Referred Pain Area Research Articles

Long-term consistency of clinical sensory testing measures for pain assessment.

Understanding the stability of quantitative sensory tests (QSTs) over time is important to aid clinicians in selecting a battery of tests for assessing and monitoring patients. This study evaluated the short- and long-term reliability of selected QSTs. Twenty healthy women participated in three experimental sessions: Baseline, 2 weeks, and 6 months. Measurements included pressure pain thresholds (PPT) in the neck, upper back, and leg; Pressure-cuff pain tolerance around the upper-arm; conditioned pain modulation during a pressure-cuff stimulus; and referred pain following a suprathreshold pressure stimulation. Intraclass correlation coefficients (ICC) and minimum detectable change (MDC) were calculated. Reliability for PPT was excellent for all sites at 2 weeks (ICC, 0.96-0.99; MDC, 22-55 kPa) and from good to excellent at 6 months (ICC, 0.88-0.95; MDC, 47-91 kPa). ICC for pressure-cuff pain tolerance indicated excellent reliability at both times (0.91-0.97). For conditioned pain modulation, reliability was moderate for all sites at 2 weeks (ICC, 0.57-0.74; MDC, 24%-35%), while it was moderate at the neck (ICC, 0.54; MDC, 27%) and poor at the upper back and leg at 6 months. ICC for referred pain areas was excellent at 2 weeks (0.90) and good at 6 months (0.86). PPT, pressure pain tolerance, and pressure-induced referred pain should be considered reliable procedures to assess the pain-sensory profile over time. In contrast, conditioned pain modulation was shown to be unstable. Future studies prospectively analyzing the pain-sensory profile will be able to better calculate appropriate sample sizes.

Myofascial Pain Syndrome in Women with Primary Dysmenorrhea: A Case-Control Study.

There is limited information on myofascial trigger points (MTrPs) and specific symptoms of chronic pelvic pain and, more specifically, dysmenorrhea. The objective of this study was to determine whether patients suffering from primary dysmenorrhea present alterations in mechanosensitivity and pain patterns, and greater presence of MTrPs in the abdominal and pelvic floor muscles. A case-control study was carried out with a total sample of 84 participants distributed based on primary dysmenorrhea and contraceptive treatment. The sample was divided into four groups each comprising 21 women. Data on pain, quality of life, and productivity and work absenteeism were collected; three assessments were made in different phases of the menstrual cycle, to report data on pressure pain threshold, MTrP presence, and referred pain areas. One-way ANOVA tests showed statistically significant differences (p < 0.01) between the groups, for the Physical Health domain and the total score of the SF-12 questionnaire, and for all the domains of the McGill questionnaire; but no significant differences were found in the data from the WPAI-GH questionnaire. Statistically significant data (p < 0.01) were found for mechanosensitivity in the abdominal area and limbs, but not for the lumbar assessment, within the group, with very few significant intergroup differences. The frequency of active MTrPs is higher in the groups of women with primary dysmenorrhea and during the menstrual phase, with the prevalence of myofascial trigger points of the iliococcygeus muscle being especially high in all examination groups (>50%) and higher than 70% in women with primary dysmenorrhea, in the menstrual phase, and the internal obturator muscle (100%) in the menstrual phase. Referred pain areas of the pelvic floor muscles increase in women with primary dysmenorrhea.

Referred Somatic Hyperalgesia Mediates Cardiac Regulation by the Activation of Sympathetic Nerves in a Rat Model of Myocardial Ischemia.

Myocardial ischemia (MI) causes somatic referred pain and sympathetic hyperactivity, and the role of sensory inputs from referred areas in cardiac function and sympathetic hyperactivity remain unclear. Here, in a rat model, we showed that MI not only led to referred mechanical hypersensitivity on the forelimbs and upper back, but also elicited sympathetic sprouting in the skin of the referred area and C8-T6 dorsal root ganglia, and increased cardiac sympathetic tone, indicating sympathetic-sensory coupling. Moreover, intensifying referred hyperalgesic inputs with noxious mechanical, thermal, and electro-stimulation (ES) of the forearm augmented sympathetic hyperactivity and regulated cardiac function, whereas deafferentation of the left brachial plexus diminished sympathoexcitation. Intradermal injection of the α2 adrenoceptor (α2AR) antagonist yohimbine and agonist dexmedetomidine in the forearm attenuated the cardiac adjustment by ES. Overall, these findings suggest that sensory inputs from the referred pain area contribute to cardiac functional adjustment via peripheral α2AR-mediated sympathetic-sensory coupling.

