the anterior temporalis than individuals with low (P = .006) and intermediate (P = .001) SSA. No significant between-group differences were found in PPTs measured at the masseter (P = .372). PPTs measured at the thenar eminence were significantly lower in the high than the low SSA group (P = .009). Females had lower PPTs at the masseter than males (P = .021) but not at other muscle locations (all P > .05).

CONCLUSION

Increased somatosensory amplification is associated with decreased pressure pain thresholds at both trigeminal and extra-trigeminal locations in healthy individuals. SSA could be a potential confounder while diagnosing TMD and evaluating treatment outcomes.

Orofacial quantitative sensory testing: Current evidence and future perspectives

BACKGROUND AND OBJECTIVE

Orofacial quantitative sensory testing (QST) is an increasingly valuable psychophysical tool for evaluating neurosensory disorders of the orofacial region. Here, we aimed to evaluate the current evidence regarding this testing method and to discuss its future clinical potential.

DATA TREATMENT

We conducted a literature search in Medline, Embase and Scopus for English-language articles published between 1990 and 2019. The utilized search terms included QST, quantitative, sensory testing and neurosensory, which were combined using the AND operator with the terms facial, orofacial, trigeminal, intraoral and oral.

RESULTS

Our findings highlighted many methods for conducting QST-including method of levels, method of limits and mapping. Potential stimuli also vary, and can include mechanical or thermal stimulation, vibration or pinprick stimuli. Orofacial QST may be helpful in revealing disease pathways and can be used for patient stratification to validate the use of neurosensory profile-specific treatment options. QST is reportedly reliable in longitudinal studies and is thus a candidate for measuring changes over time. One disadvantage of QST is the substantial time required; however, further methodological refinements and the combination of partial aspects of the full QST battery with other tests and imaging methods should result in improvement.

CONCLUSIONS

Overall, orofacial QST is a reliable testing method for diagnosing pathological neurosensory conditions and assessing normal neurosensory function. Despite the remaining challenges that hinder the use of QST for everyday clinical decisions and clinical trials, we expect that future improvements will allow its implementation in routine practice.

Assessment of somatosensory changes in Chinese temporomandibular disorders arthralgia patients by quantitative sensory testing

BACKGROUND

Somatosensory changes in Chinese temporomandibular disorders (TMD) arthralgia patients have not been fully studied by the latest technologies.

OBJECTIVE

This study aims at assessing somatosensory changes in Chinese TMD arthralgia patients quantitatively.

METHODS

Standardised quantitative sensory testing (QST) was performed on the pain sites and contralateral sites of 40 patients diagnosed with TMD arthralgia according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) before and after medication; similar measures were taken in 40 age- and gender-matched healthy controls. Differences within and between groups were assessed through Z-scores, two-way ANOVA and loss/gain coding system.

RESULTS

The pain sites of patients presented increased sensitivity to thermal stimuli and mechanical pain stimuli together with decreased sensitivity to mechanical tactile stimuli before medication (P < .001). Before treatment, 100% of patients had somatosensory abnormalities at the pain sites; the most frequent abnormalities were somatosensory gain to cold nociceptive, pinprick and pressure stimuli, and the most frequent loss/gain score was L0G3 (no somatosensory loss with a gain of thermal and mechanical somatosensory function; 70.0%). After treatment, although the clinical symptoms and signs of 40 patients disappeared, 80.0% of the patients' pain sites still showed multiple phenotype abnormalities. The most frequent loss/gain score was L0G2 (no somatosensory loss with a gain of mechanical somatosensory function; 35.0%).

CONCLUSIONS

Multiple phenotypes of facial somatosensory abnormalities were detected in Chinese TMD arthralgia patients before and after treatment, despite the disappearance of clinical signs and symptoms. Individual variations indicate a possible need for subgroup classification, individualised management and mechanism-based treatment.

Somatosensory changes in Chinese patients after coronectomy vs. total extraction of mandibular third molar: a prospective study

Objectives

This study aimed to quantitatively compare the somatosensory function changes of inferior alveolar nerve (IAN) after mandibular third molar extraction with a surgery protocol of coronectomy, as opposed to the conventional method.

Materials and methods

Patients with a lower third molar directly contacting IAN were recruited and assigned either to a test group (coronectomy group) or a control group (conventional extraction). A standardized quantitative sensory testing (QST) battery was performed for four times: one week before surgery and the second, seventh, and 28th days after surgery. Z-scores and the loss/gain coding system were applied for each participant.

