Pressure pain sensitivity topographical maps reveal bilateral hyperalgesia of the hands in patients with unilateral carpal tunnel syndrome

Physical activity is predictive of conditioned pain modulation in healthy individuals: a cross-sectional study

Even in healthy populations, conditioned pain modulation (CPM) magnitude varies. This may be accounted for by (non-)modifiable factors, including physical activity. Yet, little research has thoroughly examined physical activity and its relation with CPM magnitude in a representative sample. Therefore, the present study investigated the predictive effect of physical activity on CPM magnitude in 105 healthy adults. Physical activity was assessed during seven consecutive days by self-report using the International Physical Activity Questionnaire and by monitored-based accelerometry. CPM was examined using a heterotopic noxious conditioning stimulation protocol during which the effect of a hot water conditioning stimulus on pressure pain thresholds was evaluated. Comparative, correlation, and hierarchical linear regression analyses were performed. Report-based walking predicts 4.8% of variance in pain modulatory capacity, moderate physical activity predicts 10.2% of variance in pain modulatory capacity, and report-based time spent on total physical activity predicts 7.0% of variance in pain modulatory capacity. More MET-minutes/week spent on total physical activity, including walking and moderate physical activity is associated with greater pain modulatory capacity. The findings of this study add to the limited evidence on the predictive effect of physical activity on CPM. It urges to consider physical activity a confounding factor when examining CPM. The current study provides evidence that a physically active lifestyle benefits endogenous pain modulation in healthy adults. Given its potential, walking and moderate-intensity physical activity might be achievable treatment strategies for pain patients known to have impaired CPM. PERSPECTIVE: The results of this article show that a physically active lifestyle including larger amounts of walking and moderate activity predict greater pain modulatory capacity. TRIAL REGISTRATION: This study has not been preregistered.

Comparison of early clinical outcome in carpal tunnel release - mini-open technique with palmar incision vs. endoscopic technique with wrist crease incision

BACKGROUND

The purpose of this study was to examine two techniques for Carpal Tunnel Syndrome, mini-Open Carpal Tunnel Release (mini-OCTR) and Endoscopic Carpal Tunnel Release (ECTR), to compare their therapeutic efficacy.

METHODS

Sixteen patients who underwent mini-OCTR in palmar incision and 17 patients who underwent ECTR in the wrist crease incision were included in the study. All patients presented preoperatively and at 1, 3, and 6 months postoperatively and were assessed with the Visual Analogue Scale (VAS) and the Disabilities of Arm, Shoulder and Hand Score (DASH). We also assessed the pain and cosmetic VAS of the entire affected hand or surgical wound, and the patient's satisfaction with the surgery.

RESULTS

In the objective evaluation, both surgical techniques showed improvement at 6 months postoperatively. The DASH score was significantly lower in the ECTR group (average = 3 months: 13.6, 6 months: 11.9) than in the mini-OCTR group (average = 3 months: 27.3, 6 months: 20.6) at 3 and 6 months postoperatively. Also, the pain VAS score was significantly lower in the ECTR group (average = 17.1) than in the mini-OCTR group (average = 36.6) at 3 months postoperatively. The cosmetic VAS was significantly lower in the ECTR group (average = 1 month: 15.3, 3 months: 12.2, 6 months: 5.41) than in the mini-OCTR group (average = 1 month: 33.3, 3 months: 31.2, 6 months: 24.8) at all time points postoperatively. Patient satisfaction scores tended to be higher in the ECTR group (average = 3.3) compared to the mini-OCTR group (average = 2.7).

CONCLUSIONS

ECTR in wrist increase incision resulted in better pain and cosmetic recovery in an early postoperative phase compared with mini-OCTR in palmar incision. Our findings suggest that ECTR is an effective technique for patient satisfaction.

A systematic review of the psychometric properties of pressure pain detection threshold in evaluating mechanical pain threshold in people with hand or wrist injuries

PURPOSE

The aim of this study was to conduct a systematic review of the psychometric properties of Pressure Pain Detection Threshold (PPDT) measures in people with hand or wrist injuries.

STUDY DESIGN AND METHODS

MEDLINE, Embase, and CINAHL databases were searched to identify eligible studies evaluating psychometric properties of PPDT in samples composed of at least 50% of people with hand or wrist injury. The Consensus-based Standards for the Measurement of Health Instruments' risk of bias checklist was used to critically appraise the included studies, and qualitative synthesis was performed by pooling the results of all studies that presented the same measurement property using Grading of Recommendations, Assessment, Development, and Evaluation.

RESULTS

From 415 studies, 11 relevant studies were identified. Of the 11 studies, four hand or wrist injuries were represented; carpal tunnel syndrome, distal radius fractures, osteoarthritis, and complex regional pain syndrome. Intra-rater reliability was considered sufficient (intraclass correlation coefficient 0.64-0.94), with small reported standard error of the mean values (5.3-39.2 kPa). Results of validity and responsiveness could not be synthesized due to heterogeneity. Risk of bias for reliability and measurement error was assessed as very good or adequate, whereas validity and responsiveness were doubtful or inadequate. Overall quality of evidence was low or very low for all measurement properties.

CONCLUSIONS

Inconsistent results and low quality evidence provide little confidence in the overall measurement properties of PPDT in a hand or wrist injury population. No criterion standard for pain further highlights complexities around pain measurement such that the results obtained from PPDT measures in clinical practice cannot be compared to a gold standard measure.

Effects of High-Definition Transcranial Direct Current Stimulation Targeting the Anterior Cingulate Cortex on the Pain Thresholds: A Randomized Controlled Trial

BACKGROUND

The majority of existing clinical studies used active transcranial direct current stimulation (tDCS) over superficial areas of the pain neuromatrix to regulate pain, with conflicting results. Few studies have investigated the effect of tDCS on pain thresholds by focusing on targets in deep parts of the pain neuromatrix.