Effectiveness of Transcranial Direct Current Stimulation Combined With Exercising in People With Fibromyalgia: A Randomized Sham-Controlled Clinical Trial

ObjectiveTo evaluate the effectiveness of transcranial direct current stimulation (tDCS) combined with exercising in people with fibromyalgia. DesignRandomized, triple-blind, sham-controlled, clinical trial. SettingPrimary health care center. ParticipantsA total of 120 volunteer participants (N=120) between 18 and 65 years old and diagnosed with fibromyalgia. Four participants dropped out of the study for causes unrelated to the intervention. InterventionParticipants were randomized into 3 groups (active tDCS+exercising, sham tDCS+exercising, no-intervention control). The intervention was delivered in 5 sessions over 2 weeks. Main Outcome MeasuresPain intensity and referred pain area after suprathreshold pressure stimulation. ResultsPain intensity further decreased in the active tDCS group vs control (mean, −14.43; 95% confidence interval, −25.27 to −3.58) at post intervention, unlike the sham tDCS group. Both tDCS groups did not achieve greater reductions in referred pain vs control. In the active tDCS group, health status (mean, −14.80; 95% confidence interval, −23.10 to −6.50) and pain catastrophizing (mean, −6.68, 95% confidence interval, −11.62 to −1.73) improved at post intervention, and so did health status (mean, −8.81; 95% confidence interval, −17.11 to −0.51), pain catastrophizing (mean, −7.00; 95% confidence interval, −12.13 to −1.87), and depression (mean, −3.52; 95% confidence interval, −6.86 to −0.19) after 1 month. In the sham tDCS group, improvements were recorded in health status (mean, −13.21; 95% confidence interval, −21.52 to −4.91) and depression (mean, −3.35; 95% confidence interval, −6.35 to −0.35) at post intervention and in health status (mean, −8.77; 95% confidence interval, −17.06 to −0.47), pain catastrophizing (mean, −5.68; 95% confidence interval, −10.80 to −0.55), and depression (mean, −3.98; 95% confidence interval, −7.31 to −0.64) after 1 month. No intergroup differences were observed between active and sham tDCS. ConclusionsActive and sham tDCS improved health status, pain catastrophizing, and depression vs control, but pain intensity decreased only in the active tDCS group.

Patients with symptomatic permanent atrial fibrillation show quantitative signs of pain sensitisation

Abstract Background/Introduction Most patients with atrial fibrillation (AF) report symptoms, while around one-third are asymptomatic. We hypothesized that sensory processing, in particular pain, differs in patients with symptomatic and asymptomatic AF. Purpose To assess differences in pain sensitisation in patients with symptomatic and asymptomatic AF. Methods Thirty individuals with permanent AF (15 symptomatic, 15 asymptomatic) completed the AF6 and SF-36 questionnaires and underwent quantitative pain sensitisation testing using pressure algometry at the sternum (referred pain area) and the tibialis anterior muscle (generalized pain area). The primary objective was to assess differences in pressure pain thresholds (PPT), temporal summation of pain (TSP), and conditioned pain modulation (CPM) in the two groups. The secondary objective was to determine association of demographic and clinical parameters to quantitative measures of pain sensitisation. Results The symptomatic group had lower PPTs at both tibialis (p=0.004) and sternum (p=0.01), as well as impaired CPM (p=0.025) and facilitated TSP (p=0.008) at the tibialis but not sternum, compared to the asymptomatic group. The AF6 sum score was negatively correlated to PPT on both tibialis (r=−0.50, p=0.005) and sternum (r=−0.42, p=0.02) and positively correlated to TSP of both tibialis (r=0.57, p=0.001) and sternum (r=0.45, p=0.01), but not to CPM. The physical component summary score was positively correlated to the PPT on both tibialis (r=0.52, p=0.003) and sternum (r=0.40, p=0.03) and negatively to TSP on the tibialis (r=−0.53, p=0.003) but not sternum. Conclusions Patients with symptomatic AF exhibit lower pain tolerance than patients with asymptomatic AF, as well as impaired pain inhibitory control and facilitated summation of pain, indicating that pain sensitisation may be of importance in symptomatic AF. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Department of Cardiology, Örebro University, Sweden PPTs tibialis anterior musclePPTs sternum

Changes in Pain Sensitivity and Conditioned Pain Modulation During Recovery From Whiplash-associated Disorders.