Results

A total of 140 molars (test group: n = 91, control group: n = 49) were enrolled. The sensitivity of the mechanical detection threshold (MDT) and pressure pain threshold (PPT) significantly increased after surgery more than before surgery in both groups (P ≤ 0.001). After the surgery, the sensitivities of the cold detection threshold (CDT), cold pain threshold (CPT), and heat pain threshold (HPT) were significantly higher in the test group than in the control group (P ≤ 0.027). The risk of IANI was significantly larger (P = 0.041) in the test group than in the control group.

Conclusions

QST was a sensitive way to detect somatosensory abnormalities even with no subjective complaint caused by surgery. Coronectomy had less influence on IAN function than conventional total extraction.

Clinical relevance

The somatosensory function changes after mandibular third molar extraction were quantitatively studied, and coronectomy was proved a reliable alternation to reduce IAN injury rate.

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.

Disrupted offset analgesia distinguishes patients with chronic pain from healthy controls

Offset analgesia (OA) represents a disproportionately large decrease of pain perception after a brief, temporary increment of thermal pain stimulus and was reported attenuated in patients with neuropathic pain. We examined whether OA depends on the increment duration before offset, and whether individual features of OA distinguish patients with chronic pain and healthy controls. We used a Peltier-type thermal stimulator and OA paradigms including 5-, 10-, or 15-s duration of 1°C-increment (T2) over 45°C. We first examined OA response, on the left volar forearm, at 3 different T2's in 40 healthy volunteers, and OA and constant stimulus responses in 12 patients with chronic pain and 12 matched healthy controls. We measured magnitude of OA ([INCREMENT]OA) and maximum visual analogue scale (VAS) latency (time to peak VAS) during constant stimulus for each individual. Pain perception kinetics were compared with analysis of variance and sought for correlations with psychophysical parameters with a significance threshold at P < 0.05. In healthy controls, longer T2 at 10 or 15 seconds resulted in larger [INCREMENT]OA compared with T2 at 5 seconds (P = 0.04). In patients, [INCREMENT]OA was significantly smaller than controls at T2 = 5 or 10 seconds (P < 0.05) but grew comparable at T2 = 15 seconds with controls. Maximum VAS latency was longer in patients than in controls and negatively correlated with [INCREMENT]OA in patients. An OA index ([INCREMENT]OA/[maximum VAS latency]) proved diagnostic of chronic pain with an area under the receiver operating characteristic curve at 0.897. Patients with chronic pain showed impairment of OA and reduced temporal sharpening of pain perception, which might imply possible disturbance of the endogenous pain modulatory system.

TRPM2 and warmth sensation

The abilities to detect warmth and heat are critical for the survival of all animals, both in order to be able to identify suitable thermal environments for the many different activities essential for life and to avoid damage caused by extremes of temperature. Several ion channels belonging to the TRP family are activated by non-noxious warmth or by heat and are therefore plausible candidates for thermal detectors, but identifying those that actually regulate warmth and heat detection in intact animals has proven problematic. TRPM2 has recently emerged as a likely candidate for the detector of non-noxious warmth, as it is expressed in sensory neurons, and mice show deficits in the detection of warmth when TRPM2 is genetically deleted. TRPM2 is a chanzyme, containing a thermally activated TRP ion channel domain attached to a C-terminal motif, derived from a mitochondrial ADP ribose pyrophosphatase, that confers on the channel sensitivity to ADP ribose and reactive oxygen species such as hydrogen peroxide. Several open questions remain. Male mammals prefer cooler environments than female, but the molecular basis of this sex difference is unknown. TRPM2 plays a role in regulating body temperature, but are other warmth-detecting mechanisms also involved? TRPM2 is expressed in autonomic neurons, but does it confer a sensory function in addition to the well-known motor functions of autonomic neurons? TRPM2 is thought to play important roles in the immune system, in pain and in insulin secretion, but the mechanisms are unclear. TRPM2 has to date received less attention than many other members of the TRP family but is rapidly assuming importance both in normal physiology and as a key target in disease pathology.

Somatosensory changes at forearm donor sites following three different surgical flap techniques

BACKGROUND

The aim of this study was to investigate the somatosensory changes at the forearm donor region after using different types of modified flap surgical techniques.