METHODS

This study applied a single session of high-definition tDCS (HD-tDCS) targeting the anterior cingulate cortex (ACC) and used a parallel and sham-controlled design to compare the antinociceptive effects in healthy individuals by assessing changes in pain thresholds. Sixty-six female individuals (mean age, 20.5 ± 2.4 years) were randomly allocated into the anodal, cathodal, or sham HD-tDCS groups. The primary outcome of the study was pain thresholds (pressure pain threshold, heat pain threshold, and cold pain threshold), which were evaluated before and after stimulation through the use of quantitative sensory tests.

RESULTS

Only cathodal HD-tDCS targeting the ACC significantly increased heat pain threshold (P < 0.05) and pressure pain threshold (P < 0.01) in healthy individuals compared with sham stimulation. Neither anodal nor cathodal HD-tDCS showed significant analgesic effects on cold pain threshold. Furthermore, no statistically significant difference was found in pain thresholds between anodal and sham HD-tDCS (P > 0.38). Independent of HD-tDCS protocols, the positive and negative affective schedule scores were decreased immediately after stimulation compared with baseline.

CONCLUSIONS

The present study has found that cathodal HD-tDCS targeting the ACC provided a strong antinociceptive effect (increase in pain threshold), demonstrating a positive biological effect of HD-tDCS.

Chronic pain and local pain in usually painless conditions including neuroma may be due to compressive proximal neural lesion

It has been unexplained why chronic pain does not invariably accompany chronic pain-prone disorders. This question-driven, hypothesis-based article suggests that the reason may be varying occurrence of concomitant peripheral compressive proximal neural lesion (cPNL), e.g., radiculopathy and entrapment plexopathies. Transition of acute to chronic pain may involve development or aggravation of cPNL. Nociceptive hypersensitivity induced and/or maintained by cPNL may be responsible for all types of general chronic pain as well as for pain in isolated tissue conditions that are usually painless, e.g., neuroma, scar, and Dupuytren's fibromatosis. Compressive PNL induces focal neuroinflammation, which can maintain dorsal root ganglion neuron (DRGn) hyperexcitability (i.e., peripheral sensitization) and thus fuel central sensitization (i.e., hyperexcitability of central nociceptive pathways) and a vicious cycle of chronic pain. DRGn hyperexcitability and cPNL may reciprocally maintain each other, because cPNL can result from reflexive myospasm-induced myofascial tension, muscle weakness, and consequent muscle imbalance- and/or pain-provoked compensatory overuse. Because of pain and motor fiber damage, cPNL can worsen the causative musculoskeletal dysfunction, which further accounts for the reciprocity between the latter two factors. Sensitization increases nerve vulnerability and thus catalyzes this cycle. Because of these mechanisms and relatively greater number of neurons involved, cPNL is more likely to maintain DRGn hyperexcitability in comparison to distal neural and non-neural lesions. Compressive PNL is associated with restricted neural mobility. Intermittent (dynamic) nature of cPNL may be essential in chronic pain, because healed (i.e., fibrotic) lesions are physiologically silent and, consequently, cannot provide nociceptive input. Not all patients may be equally susceptible to develop cPNL, because occurrence of cPNL may vary as vary patients' predisposition to musculoskeletal impairment. Sensitization is accompanied by pressure pain threshold decrease and consequent mechanical allodynia and hyperalgesia, which can cause unusual local pain via natural pressure exerted by space occupying lesions or by their examination. Worsening of local pain is similarly explainable. Neuroma pain may be due to cPNL-induced axonal mechanical sensitivity and hypersensitivity of the nociceptive nervi nervorum of the nerve trunk and its stump. Intermittence and symptomatic complexity of cPNL may be the cause of frequent misdiagnosis of chronic pain.

Pressure pain threshold map of thoracolumbar paraspinal muscles after lengthening contractions in young male asymptomatic volunteers

This study aimed to characterise topographic distribution of pressure pain thresholds (PPTs) of thoracolumbar paraspinal muscles and its change after lengthening contractions (LCs) of the back muscles. Using young male asymptomatic participants in Experiment 1, we systematically examined the distribution of PPTs bilaterally in the range of Th1–L5 at measurement points 2 and 4 cm from the midline. PPTs were found to be higher in the lumbar segments of the paraspinal muscles than in the thoracic segments, and in muscles closer to the vertebrae (2 vs. 4 cm from the midline). The PPTs did not differ between the left and right sides in each segment. In Experiment 2, LC was applied by asking a part of participants recruited in Experiment 1 to fall their trunk from a starting position (parallel to the floor) to 40° flexed position, and then made it back as quickly as possible to the starting position. This cycle was repeated until participants could not keep contractions (30 times/set, 25.4 ± 10.6 sets). PPTs of the LC group decreased prominently in the lower thoracic and lumbar segments, and the decrease was more evident 24 h after LC compared to that 48 h after. In contrast, PPTs in the control group without LC remained unchanged. These results provided broad topographic images of PPTs in the thoracolumbar paraspinal muscles of young male participants with and without LC, and the obtained PPT maps could be a useful guide for better treatment of exercise-induced myofascial pain in the lower back.

Pain mechanisms in carpal tunnel syndrome: a systematic review and meta-analysis of quantitative sensory testing outcomes

ABSTRACT

Carpal tunnel syndrome (CTS) is the most common nerve compression in the arm. A mix of peripheral and central contributions on quantitative sensory testing (QST) has been reported in the literature. Thus, this systematic review or meta-analysis aimed to identify the dominant sensory phenotype and draw conclusive evidence about the presence of central sensitization (CS) in CTS. Based on an a priori published protocol and using PRISMA guidelines, 7 databases were searched (Embase, Web of Science, Scopus, PubMed, SAGE, EBSCOhost, and ProQuest). Eligible studies compared the QST findings of individuals with subacute and chronic CTS with those of healthy controls through thermal, mechanical, and vibration detection thresholds; thermal, pressure, and mechanical pain thresholds; mechanical pain sensitivity; presence of allodynia; wind-up ratio; and conditioned pain modulation. Thirty-seven studies were included in the qualitative analysis. Results showed a significant loss of all detection thresholds of hand median nerve territories and hand extramedian areas (little finger and hand dorsum) in CTS (P < 0.05) but no significant difference (P > 0.05) in wind-up ratio, cold, heat, or mechanical pain thresholds of the median nerve territories. Furthermore, there was a significant increase in mechanical pain sensitivity in median nerve territories and remotely in the forearm (P < 0.05) and a significant gain in pressure and heat pain thresholds in the carpal area (P < 0.05). Conditioned pain modulation was impaired in CTS. Hypoesthesia and increased thermal and mechanical pain ratings are the dominant sensory phenotype with inconclusive evidence about CS in CTS due to the heterogenous results of thermal and mechanical pain thresholds.