The objective of this study was to investigate the pain-sensory profile of patients with whiplash-associated disorders (WADs) prior and post 2 weeks of standardized rehabilitation and after a 6-month follow-up. Twenty-two WAD participants (grade II; 14 women) and 22 sex-matched and age-matched healthy pain-free controls were enrolled. Pressure pain thresholds (PPTs) were assessed at local and distal muscles. Conditioned pain modulation (CPM) of PPTs was assessed using cuff pressure around the upper arm. Referred area of pain following supra-threshold pressure stimulation of the infraspinatus muscle was recorded on a body chart. Psychometric variables (pain intensity, area of perceived pain, pain catastrophizing, kinesiophobia, sleep problems, and depression level) were assessed. WAD group additionally completed the Neck Disability Index. The WAD group demonstrated lower local PPTs compared with controls at all time points (P<0.05) and lower distal PPTs at baseline and at 2 weeks when compared with 6 months (within-group) (P<0.05). The WAD group had a reduced CPM response and larger induced referred pain areas compared with controls (P<0.05), while no within-group changes were observed at any time point. The WAD group reported higher pain intensity and perceived area of pain compared with controls at all time points (P<0.05) and a mean Neck Disability Index score of 41% at baseline, 16% at 2 weeks, and 4% at 6 months. Furthermore, the WAD group reported improvements in all other psychometric variables (P<0.05), although only pain catastrophizing levels were comparable to controls at 2 weeks. PPTs but not CPM improved in the WAD group and were comparable to controls following 2 weeks following standardized rehabilitation, indicating that normalization of CPM may not be required to recover from WAD.

Low Electrical Resistance Properties of Acupoints: Roles of NOergic Signaling Molecules and Neuropeptides in Skin Electrical Conductance.

Early studies from several independent laboratories demonstrated that acupoints possess the characteristics of low electrical resistance. New devices are developing to increase the reliability of electrical skin impedance measurements for counteracting the factors including skin dryness, skin thickness, size of the sensing electrode, pressure applied on the electrode, interelectrode distance, room temperature, and humidity. Morphological studies have identified that blood vessels, hair follicles, and nervous components are enhanced in the meridians/acupoints, which represent areas of potentially high neuronal activity. Recent evidence shows that nitric oxide (NO) concentrations are enhanced in skin acupoints/meridians. L-arginine-derived NO synthesis modifies skin norepinephrine (NE) synthesis/release in acupoints/meridians, and NO-NE activations play an important role in mediating the skin conductance responses to electrical stimulation. NOergic signaling molecules interact with gap junction and transient receptor potential vanilloid type-1. Other studies reported that the high conductance at acupoints is a result of the release of the neuropeptides substance P and calcitonin gene-related peptide during neurogenic inflammation in the referred pain area. Pathological body conditions caused considerable changes in skin conductance or impedance at acupoints. Although systematic research with an improved equipment and research design to avoid the influencing factors are requested for a definite answer in this field, the results from anatomical and biochemical studies consistently show that acupoints exist higher levels of nervous components, and NOergic signaling molecules and neuropeptides involved in the skin low resistance at acupoints. The increased interest in the acupoints/meridians has led to an open-minded attitude towards understanding this system, which is fundamental important to establish the valid aspects of scientific basis of Chinese medicine mechanisms and therapies.

Stimulation of Myofascial Trigger Points in the Sternocleidomastoid Evokes Facial Thermal Response Correlated with the Referred Pain