METHODS

Thirty-one patients, who underwent oral and maxillofacial reconstructive surgery involving the use of a traditional radial forearm flap (TRFF) or two modified radial forearm flap techniques (MRFF-I; MRFF-II), participated in the study. Cold detection threshold (CDT), warm detection threshold (WDT), cold pain threshold (CPT), heat pain threshold (HPT), pressure pain threshold (PPT), mechanical detection threshold (MDT), and mechanical pain threshold (MPT) were assessed at four sites of the forearms corresponding to the middle of the vascular pedicle (VP) area, the middle of the forearm flap area, and the corresponding contralateral sites (cVP and cFF) at about 5.0 ± 1.9 months after the surgery. Data were analysed with one-way ANOVA, and post-hoc tests were performed using Tukey's Honest Significant Difference test.

RESULTS

Significant differences between the VP and cVP sites were detected for WDT (P < 0.001) in TRFF and for WDT (P < 0.001) and MDT (P = 0.006) in MRFF-I. Significant differences among TRFF, MRFF-I, and MRFF-II at the VP site were detected for CDT (P = 0.022), WDT (P < 0.001), and MDT (P = 0.015). MRFF-II was associated with significantly higher sensitivity compared to that of TRFF for WDT (P = 0.017) and higher sensitivity compared to that of MRFF-I for CDT (P = 0.017), WDT (P < 0.001), and MDT (P = 0.013).

CONCLUSIONS

Significant sensory loss was detected for all types of surgical procedures with free forearm flaps. However, the MRFF-II was associated with a better sensory recovery at short follow-up after surgery. These results suggest that a longer follow-up period and larger sample size should be included in future studies.

Quantitative sensory testing (QST) in the orofacial region of healthy Chinese: influence of site, gender and age

OBJECTIVE

To establish a preliminary thermal and mechanical somatosensory profile using a standardized quantitative sensory testing (QST) to investigate site, gender and age differences in healthy Chinese.

MATERIALS AND METHODS

Twenty younger (age: 20-40 years, 10 men, 10 women) and twenty older (age: 41-61 years, 10 men, 10 women) healthy participants completed the study. Cold detection threshold (CDT), warm detection threshold (WDT), cold pain threshold (CPT), heat pain threshold (HPT), mechanical detection threshold (MDT) and mechanical pain threshold (MPT) were measured at five sites: Left hand, bilaterally at the mental area, tip of tongue and the lower lip mucosa. Mixed model ANOVAs with repeated measures were used to analyze the data.

RESULTS

MDT(p < .001) and MPT (p < .05) were significantly higher on the hand compared to the mental areas. The CDT ( p = .006) was significantly higher and WDT (p < .001) was significantly lower at the tongue compared to lip mucosa and CDT (p < .001) was higher at the tongue mucosa than at the mental areas. WDT (p < .001) and HPT (p < .05) were significantly higher at the tip of the tongue and the lower lip mucosa compared to the mental areas. Significantly lower sensitivity for WDT (p < .001) and CDT (p = .004) were found in the older group compared to the younger group. Significant gender differences were found with less sensitivity for WDT (p = .024) and MDT (p = .003) in men compared to women.

CONCLUSIONS

Application of standardized QST can provide valuable information of orofacial somatosensory phenotypes in a Chinese population. Age, gender and site are mandatory to control for.

Different pain responses to chronic and acute pain in various ethnic/racial groups

AIM

Our goal in this study was to review the similarities and differences among ethnic groups and their respective responses to acute and chronic clinically related and experimentally induced pain.

METHOD

In this review, the PUBMED and Google-Scholar databases were searched to analyze articles that have assessed the variations in both acute and chronic pain responses among different ethnic/racial groups.

RESULTS

According to the results from 42 reviewed articles, significant differences exist among ethnic-racial groups for pain prevalence as well as responses to acute and chronic pain. Compared with Caucasians, other ethnic groups are more susceptible to acute pain responses to nociceptive stimulation and to the development of long-term chronic pain.

CONCLUSION

These differences need to be addressed and assessed more extensively in the future in order to minimize the pain management disparities among various ethnic-racial groups and also to improve the relationship between pain management providers and their patients.

Validation of the Mandarin Chinese Version of the Pain Sensitivity Questionnaire

BACKGROUND AND AIM

The Pain Sensitivity Questionnaire (PSQ), a self-reported scale, has been used to assess the pain sensitivity level in a Caucasian population. However, a validated Mandarin Chinese version of the PSQ is not available. This study was aimed to translate the PSQ into Mandarin Chinese (PSQ-C) and validate it to measure pain sensitivity among Chinese people.