Signs of Central Hypersensitivity, Stress, and Anxiety following Treatment for Breast Cancer: A Case Control Study

Background

With treatment for breast cancer, women treated may present significant sensory abnormalities in the upper extremity. However, there are no conclusive studies that have evaluated pressure pain thresholds (PPT) in the shoulder of postoperated women for breast cancer. The aim of this study was to compare PPT in the shoulder, stress, anxiety, depression symptoms, and quality of sleep among postoperated women for breast cancer (PO group) and asymptomatic women of shoulder pain (control group).

Methods

40 women participated (n = 20, PO group, age: average ± standard deviation, 49.2 ± 8.3 years; body mass index (BMI): 27.5 ± 3.0 kg/cm²; surgery time: 22.2 ± 34.4 months; n = 20, control group, 46.9 ± 8.1 years; BMI: 26.8 ± 3.5 kg/cm²). The PPT was evaluated with a digital algometer at 32 points in the shoulder region and one control point in the tibialis anterior. Stress, anxiety, and depression were evaluated with the Depression, Anxiety and Stress Scale 21 (DASS-21) and the quality of sleep by the Pittsburgh Sleep Quality Index.

Results

Significant differences were observed over 1.5 kgf/cm² in 33 points evaluated (p < 0.01) with a small to high effect size (Cliff's delta range = 0.16; 0.92) and higher levels of anxiety and stress in the PO group (anxiety: median [first; third quartile], 5[3; 12.5]; stress: 9.7 ± 4.7 (7.8; 11.8)) in comparison with the control group (anxiety: 2.5[1; 4.8]; stress: 6.7 ± 3.31 (5.2; 8.3), (p < 0.05)). No significant differences were found between the groups in depression and sleep quality (p > 0.05).

Conclusion

Postoperated women for breast cancer present hyperalgesia in the shoulder anterior and posterior region, low PPT in the tibialis anterior, and higher levels of stress and anxiety compared to the control group.

Understanding central sensitization for advances in management of carpal tunnel syndrome

Carpal tunnel syndrome is the most common nerve compression disorder of the upper extremity, and it is traditionally considered a peripheral neuropathy associated with a localized compression of the median nerve just at the level of the carpal tunnel. Surgery and physiotherapy are treatment approaches commonly used for this condition; however, conflicting clinical outcomes suggest that carpal tunnel syndrome may be more complex. There is evidence supporting the role of peripheral nociception from the median nerve in carpal tunnel syndrome; however, emerging evidence also suggests a potential role of central sensitization. The presence of spreading pain symptoms (e.g. proximal pain), widespread sensory changes, or bilateral motor control impairments in people presenting with strictly unilateral sensory symptoms supports the presence of spinal cord changes. Interestingly, bilateral sensory and motor changes are not directly associated with electrodiagnostic findings. Other studies have also reported that patients presenting with carpal tunnel syndrome exhibit neuroplastic brainstem change supporting central sensitization. Current data would support the presence of a central sensitization process, mediated by the peripheral drive originating in the compression of the median nerve, in people with carpal tunnel syndrome. The presence of altered nociceptive gain processing should be considered in the treatment of carpal tunnel syndrome by integrating therapeutic approaches aiming to modulate long-lasting nociceptive barrage into the central nervous system (peripheral drive) and strategies aiming to activate endogenous pain networks (central drive).

Psychosocial Risk Factors and the Association With Carpal Tunnel Syndrome: A Systematic Review

BACKGROUND

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy of the upper limb. Research has shown that associative factors for CTS include occupational and biomechanical elements, sex, and age. To date, no systematic review has been undertaken to determine specifically whether there are any psychosocial risk factors in developing CTS. The objective is to determine whether psychosocial factors are associated with and/or predict the development of CTS.

METHODS

A systematic review was conducted including searches of PubMed (MEDLINE), EMBASE, and CINAHL from inception to May 30, 2017. Quantitative studies must have investigated a minimum of 1 or more psychosocial factors-cognitive, affective, behavioral, vocational, or interpersonal processes (eg, social support)-and include a point or risk estimate. One reviewer conducted the search and 2 reviewers independently assessed eligibility and completed methodological quality assessment using a modified Downs and Black checklist. Data were analyzed narratively.

RESULTS

Six moderate- to high-quality studies were included in the final review. Five studies reported a positive association between psychosocial factors and CTS, where psychosocial factors were more in those who reported CTS. One study reported no positive or negative association with CTS development. Four studies reported a negative association between psychosocial factors and CTS, where psychosocial factors were less in those who reported CTS.

CONCLUSIONS

There is limited evidence for a positive association between psychosocial factors and CTS. However, this was not a consistent finding across all included studies. Further research is indicated in standardizing CTS diagnostic criteria and investigating other working environments.