The purpose of this research is to identify and correlate the referred pain evocated by myofascial trigger points (TrPs) pressure pain threshold (PPT) in the sternocleidomastoid muscle using thermal infrared imaging (IR). Facial IR images of 46 volunteers (21 male and 25 female, average age 32 ± 6.3) undergoing PPT of five TrPs locations on the sternocleidomastoid belly were recorded. Each PPT lasted 10 s, with an interstimulus interval of 2 min. Sixteen thermal IR images were recorded for each subject: at baseline (t0), 2 s before PPT (t1), 2 s (t2) and 60 s (t3) after PPT of each TrPs location. During the interstimulus interval, subjects were asked to draw over a head–neck template displayed on a computer screen the areas of referred pain eventually evoked by the stimulation and the referred pain intensity by means of a Visual Analogue Scale (VAS). The VAS template was then superimposed with the IR records. Two temperature (T) variations were calculated: ΔT1 = T(t2) − T(t1) and ΔT2 = T(t3) − T(t1). Differences in ∆T range ≥ 0.2 °C have been considered significant. In 77% of the superimpositions, the referred pain area corresponded to a ΔT2 ≥ 0.2 °C while only the 59% corresponded to a ΔT1 ≥ 0.2 °C. In 19% of superimpositions, a ΔT2 ≥ 0.2 °C did not correspond to a referred pain area indicated by the patient, and this percentage lowers to 4% for ΔT1 ≥ 0.2 °C. None of the areas that reported a VAS of 0 or 1 showed a ΔT1 ≥ 0.2 °C or a ΔT2 ≥ 0.2 °C. Considering the limitations of this pilot study, IR could be used to identify referred pain evocated by TrPs on sternocleidomastoid muscle.

Patients with symptomatic permanent atrial fibrillation show quantitative signs of pain sensitisation

ObjectiveMost patients with atrial fibrillation (AF) report symptoms, while one-third are asymptomatic. We hypothesised that sensory processing, in particular pain, differs in patients with symptomatic and asymptomatic AF.MethodsThirty individuals with...

Electroacupuncture at Neurogenic Spots in Referred Pain Areas Attenuates Hepatic Damages in Bile Duct-Ligated Rats.

Visceral pain frequently produces referred pain at somatic sites due to the convergence of somatic and visceral afferents. In skin overlying the referred pain, neurogenic spots characterized by hyperalgesia, tenderness and neurogenic inflammation are found. We investigated whether neurogenic inflammatory spots function as acupoints in the rat model of bile duct ligation-induced liver injury. The majority of neurogenic spots were found in the dorsal trunk overlying the referred pain and matched with locations of acupoints. The spots, as well as acupoints, showed high electrical conductance and enhanced expression of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP). Electroacupuncture at neurogenic spots reduced serum hepatocellular enzyme activities and histological patterns of acute liver injury in bile duct ligation (BDL) rats. The results suggest that the neurogenic spots have therapeutic effects as acupoints on hepatic injury in bile-duct ligated rats.

The Area of Pressure-Induced Referred Pain Is Dependent on the Intensity of the Suprathreshold Stimulus: An Explorative Study.

To investigate the pain referral area (number of pixels) and extent (vector length) as elicited from increasing intensities of pressure-induced pain at the shoulder. Cross-sectional design. Clinical laboratory setting. Twenty-two healthy men and women participated in two experimental sessions. Delayed onset of muscle soreness (DOMS) was induced in the dominant shoulder and assessed 24hours later. Participants rated the level of DOMS on a 6-point Likert scale. Four different intensities (pressure pain threshold [PPT]+20%, PPT+30%, PPT+40%, and PPT+50%) were applied to the infraspinatus in a randomized, balanced fashion for 60seconds from low to high intensity or vice versa. The resulting location, area, and extent of referred pain as drawn by the participants on a digital body chart were extracted and expressed in pixels. The extent of pain was defined as the vector length extending from the ipsilateral earlobe to the most distal location of the pain. The referred pain area from PPT+20% was smaller than PPT+30%, PPT+40%, and PPT+50%. The extent of referred pain did not differ between the pressure pain intensities. Pressure intensity at PPT+30%, but no more, produces the greatest referred pain area as compared with the traditional pressure intensity of PPT+20%. Thus, the intensity of PPT+30% may be ideal for exploring the mechanisms of referred pain. The extent of the pain represents an independent expression of the intensity of the provoking stimulus and may be more closely related to the location of the stimulus.

Pressure-Induced Referred Pain as a Biomarker of Pain Sensitivity in Fibromyalgia