METHODS

The English version of the PSQ has been translated into Mandarin Chinese (PSQ-C), according to the standard steps of cross-cultural adaptation of self-reported scales. Three of the 17 items were revised owing to cultural adaptation. The final version was validated on a population of 182 Chinese people in Changsha City, China, during October to December 2015. The participants underwent electrical experimental pain testing. The psychometric properties of the PSQ-C and its subscales were examined.

RESULTS

The Cronbach's alpha coefficients for the PSQ-C-total, PSQ-C-moderate, and PSQ-C-minor were 0.90, 0.86, and 0.81, respectively. Acceptable test-retest reliability, content validity, and construct validity were demonstrated. Concurrent validity was shown via significant positive correlations between PSQ-C scores and perceived pain intensity at pain threshold and during pain stimulation with a fixed intensity. Convergent validity was shown via significant positive correlations between Pain Catastrophizing Scale scores and PSQ-C scores. Known group validity was demonstrated via higher PSQ-C-total and PSQ-C-moderate scores among those with high neuroticism scores. These results indicate that the PSQ-C has reasonably good psychometric properties, similar to the original English and German versions.

CONCLUSION

The PSQ-C is a reliable and useful tool to assess pain sensitivity levels in a Chinese population.

Normative values of quantitative sensory testing in Hispanic Latino population

BACKGROUND

Quantitative Sensory Testing (QST) is more often used because of the increasing recognition of small fiber neuropathy.

METHODS

We studied QST in a systematic way in an age-stratified cohort of 83 neurological-free Hispanic Latinamerican patients. Predefined standardized stimuli were applied using the method of limits.

RESULTS

WDT range from 2.2 to 3.3°C in hands, and from 4.0°C up to 6.6°C in feet. Cold detection threshold range from 2.2 to 3.6°C in hands, and from 2.6°C to 4.5°C in feet. Heat-induced pain (HP) was induced at lower temperatures than previously reported, with a range from 41.8°C to 44.5°C in hands and from 43.2 to 45.7°C in feet. Similar to HP, cold pain was also induced at much higher temperatures, between 21.4-17.3°C in hands and 21.5-16.5°C in feet. Vibratory stimuli ranged from 0.8 to 1.7 μ/sec in hands and from 1.4 to 3.5 μ/sec in feet.

CONCLUSION

Temperature and vibration thresholds were similar to those previously reported in other populations except for pain thresholds that were lower in this population than in the Caucasian population.

Short-term effects of orthognathic surgery on somatosensory function and recovery pattern in the early postoperative period

We examined the short-term surgical effects of orthognathic surgery on somatosensory function. Observations were made over a short period: 3 months postoperatively. In total, 14 patients and 32 healthy controls participated. Among the 14 patients, one underwent bilateral sagittal split osteotomy alone and 13 underwent bilateral sagittal split osteotomy in combination with a Le Fort I osteotomy. A modified quantitative sensory testing (QST) protocol (the German Research Network on Neuropathic Pain, DFNS) was used to evaluate clinically the skin of the chin for sensory disturbances before surgery and at 1 week, 1 month, and 3 months postoperatively. A visual analog scale and the Japanese Version of the McGill Pain Questionnaire were completed by all participants. Both sides of the mandible showed postoperative functional loss in cold detection threshold, warmth detection threshold, thermal sensory limen, and mechanical detection threshold. All function gradually recovered to baseline conditions at 3 months postoperatively. Cold detection threshold, warmth detection threshold, thermal sensory limen, and mechanical detection threshold appeared to be useful QST parameters for evaluating neurosensory disturbances during the early postoperative period. (J Oral Sci 58, 177-184, 2016).

Somatosensory abnormalities in Chinese patients with painful temporomandibular disorders

Background

The somatosensory phenotype of Chinese temporomandibular disorders (TMD) patients is not sufficiently studied with the use of contemporary techniques and guidelines.

Methods

A standardized quantitative sensory testing (QST) battery consisting of 13 parameters with a stringent statistical protocol developed by the German Research Network on Neuropathic Pain was performed over the most painful and corresponding contralateral sites as well as the right hand of 40 Chinese patients with TMD and pain classified according to the Diagnostic Criteria for TMD (DC/TMD). The same QST protocol was performed bilaterally over the infraorbital, mental, and hand regions of 70 age- and gender-stratified healthy Chinese controls. Z-scores and loss/gain scores were computed for each TMD patient.