Influence of centrally mediated symptoms on functional outcomes after carpal tunnel release

Patients with carpal tunnel syndrome (CTS) often show bilaterally increased pain sensitivity and widespread symptoms. We evaluated the influence of centrally mediated symptoms on functional outcomes of carpal tunnel release (CTR). A total of 120 patients with surgically treated CTS were enrolled. Centrally mediated symptoms were preoperatively measured by administering a self-reported central sensitization inventory (CSI) questionnaire and peripheral sensitization was measured by assessing patient's pressure pain thresholds (PPT) in the forearm. Boston Carpal Tunnel Questionnaires (BCTQ) were assessed preoperatively and postoperatively at 3 and 12 months. CSI scores slightly correlated with symptom duration and moderately correlated with preoperative BCTQ scores, while PPT slightly correlated with the BCTQ scores. At 3 months, BCTQ symptom and function scores moderately correlated with lower PPTs and higher CSI scores. At 12 months, only severe electrophysiological grade was associated with BCTQ function scores. Multivariable analysis revealed that preoperative PPT, CSI, and female gender were associated with BCTQ scores at 3 months; these factors failed to be associated for 12-month outcomes. Centrally mediated symptoms measured by CSI and peripheral sensitization measured by PPTs correlated with symptom severity and duration. They were associated with poorer functional outcomes after CTR up to 3 months. However, they did not show persistent effects in the long term.

Carpal tunnel syndrome: just a peripheral neuropathy?

Carpal tunnel syndrome (CTS) is considered just a peripheral neuropathy of the upper extremity associated to the compression of the median nerve. There is evidence suggesting the presence of complex sensitization mechanisms in CTS. These processes are manifested by symptoms in extra-median regions and the presence of bilateral sensory and motor impairments. These sensory and motor changes are not associated to electrodiagnostic findings. The presence of sensitization mechanisms suggests that CTS should not be considered just as a peripheral neuropathy. The presence of altered nociceptive gain processing should be considered for therapeutic management of CTS by considering the application of therapeutic interventions that modulate nociceptive barrage into the CNS.

Preoperative Pain Sensitization Is Associated With Postoperative Pillar Pain After Open Carpal Tunnel Release

BACKGROUND

Postoperative pillar pain (deep-seated wrist pain worsened by leaning on the heel of the hand) sometimes occurs after carpal tunnel release (CTR), leading to weakness in the hand and delayed return to work. Increased pain sensitivity has been found to be associated with worse symptoms and poorer treatment response in a number of chronic musculoskeletal conditions, but few studies have investigated the association of pain sensitization with pillar pain after CTR.

QUESTIONS/PURPOSES

(1) Is preoperative pain sensitization in patients with carpal tunnel syndrome (CTS) associated with increased severity of pillar pain after open CTR? (2) What other demographic, electrophysiological, or preoperative clinical characteristics are associated with pillar pain after CTR?

METHODS

Over a 35-month period, one surgeon performed 162 open carpal tunnel releases. Patients were eligible if they had sufficient cognitive and language function to provide informed consent and completed a self-reported questionnaire; they were not eligible if they had nerve entrapment other than CTR or if the surgery was covered by workers compensation insurance. Based on these criteria, 148 (91%) were approached for this study. Of those, 17 (9%) were lost to followup before 12 months, leaving 131 for analysis. Their mean age was 54 years (range, 32-78 years), and 81% (106 of 131) were women; 34% (45 of 131) had less than a high school education. We preoperatively measured pain sensitization by assessing the patients' pressure pain thresholds by stimulating pressure-induced pain in the pain-free volar forearm and administering a self-reported Pain Sensitivity Questionnaire minor subscale, an instrument that assesses pain intensity in daily life situations. We evaluated postoperative pillar pain using the "table test" (having the patient lean on a table with their weight on their hands placed on the table's edge with elbows straight) with an 11-point ordinal scale at 3, 6, and 12 months after their surgical procedures. We conducted bivariate and multivariable analyses to determine whether the patients' clinical, demographic, and pain sensitization factors were associated with their postoperative pillar pain severity after CTR.

RESULTS

After controlling for relevant confounding variables such as age, education level, and functional states, we found that increased pillar pain severity was associated with the pressure pain threshold (β = -1.02 [-1.43 to -0.61], partial R = 11%, p = 0.021) and Pain Sensitivity Questionnaire minor (β = 1.22 [0.73-1.71], partial R = 17%, p = 0.013) at 3 months, but by 6 months, only Pain Sensitivity Questionnaire minor (β = 0.92 [0.63-1.21], partial R = 13%, p = 0.018) remained an associated variable for pillar pain. Additionally, gender (women) was associated with increased pain severity at 3 (β = 0.78 [0.52-1.04], partial R = 9%, p = 0.023) and 6 months (β = 0.72 [0.41-1.01], partial R = 8%, p = 0.027). At 3 months, pressure pain threshold, Pain Sensitivity Questionnaire minor, and gender (women) collectively accounted for 37% of the variance in pillar pain severity; at 6 months, Pain Sensitivity Questionnaire minor and gender (women) accounted for 21% of the variance, but no relationship between those factors and pillar pain was observed at 12 months.

CONCLUSIONS

Gender (women) and preoperative pain sensitization measured by pressure pain threshold and self-reported Pain Sensitivity Questionnaire were associated with pillar pain severity up to 3 and 6 months after CTR, respectively. However, the influence of pain sensitization on pillar pain was diminished at 6 months and it did not show persistent effects beyond 12 months. Pain sensitization seems to be more important in the context of recovery from surgical intervention (in the presence of a pain condition) than in healthy states, and clinicians should understand the role of pain sensitization in the postoperative management of CTS. Future research may be needed to determine if therapeutic interventions to reduce sensitization will decrease the risk of pillar pain.

LEVEL OF EVIDENCE

Level III, prognostic study.