Fibromyalgia (FM) syndrome is characterized by widespread pain, fatigue, and generalized increased pain sensitivity. Appropriate and simple pain models are methods employed to assess pain mechanisms that can potentially lead to improved treatments. Pressure pain thresholds (PPTs) or mapping the referred pain area produced by pressure stimulation at suprathreshold intensities are used to assess pain mechanisms. The optimal suprathreshold stimulation intensity to elicit referred pain with minimal discomfort for patients with FM has yet to be determined. The aim of this study was to compare the area and intensity of pressure-induced referred pain in patients with FM as elicited by systematic increases in PPTs, compared with controls. Observational, crossed-section study. Research laboratory. Twenty-six patients with FM and 26 healthy controls, age- and gender-matched, were included. Suprathreshold stimulation was applied to the infraspinatus muscle of the dominant side at 4 different intensities (PPT +20%, +30%, +40%, and +50%), after which referred pain was evaluated by measuring the area of pain in pixels using a digital body chart and its intensity on a Visual Analog Scale. Factors related to anxiety condition, pain catastrophizing, depression, and quality of life were recorded. The referred pain areas were larger in the FM group compared with healthy individuals at 120% (P = 0.024), 130% (P = 0.001), 140% (P = 0.001), and 150% (P = 0.001) PPT, however, within the FM group no differences were found between the intensity of suprathreshold stimulation and the size of the referred pain areas (P = 0.135) or pain intensity (P > 0.05). There was a positive correlation between the size of referred pain areas and pain catastrophizing in the FM group (r = 0.457, P = 0.032). This study presents some limitations, among which is the variability found in the referred pain areas. These findings show that referred pain induced by applying a suprathreshold pressure of 120% PPT can be a useful biomarker to assess sensitized pain mechanisms in patients suffering from FM. Referred pain, pain sensitivity, fibromyalgia, central sensitization, suprathreshold, pressure pain threshold, biomarker, facilitated pain mechanisms.

Myofascial trigger point: an indicator of acupoint sensitization

The present study is to investigate the characteristic distribution of primary pain points and referred pain areas in patients with knee-joint pain diseases, therefore revealing the correlation between the myofascial trigger point and acupoint sensitization. A total of 483 patients (320 men and 163 women, 36 to 72 years in age) with knee-joint pain recruited from 4 clinical centers were observed from July, 2017 to April, 2019 in the present study. The areas of primary and referred pain in these patients were detected by thumb-pressing and marked on human anatomic atlas. Of the 483 enrolled participants, 336 had lesion sites or tender points around the injured knee joint, and 147 with myofascial pain syndrome showed referred pain spots (zones) in the knee joint area. In 105 patients with patellar tendonitis, epiphysitis of the tibial tubero-sity, or quadriceps tendonitis, the pain area was mainly distributed in the anterior region of the knee. In 76 patients with medial collateral ligament injury, medial meniscal lesion, goose foot bursitis or semimembranosus ending-point inflammation, the pain points mainly occurred in the medial area of the knee. In 127 patients with lateral collateral ligament, lateral meniscus lesion, iliotibial band tendonitis, popliteus or triceps tendinitis, the pain spots were found in the lateral region of the knee. In 28 patients with posterior cruciate ligament injury or popliteal fossa tendonitis, the local pain was found to be at the back of the knee. Referred pain areas were normally detected in the lateral femoral muscles (43 cases), anterior femoral muscles (39 cases), adductor group of femur (26 cases), posterior popliteal fossa muscles group (15 cases), hamstrings (13 cases) and medial leg (11 cases)．. The primary pain areas or spots of the knee injury mainly distribute around the joint, whereas those of each muscle group lesion are often located in their respective skeletal muscle. Most of the referred pain areas often occur in the distal end of skeletal muscle and around the knee joint. Primary myofascial trigger points may be considered to be an indicator of acupoint sensitization.

Co-occurrence of pain syndromes.

Many pain conditions in patients tend to co-occur, influencing the clinical expressions of each other in various ways. This paper summarizes the main concurrent pain conditions by analyzing the major interactions observed. In particular, co-occurrence will be examined in: visceral pain (especially ischemic heart disease, irritable bowel syndrome, dysmenorrhea/endometriosis and urinary pain), fibromyalgia, musculoskeletal pain and headache. Two concurrent visceral pains from internal organs sharing at least part of their central sensory projection can give rise to viscero-visceral hyperalgesia, i.e., enhancement of typical pain symptoms from both districts. Visceral pain, headache and musculoskeletal pains (myofascial pain from trigger points, joint pain) can enhance pain and hyperalgesia from fibromyalgia. Myofascial pain from trigger points can perpetuate pain symptoms from visceral pain conditions and trigger migraine attacks when located in the referred pain area from an internal organ or in cervico-facial areas, respectively. The pathophysiology of these pain associations is complex and probably multifactorial; among the possible processes underlying the mutual influence of symptoms recorded in the associations is modulation of central sensitization phenomena by nociceptive inputs from one or the other condition. A strong message in these pain syndrome co-occurrence is that effective treatment of one of the conditions can also improve symptoms from the other, thus suggesting a systematic and thorough evaluation of the pain patient for a global effective management of his/her suffering.