Results

For patients, 82.5 % had somatosensory abnormalities in the painful facial region, while 60.0 % had abnormalities confined to the right hand. The most frequent abnormalities were somatosensory gain to pinprick (35.0 %) and pressure (35.0 %) stimuli, somatosensory loss to pinprick (25.0 %), cold (22.5 %), and heat (15.0 %) nociceptive stimuli. The most frequent loss/gain score was L0G2 (no somatosensory loss combined with a gain of mechanical somatosensory function) for both the facial (40.0 %) and hand (27.5 %) regions. Involving side-to-side differences in the evaluation increased the diagnostic sensitivity by 2.5–25.0 % across different parameters.

Conclusions

Somatosensory abnormalities were commonly detected in Chinese TMD pain patients both within and outside the primary painful region, strongly indicating disturbances in the central processing of somatosensory stimuli. The individual variations in somatosensory abnormalities indicate a possible need for development of individualized TMD pain management.

Electronic supplementary material

The online version of this article (doi:10.1186/s10194-016-0632-y) contains supplementary material, which is available to authorized users.

Effect of negative emotions evoked by light, noise and taste on trigeminal thermal sensitivity

Background

Patients with migraine often have impaired somatosensory function and experience headache attacks triggered by exogenous stimulus, such as light, sound or taste. This study aimed to assess the influence of three controlled conditioning stimuli (visual, auditory and gustatory stimuli and combined stimuli) on affective state and thermal sensitivity in healthy human participants.

Methods

All participants attended four experimental sessions with visual, auditory and gustatory conditioning stimuli and combination of all stimuli, in a randomized sequence. In each session, the somatosensory sensitivity was tested in the perioral region with use of thermal stimuli with and without the conditioning stimuli. Positive and Negative Affect States (PANAS) were assessed before and after the tests. Subject based ratings of the conditioning and test stimuli in addition to skin temperature and heart rate as indicators of arousal responses were collected in real time during the tests.

Results

The three conditioning stimuli all induced significant increases in negative PANAS scores (paired t-test, P ≤0.016). Compared with baseline, the increases were in a near dose-dependent manner during visual and auditory conditioning stimulation. No significant effects of any single conditioning stimuli were observed on trigeminal thermal sensitivity (P ≥0.051) or arousal parameters (P ≥0.057). The effects of combined conditioning stimuli on subjective ratings (P ≤0.038) and negative affect (P = 0.011) were stronger than those of single stimuli.

Conclusions

All three conditioning stimuli provided a simple way to evoke a negative affective state without physical arousal or influence on trigeminal thermal sensitivity. Multisensory conditioning had stronger effects but also failed to modulate thermal sensitivity, suggesting that so-called exogenous trigger stimuli e.g. bright light, noise, unpleasant taste in patients with migraine may require a predisposed or sensitized nervous system.

Reliability study of thermal quantitative sensory testing in healthy Chinese

BACKGROUND

Test-retest reliability is important to establish for any diagnostic tool. The reliability of quantitative sensory testing (QST) in the trigeminal region has recently been described in Caucasians as well as differences in absolute thresholds and responses between Caucasians and Chinese. However, the test-retest reliability has not been determined in a Chinese population.

OBJECTIVE

To provide novel information on the test-retest reliability of thermal QST in the trigeminal and spinal system in healthy Chinese.

METHODS

Twenty healthy volunteers (10 women and 10 men) participated. Cold detection threshold (CDT), warm detection threshold (WDT), cold pain threshold (CPT), and heat pain threshold (HPT) were measured at two sites: the surface of the left hand and the left masseter. The testing was performed over three consecutive stimuli trials, three sessions conducted on one day and repeated one week later. Data were analyzed with intra-tester reliability test and four-way analysis of variance (ANOVA) for repeated measures.

RESULTS

There was a tendency for the first trial in CDT (p = 0.005), CPT (p = 0.02), and HPT (p < 0.001) to reflect higher sensitivity than the subsequent two trials. Most variables showed acceptable to excellent reliability and non-significant difference across different trials (ICC: 0.912-0.989), sessions (ICC: 0.791-0.977), and days (ICC: 0.415-0.837). Between-site differences were significant for CDT (p = 0.003) and HPT (p = 0.045) with higher sensitivity at the masseter muscle. There were significant gender differences with higher sensitivity in women for CPT (p = 0.001) and HPT (p = 0.001).

CONCLUSION

Test site and gender affect thermal thresholds substantially. The test-retest reliability of most thermal threshold measures were acceptable for assessing somatosensory function, however, innocuous thresholds appear to be associated with larger variability than noxious thresholds in a Chinese population.