Ultrasound plus low-level laser therapy for knee osteoarthritis rehabilitation: a randomized, placebo-controlled trial

This study evaluated the synergistic effects of ultrasound (US) and low-level laser therapy (LLLT) with or without therapeutic exercises (TE) in women with knee osteoarthritis. Forty-two Caucasian women with knee osteoarthritis were allocated into three groups: (1) the placebo group who did not perform TE, but the prototype without emitting light or ultrasonic waves was applied, (2) the US + LLLT group in which only the prototype was applied and (3) the TE + US + LLLT group that performed TE before the prototype was applied. However, 35 women completed the full clinical trial. Pressure pain thresholds (PPT) using an algometer and functional performance during the sit-to-stand test were carried out. The average PPT levels increased for US + LLLT (41 ± 9 to 54 ± 15 N, p < 0.01) and TE + US + LLLT (32 ± 8 to 45 ± 9 N, p < 0.01) groups. The number of sit-to-stands was significantly higher for all groups. However, the change between pre-treatment and post-treatment (delta value) was greater for the US + LLLT (4 ± 1) and TE + US + LLLT groups (5 ± 1) than for the placebo group (2 ± 1) with a significant intergroup difference (p < 0.05). This study showed reduced pain and increased physical functionality after 3 months of US + LLLT with and without TE.

Spotlight on topographical pressure pain sensitivity maps: a review

Mechanical hyperalgesia defined as decreased pressure pain thresholds (PPTs) is commonly associated with pain. In this narrative review, we report the current state of the art within topographical pressure sensitivity maps. Such maps are based on multiple PPT assessments. The PPTs are assessed by an a priori defined grid with special focus on both spatial and temporal summation issues. The grid covers the muscle or the body region of interest using absolute or relative values determined from anatomical landmarks or anthropometric values. The collected PPTs are interpolated by Shepard or Franke and Nielson interpolation methods to create topographical pressure sensitivity maps. This new imaging technique has proven to be valuable in various disciplines including exercise physiology, neurology, physical therapy, occupational medicine, oncology, orthopedics, and sport sciences. The reviewed papers have targeted different body regions like the scalp, low back, neck-shoulder, and upper and lower extremities. The maps have delineated spatial heterogeneity in the pressure pain sensitivity underlining the different extents of pressure pain hyperalgesia in both experimentally induced and disease-associated pain conditions. Furthermore, various intervention studies have proven the utility of topographical pressure pain sensitivity maps. Topographical pressure pain sensitivity maps have contributed to revealing the efficacy of therapeutic, ergonomic, or training interventions that aim at reducing pain.

Facilitatory and inhibitory pain mechanisms are altered in patients with carpal tunnel syndrome

Preliminary evidence from studies using quantitative sensory testing suggests the presence of central mechanisms in patients with carpal tunnel syndrome (CTS) as apparent by widespread hyperalgesia. Hallmarks of central mechanisms after nerve injuries include nociceptive facilitation and reduced endogenous pain inhibition. Methods to study nociceptive facilitation in CTS so far have been limited to quantitative sensory testing and the integrity of endogenous inhibition remains unexamined. The aim of this study was therefore to investigate changes in facilitatory and inhibitory processing in patients with CTS by studying hypersensitivity following experimentally induced pain (facilitatory mechanisms) and the efficacy of conditioned pain modulation (CPM, inhibitory mechanisms). Twenty-five patients with mild to moderate CTS and 25 age and sex matched control participants without CTS were recruited. Increased pain facilitation was evaluated via injection of hypertonic saline into the upper trapezius. Altered pain inhibition through CPM was investigated through cold water immersion of the foot as the conditioning stimulus and pressure pain threshold over the thenar and hypothenar eminence bilaterally as the test stimulus. The results demonstrated that patients with CTS showed a greater duration (p = 0.047), intensity (p = 0.044) and area (p = 0.012) of pain in response to experimentally induced pain in the upper trapezius and impaired CPM compared to the control participants (p = 0.006). Although typically considered to be driven by peripheral mechanisms, these findings indicate that CTS demonstrates characteristics of altered central processing with increased pain facilitation and reduced endogenous pain inhibition.

Intra-session absolute and relative reliability of pressure pain thresholds in the low back region of vine-workers: ffect of the number of trials

BACKGROUND

Pressure pain thresholds (PPT) are commonly used to quantify mechanical pain sensitivity of deep structures. Excellent PPT reliability has been previously reported among the low back of healthy subjects. However, there is a lack of studies assessing PPT over the low back of workers exposed to biomechanical risk factors of low back pain. Thus, the purpose of this study was threefold: (1) to evaluate the intra-session absolute and relative reliability as well as minimal detectable change (MDC) values of PPT within 14 locations covering the low back region of vine-workers and (2) to determine the number of trial required to ensure reliable PPT assessments and (3) to assess the effect of modifier factors such as gender, age, body mass index (BMI) and pain intensity on PPT reliability.

METHODS

Twenty-nine vine-workers voluntarily participated in this study. Twenty-two reported low intensity of low-back pain while seven were pain-free. PPTs were assessed among 14 anatomical locations in the lower back region. Three trials were performed on each location with an interval time of at least one minute. Reliability was assessed computing intraclass correlation coefficients (ICC), standard error of measurement (SEM) for all possible combinations between trials. Bland-Altman plots were also generated to assess potential bias in the dataset. Finally, a repeated measure analysis of variance (RM-ANOVA) with the number of trials used as within subject factor was performed on (1) PPT, (2) ICC and (3) SEM values.

RESULTS

ICC ranged from 0.86 to 0.99 for all anatomical locations and for all possible combinations between trials. SEM for comparison between trial 1-2, 2-3, 1-3 and, 1-2-3 ranged from respectively, 36.7-77.5, 27.8-77.7, 50-95.2 and, 39.3-80.8 kPa. ICC and SEM remained similar to the ones obtained for the entire population when taking modifier factors in consideration. The visual analysis of Bland-Altman plots suggested small measurement errors for all anatomical locations and for all possible combinations between trials.

CONCLUSIONS

The assessment of PPTs of the lower back among vine-workers was found to have excellent relative and absolute reliability. Moreover, reliable measurements can be equally achieved when using the mean of three PPT measurement or with the first one.

Negative Neurodynamic Tests Do Not Exclude Neural Dysfunction in Patients With Entrapment Neuropathies

Objective

To examine differences in somatosensory phenotypes of patients with positive and negative neurodynamic tests and compare these with healthy participants.