Los neuropéptidos SP y CGRP subyacen en las propiedades eléctricas de los puntos de acupuntura

Electrical skin measurements at acupuncture points (acupoints) have been utilized as a diagnostic and therapeutic aid for more than 50 years. Although acupoints are described as having distinct electrical properties, such as high conductance and low impedance, the underlying mechanisms are currently unknown. The present study investigated in a rat model of hypertension whether the high conductance at acupoints is a result of the release of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) during neurogenic inflammation in the referred pain area. When plasma extravasation from neurogenic inflammation was examined by exploring the leakage of intravenously injected Evans blue dye (EBD) to the skin, extravasated EBD was found most frequently in acupoints on the wrist. The increased conductance and temperature at these acupoints occurred during the development of hypertension. The increase in conductance and plasma extravasation at acupoints in hypertensive rats was ablated by cutting median and ulnar nerves, blocking small diameter afferent fibers with resiniferatoxin (RTX) injection into median and ulnar nerves, or antagonizing SP or CGRP receptors in acupoints. In turn, intradermal injection of SP or CGRP resulted in increased conductance and plasma extravasation in naïve rats. Elevated levels of SP and CGRP were found in the acupoints of hypertensive rats. These findings suggest that the high conductance at acupoints is due to vascular leakage following local release of SP and CGRP during neurogenic inflammation.

Neuropeptides SP and CGRP Underlie the Electrical Properties of Acupoints.

Electrical skin measurements at acupuncture points (acupoints) have been utilized as a diagnostic and therapeutic aid for more than 50 years. Although acupoints are described as having distinct electrical properties, such as high conductance and low impedance, the underlying mechanisms are currently unknown. The present study investigated in a rat model of hypertension whether the high conductance at acupoints is a result of the release of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) during neurogenic inflammation in the referred pain area. When plasma extravasation from neurogenic inflammation was examined by exploring the leakage of intravenously injected Evans blue dye (EBD) to the skin, extravasated EBD was found most frequently in acupoints on the wrist. The increased conductance and temperature at these acupoints occurred during the development of hypertension. The increase in conductance and plasma extravasation at acupoints in hypertensive rats was ablated by cutting median and ulnar nerves, blocking small diameter afferent fibers with resiniferatoxin (RTX) injection into median and ulnar nerves, or antagonizing SP or CGRP receptors in acupoints. In turn, intradermal injection of SP or CGRP resulted in increased conductance and plasma extravasation in naïve rats. Elevated levels of SP and CGRP were found in the acupoints of hypertensive rats. These findings suggest that the high conductance at acupoints is due to vascular leakage following local release of SP and CGRP during neurogenic inflammation.

Exploration of Quantitative Sensory Testing in Latent Trigger Points and Referred Pain Areas.

The objective of this study was to investigate somatosensory nerve fiber function by applying different quantitative sensory testing including thermal, mechanical, and vibration thresholds over latent trigger points (TrP) and in its associated referred pain area. A total of 20 patients with unilateral latent TrPs in the extensor carpi radialis brevis were included. Warmth detection threshold (WDT), cold detection threshold (CDT) and heat/cold pain thresholds (HPT, CPT), mechanical detection (MDT) and pain (MPT) thresholds, vibration threshold (VT), and pressure pain thresholds (PPT) were blinded assessed over the TrP, in the referred pain area, and in the respective contralateral mirror areas. A multilevel mixed-model ANOVA with site (TrP, referred pain area) and side (real or contralateral) as within-patient factors and sex as between-patients factor was conducted. No significant differences for thermal detection (WDT, CDT) or thermal pain thresholds (HPT, CPT) were found (all, Ps>0.141). The assessments over the TrP area showed lower PPT and MDT compared with the mirror contralateral TrP area (P<0.05). MDT were higher (P=0.001) but PPT (P<0.001) and MPT (P=0.032) were lower over the TrP area and contralateral mirror point compared with their respectively referred pain areas. Finally, VT was higher over the TrP area than in the referred pain area and over both mirror contralateral points. Assessing sensory changes over latent myofascial TrPs reveal mechanical hyperesthesia, pressure pain hyperalgesia, and vibration hypoesthesia compared with a contralateral mirror area.

Pressure-induced referred pain areas are more expansive in individuals with a recovered fracture.