Design

Case-control study.

Setting

University department.

Participants

Patients with electrodiagnostically confirmed carpal tunnel syndrome (CTS) (n=53) and people without CTS (n=26) participated in this study (N=79). Patients with CTS were subgrouped according to the results of the upper limb neurodynamic tests biasing the median nerve into patients with positive or negative neurodynamic tests.

Interventions

Not applicable.

Main Outcome Measure

All participants underwent quantitative sensory testing in the median innervated territory of their hand.

Results

Only 46% of patients with CTS had positive neurodynamic tests. No differences were identified between groups for pain thresholds (P>.247). However, patients with CTS had increased mechanical (P<.0001) and thermal detection thresholds (P<.0001) compared with people without CTS. Patients with negative neurodynamic tests had a more pronounced vibration detection deficit (mean, 7.43±0.59) than people without CTS (mean, 7.89±0.22; P=.001). Interestingly, warm detection was the only domain differentiating positive (mean, 4.03°C±2.18°C) and negative neurodynamic test groups (6.09°C±3.70°C, P=.032), with patients with negative neurodynamic tests demonstrating increased loss of function.

Conclusions

Patients with negative neurodynamic tests seem to have a more severe dysfunction of the unmyelinated fiber population. Our findings suggest that neurodynamic tests should not be used in isolation to judge neural involvement. Rather, they should be interpreted in the context of loss of function tests of the small fiber domain.

Muscle Trigger Points and Pressure Pain Sensitivity Maps of the Feet in Women with Fibromyalgia Syndrome

OBJECTIVE : To investigate the presence of trigger points (TrPs) in feet musculature and topographical pressure sensitivity maps of the feet as well as the relationship between TrPs, pressure pain maps, and clinical variables in women with fibromyalgia (FMS). METHODS : Fifty-one FMS women and 24 comparable healthy women participated. TrPs within the flexor hallucis brevis, adductor hallucis, dorsal interossei, extensor digitorum brevis, and quadratus plantae, as well as external and internal gastrocnemius, were explored. Pressure pain thresholds (PPTs) were assessed in a blind manner over seven locations on each foot. Topographical pressure sensitivity maps of the plantar region were generated using the averaged PPT of each location. RESULTS : The prevalence rate of foot pain was 63% (n = 32). The number of active TrPs for each FMS woman with foot pain was 5 ± 1.5 without any latent TrPs. Women with FMS without foot pain and healthy controls had only latent TrPs (2.2 ± 0.8 and 1.5 ± 1.3, respectively). Active TrPs in the flexor hallucis brevis and adductor hallucis muscles were the most prevalent. Topographical pressure pain sensitivity maps revealed that FMS women with foot pain had lower PPT than FMS women without pain and healthy controls, and higher PPT on the calcaneus bone (P < 0.001). CONCLUSIONS : The presence of foot pain in women with FMS is high. The referred pain elicited by active TrPs in the foot muscles reproduced the symptoms in these patients. FMS women suffering foot pain showed higher pressure hypersensitivity in the plantar region than those FMS women without pain.

A meta-analysis of site-specific effects of cathodal transcranial direct current stimulation on sensory perception and pain

The primary aim of our meta-analysis was to evaluate the effects of cathodal transcranial direct current stimulation (c-tDCS) on sensory and pain thresholds (STh and PTh) in healthy individuals and pain level (PL) in patients with chronic pain. Electronic databases were searched for c-tDCS studies. Methodological quality was evaluated using the PEDro and Downs and Black (D&B) assessment tools. C-tDCS of the primary motor cortex (S1) increases both STh (P<0.001, effect size of 26.84%) and PTh (P<0.001, effect size of 11.62%). In addition, c-tDCS over M1 led to STh increase (P<0.005, effect size of 30.44%). Likewise, PL decreased significantly in the patient group following application of c-tDCS. The small number of studies precluded subgroup analysis. Nevertheless, meta-analysis showed that in all groups (except c-tDCS of S1) active c-tDCS and sham stimulation produced significant differences in STh/PTh in healthy and PL in patient group. This review provides evidence for the site-specific effectiveness of c-tDCS in increasing STh/PTh in healthy individuals and decreasing PL in patients with chronic pain. However, due to small sample sizes in the included studies, our results should be interpreted with caution. Given that the level of blinding was not considered in the inclusion criteria, the results of the current study should be interpreted with caution.

How does anodal transcranial direct current stimulation of the pain neuromatrix affect brain excitability and pain perception? A randomised, double-blind, sham-control study

Background

Integration of information between multiple cortical regions of the pain neuromatrix is thought to underpin pain modulation. Although altered processing in the primary motor (M1) and sensory (S1) cortices is implicated in separate studies, the simultaneous changes in and the relationship between these regions are unknown yet. The primary aim was to assess the effects of anodal transcranial direct current stimulation (a-tDCS) over superficial regions of the pain neuromatrix on M1 and S1 excitability. The secondary aim was to investigate how M1 and S1 excitability changes affect sensory (STh) and pain thresholds (PTh).

Methods

Twelve healthy participants received 20 min a-tDCS under five different conditions including a-tDCS of M1, a-tDCS of S1, a-tDCS of DLPFC, sham a-tDCS, and no-tDCS. Excitability of dominant M1 and S1 were measured before, immediately, and 30 minutes after intervention respectively. Moreover, STh and PTh to peripheral electrical and mechanical stimulation were evaluated. All outcome measures were assessed at three time-points of measurement by a blind rater.

Results

A-tDCS of M1 and dorsolateral prefrontal cortex (DLPFC) significantly increased brain excitability in M1 (p < 0.05) for at least 30 min. Following application of a-tDCS over the S1, the amplitude of the N20-P25 component of SEPs increased immediately after the stimulation (p < 0.05), whilst M1 stimulation decreased it. Compared to baseline values, significant STh and PTh increase was observed after a-tDCS of all three stimulated areas. Except in M1 stimulation, there was significant PTh difference between a-tDCS and sham tDCS.

Conclusion

a-tDCS of M1 is the best spots to enhance brain excitability than a-tDCS of S1 and DLPFC. Surprisingly, a-tDCS of M1 and S1 has diverse effects on S1 and M1 excitability. A-tDCS of M1, S1, and DLPFC increased STh and PTh levels. Given the placebo effects of a-tDCS of M1 in pain perception, our results should be interpreted with caution, particularly with respect to the behavioural aspects of pain modulation.

Trial Registration

Australian New Zealand Clinical Trials, ACTRN12614000817640, http://www.anzctr.org.au/.

Contribution of transient receptor potential ankyrin 1 to chronic pain in aged mice with complete Freund's adjuvant-induced arthritis

OBJECTIVE

To investigate age-related differences in mechanical sensitivity to inflammatory pain and determine the contribution of transient receptor potential ankyrin 1 (TRPA1) to mechanical hypersensitivity during chronic inflammation in young and aged mice with complete Freund's adjuvant (CFA)-induced arthritis.

METHODS

Mechanical sensitivity in young (3-month-old) and aged (24-month-old) wild-type (TRPA1(+/+) ) mice and TRPA1-deficient (TRPA1(-/-) ) mice was measured behaviorally for 8 weeks following injection of CFA into the plantar hind paw. The severity of inflammation was evaluated by histologic analyses and hind-paw measurements. Ex vivo preparations of the skin saphenous nerve from mice were assessed for C-fiber sensitivity.

RESULTS

Among naive (uninjured) wild-type mice, aged animals were less sensitive than young animals to mechanical stimuli. Afferent recordings of C-fibers from TRPA1(-/-) mice indicated that TRPA1 contributes to the normal mechanical sensitivity in both age groups. Following injection of CFA, both young and aged TRPA1(+/+) mice exhibited mechanical hypersensitivity. In young TRPA1(-/-) mice injected with CFA, peak development of mechanical hypersensitivity was delayed until week 4, when they exhibited a sharp decrease (9-fold) in the mechanical paw withdrawal threshold, whereas aged TRPA1(-/-) mice did not exhibit mechanical hypersensitivity at any time during the 8 weeks after CFA injection. Recordings of C-fibers from the saphenous nerve supported these findings, with results indicating that both young and aged TRPA1(+/+) mice exhibited increased action potential firing at 8 weeks after CFA injection (increases of 25% and 60%, respectively). Interestingly, among TRPA1(-/-) mice injected with CFA, mechanical firing was increased markedly in the C-fibers of young mice (increase of 80%) but not in the C-fibers of aged mice.

CONCLUSION

These findings reveal marked differences in the long-term mechanical behavioral sensitivity of aged and young mice, and suggest that TRPA1 may be a key contributor to the transition from acute to chronic inflammatory pain in response to mechanical stimuli as well as to the development of nociceptor sensitization selectively in aged mice.

Synergic effects of ultrasound and laser on the pain relief in women with hand osteoarthritis

Patients with pain avoid movements, leading to a gradual impairment of their physical condition and functionality. In this context, the use of ultrasound (US) and low-level laser therapy (LLLT) show promising results for nonpharmacological and noninvasive treatment. The aim of this study was evaluated the synergistic effects of the US and the LLLT (new prototype) with or without therapeutic exercises (TE) on pain and grip strength in women with hand osteoarthritis. Forty-five women with hand osteoarthritis, aged 60 to 80 years, were randomly assigned to one of three groups, but 43 women successfully completed the full study. The three groups were as follows: (i) the placebo group which did not perform TE, but the prototype without emitting electromagnetic or mechanical waves was applied (n = 11); (ii) the US + LLLT group which carried out only the prototype (n = 13); and (iii) the TE + US + LLLT group which performed TE before the prototype is applied (n = 13). The parameters of US were frequency 1 MHz; 1.0 W/cm(2) intensity, pulsed mode 1:1 (duty cycle 50%). Regarding laser, the output power of the each laser was fixed at 100 mW leading to an energy value of 18 J per laser. Five points were irradiated per hand, during 3 min per point and 15 min per session. The prototype was applied after therapeutic exercises. The treatments are done once a week for 3 months. Grip strength and pressure pain thresholds (PPT) were measured. Grip strength did not differ significantly for any of the groups (p ≥ 0.05). The average PPT between baseline and 3 months shows significant decrease of the pain sensitivity for both the US + LLLT group (∆ = 30 ± 19 N, p˂0.001) and the TE + US + LLLT group (∆ = 32 ± 13 N, p < 0.001). However, there were no significant differences in average PPT for placebo group (∆ = -0.3 ± 9 N). There was no placebo effect. The new prototype that combines US and LLLT reduced pain in women with hand osteoarthritis.

Relationship between electrodiagnostic severity and neuropathic pain assessed by the LANSS pain scale in carpal tunnel syndrome

OBJECTIVE

The aim of the study was to investigate the relationship between the presence of neuropathic pain assessed by the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) scale and electrophysiological findings in patients with carpal tunnel syndrome (CTS).

METHODS

We studied 124 hands with idiopathic CTS with pain complaints involving hand and wrist. All hands were assessed by the LANSS with which a score of 12 or more is defined as pain dominated by neuropathic mechanisms. These hands were assigned to minimal, mild, moderate, severe, or extreme severe groups according to the results of the median nerve conduction studies.

RESULTS

A LANSS score ≥ 12, suggestive of pain dominated by neuropathic mechanisms, was defined in 59 (47.6%) CTS hands. Pain intensity was significantly higher in CTS hands with a LANSS score ≥ 12 (P < 0.001). Among electrophysiological findings, compound muscle action potential amplitude was significantly lower in hands with a LANSS score ≥ 12 compared with hands with a LANSS score < 12 (P = 0.020). Severity of CTS was not significantly different between LANSS ≥ 12 and LANSS < 12 groups. Electrophysiological severity was significantly higher in CTS hands with evoked pain (P = 0.005) and allodynia (P < 0.001) in LANSS subscore analysis.