Musculoskeletal trauma and pain can sensitize central pain mechanisms, but whether these normalize on recovery is unknown. This study compared the extent of pain referral in individuals recovered from a musculoskeletal trauma and healthy controls. Twenty pain-free participants recovered from a shoulder fracture and 20 age-/sex-matched controls participated in 2 experimental sessions (day-0 and day-1) separated by 24 hours. On both days, pressure pain thresholds were measured bilaterally at infraspinatus, supraspinatus, trapezius, and gastrocnemius muscles. Referred pain towards the shoulder region was induced by a 60-second pressure stimulation (pressure pain threshold + 20%) at the infraspinatus muscle and recorded on an electronic body chart. After day-0 assessments, delayed onset muscle soreness (DOMS) was induced to challenge the pain systems by exercising the external rotators of the recovered/dominant shoulder. The size of pressure-induced pain referral on day-0 did not differ between groups, although there was a tendency for a smaller referred pain area in recovered group. Pressure pain thresholds at the infraspinatus muscle on the DOMS side were reduced on day-1 in both groups (P = 0.03). An expansion of pressure-induced pain referral was found in both groups following the DOMS protocol on day-1 (P = 0.05) with a relatively larger expansion (P = 0.05) and higher frequency of pain in the shoulder (P = 0.04) in the recovered pain group. After complete recovery and absence of pain symptoms after a fracture, central pain mechanisms seem to normalize in the region of the trauma after recovery but when sensitized a heightened response can emerge. Such mechanisms could be important for recurrence of pain conditions.

Pressure-induced referred pain is expanded by persistent soreness.

Several chronic pain conditions are accompanied with enlarged referred pain areas. This study investigated a novel method for assessing referred pain. In 20 healthy subjects, pressure pain thresholds (PPTs) were recorded and pressure stimuli (120% PPT) were applied bilaterally for 5 and 60 seconds at the infraspinatus muscle to induce local and referred pain. Moreover, PPTs were measured bilaterally at the shoulder, neck, and leg before, during, and after hypertonic saline-induced referred pain in the dominant infraspinatus muscle. The pressure and saline-induced pain areas were assessed on drawings. Subsequently, delayed onset muscle soreness was induced using eccentric exercise of the dominant infraspinatus muscle. The day-1 assessments were repeated the following day (day 2). Suprathreshold pressure stimulations and saline injections into the infraspinatus muscle caused referred pain to the frontal aspect of the shoulder/arm in all subjects. The 60-second pressure stimulation caused larger referred pain areas compared with the 5-second stimulation (P < 0.01). Compared with pressure stimulation, the saline-induced referred pain area was larger (P < 0.02). After saline-induced pain, the PPTs at the infraspinatus and supraspinatus muscles were reduced (P < 0.05), and the 5-second pressure-induced referred pain area was larger than baseline. Pressure pain thresholds at the infraspinatus and supraspinatus muscles were reduced at day 2 in the delayed onset muscle soreness side (P < 0.05). Compared with day 1, larger pressure and saline-induced referred pain areas were observed on day 2 (P < 0.05). Referred pain to the shoulder/arm was consistently induced and enlarged after 1 day of muscle soreness, indicating that the referred pain area may be a sensitive biomarker for sensitization of the pain system.

Is Extracorporeal Shock Wave Therapy Effective in the Treatment of Myofascial Pain Syndrome?

Background: Extracorporeal shock wave therapy (ESWT) is one of the treatment options used for patients with myofascial pain syndrome (MPS), although its effectiveness is controversial. The purpose of this study was to evaluate the effectiveness of ESWT in the treatment of MPS in terms of pain relief and functional improvements. Methods: We assessed 93 patients with MPS who underwent ESWT from March 2009 to July 2014. After exclusion of 25 patients with shoulder diseases, 68 patients were enrolled in the study. The mean follow-up period was 7.5 months (± 4.2 weeks), and the average duration of symptoms was 5 months (range, 2–16 months). ESWT was applied to intramuscular taut bands and referred pain areas once a week for 3 weeks. Visual analog scale (VAS) pain scores and American Shoulder and Elbow Surgeons (ASES) scores were obtained at an initial assessment and at the 6-week, 3-month, and 6-month follow-up assessments. Results: VAS pain scores and ASES scores improved significantly after 3 sessions of ESWT (p 0.05). Conclusions: ESWT is an effective treatment option for patients with MPS.