CONCLUSION

We suggest that the presence of pain dominated by neuropathic mechanisms in CTS is not related to electrophysiological CTS severity. Neuropathic pain should be assessed carefully in patients with CTS, and an appropriate treatment plan should be chosen, taking into account the clinical and electrophysiological findings together with the true pain classification.

Anatomical association between wrist extensor musculature and topographical pain sensitivity maps of the elbow area

OBJECTIVE

High-density topographical sensitivity maps have been developed to visualize nonuniformity deep tissue pain sensitivity in, for example, lateral epicondylitis (LE). The aim of this cadaveric study was to determine the anatomical association between the topographical sensitivity maps over the elbow area and wrist extensor musculature.

METHODS

A topographical pressure sensitivity map consisting of 12 points forming a 3 × 4 matrix: 4 points in the superior part, 4 points in the middle, and 4 points in the lower part around the lateral epicondyle was marker on a 50-year embalmed cadaver. Color marker pins were inserted into each point. Pins were removed during the process of dissection, but the small holes created by their removal assured accurate relocation.

RESULTS

Progressive dissection revealed that points 1 to 4 (superior line) were placed over the musculotendinous junction and belly of the extensor carpi radialis brevis (ECRB) muscle, points 6 to 8 (middle line) were placed over the musculotendinous junction and belly of the extensor digitorum communis muscle, and points 9 to 12 (inferior line) were located over the musculotendinous junction and belly of the extensor carpi ulnaris muscle. It was also observed that the superficial branch of the radial nerve runs between the belly of the ECRB and extensor digitorum communis muscles.

CONCLUSIONS

This study confirmed that anatomical location previously assumed supporting the important wrist extensor muscles, particularly the ECRB, in patients with LE as depicted by pressure pain sensitivity maps. This study also suggests a potential role of the superficial branch of the radial nerve in LE.

The prevalence of fibromyalgia in other chronic pain conditions

Central sensitivity syndromes (CSS) include fibromyalgia syndrome (FMS), irritable bowel syndrome, temporomandibular disorder, restless legs syndrome, chronic fatigue syndrome, and other similar chronic painful conditions that are based on central sensitization (CS). CSS are mutually associated. In this paper, prevalence of FMS among other members of CSS has been described. An important recent recognition is an increased prevalence of FMS in other chronic pain conditions with structural pathology, for example, rheumatoid arthritis, systemic lupus, ankylosing spondylitis, osteoarthritis, diabetes mellitus, and inflammatory bowel disease. Diagnosis and proper management of FMS among these diseases are of crucial importance so that unwarranted use of such medications as corticosteroids can be avoided, since FMS often occurs when RA or SLE is relatively mild.

Heightened pain sensitivity in individuals with signs and symptoms of carpal tunnel syndrome and the relationship to clinical outcomes following a manual therapy intervention

Neurophysiological responses related to lessening of pain sensitivity are a suggested mechanism of manual therapy. Prior studies have observed generalized lower pain thresholds associated with carpal tunnel syndrome (CTS) in comparison to healthy controls. The present study sought to determine whether similar findings were present in suprathreshold measures and measures specific to central integration of pain (temporal summation and after sensations). Additionally, we wished to determine whether measures of pain sensitivity were related to clinical outcomes in participants with signs and symptoms of CTS receiving a manual therapy intervention. Individuals with signs and symptoms of CTS reported greater pain sensitivity to suprathreshold measures of mechanical pain, temporal summation, and after sensation in comparison to healthy controls. Immediate lessening of mechanical pain sensitivity and after sensations in response to a manual therapy intervention and 3-week attenuation of temporal summation following a 3-week course of manual therapy were associated with 3-week changes in clinical pain intensity in participants with signs and symptoms of CTS. These findings suggest heightened pain sensitivity across several parameters may be associated with CTS. Furthermore, changes in mechanical pain, after sensation, and temporal summation may be related to improvements in clinical outcomes.

Central sensitization: implications for the diagnosis and treatment of pain

Nociceptor inputs can trigger a prolonged but reversible increase in the excitability and synaptic efficacy of neurons in central nociceptive pathways, the phenomenon of central sensitization. Central sensitization manifests as pain hypersensitivity, particularly dynamic tactile allodynia, secondary punctate or pressure hyperalgesia, aftersensations, and enhanced temporal summation. It can be readily and rapidly elicited in human volunteers by diverse experimental noxious conditioning stimuli to skin, muscles or viscera, and in addition to producing pain hypersensitivity, results in secondary changes in brain activity that can be detected by electrophysiological or imaging techniques. Studies in clinical cohorts reveal changes in pain sensitivity that have been interpreted as revealing an important contribution of central sensitization to the pain phenotype in patients with fibromyalgia, osteoarthritis, musculoskeletal disorders with generalized pain hypersensitivity, headache, temporomandibular joint disorders, dental pain, neuropathic pain, visceral pain hypersensitivity disorders and post-surgical pain. The comorbidity of those pain hypersensitivity syndromes that present in the absence of inflammation or a neural lesion, their similar pattern of clinical presentation and response to centrally acting analgesics, may reflect a commonality of central sensitization to their pathophysiology. An important question that still needs to be determined is whether there are individuals with a higher inherited propensity for developing central sensitization than others, and if so, whether this conveys an increased risk in both developing conditions with pain hypersensitivity, and their chronification. Diagnostic criteria to establish the presence of central sensitization in patients will greatly assist the phenotyping of patients for choosing treatments that produce analgesia by normalizing hyperexcitable central neural activity. We have certainly come a long way since the first discovery of activity-dependent synaptic plasticity in the spinal cord and the revelation that it occurs and produces pain hypersensitivity in patients. Nevertheless, discovering the genetic and environmental contributors to and objective biomarkers of central sensitization will be highly beneficial, as will additional treatment options to prevent or reduce this prevalent and promiscuous form of pain plasticity.