The beneficial effects of the herbal medicine Di-huang-yin-zi (DHYZ) on patients with ischemic stroke: A Randomized, Placebo controlled clinical study.

OBJECTIVES: This study aimed to investigate the safety and therapeutic efficacy of herbal drug, Di Huang Yin Zi (DHYZ), in patients affected by ischemic stroke. METHODS: In this double blind, placebo-controlled study, a total of 100 patients with recent (less than 30 days) ischemic stroke were randomized to receive DHYZ or placebo for 12 weeks. Both groups also received rehabilitation therapy during the study period. As there were 13 dropouts, a total of 45 patients on DHYZ and 42 on placebo were available for analysis. The Fugl-Meyer Assessment (FMA) and Barthel index (BI) were assessed before treatment and at 4-week intervals. RESULTS: We observed that the FMA score and BI were increased, in both groups at week 4, 8 and 12 compared with the baseline. Furthermore, significantly better FMA score was observed in patients treated with DHYZ at week 8 and 12 (both P<0.05). BI was significantly higher in DHYZ group than in placebo group at weeks 12 (P<0.05). At week 12, the 95% Confidence Intervals (CI) of mean difference of FMA and BI also indicated that the differences between two groups were statistically significant. Compared to placebo, DHYZ produced significantly greater improvement in FMA grade at week 12 (44.4% versus 23.8%, χ(2)=4.09, P<0.05). CONCLUSIONS: DHYZ showed good efficacy, safety and tolerability in patients affected by ischemic stroke. We conclude that DHYZ may be a useful therapeutic option in patients with ischemic stroke.

A afferent fibers are involved in the pathology of central changes in the spinal dorsal horn associated with myofascial trigger spots in rats.

A afferent fibers have been reported to participate in the development of the central sensitization induced by inflammation and injuries. Current evidence suggests that myofascial trigger points (MTrPs) induce central sensitization in the related spinal dorsal horn, and clinical studies indicate that A fibers are associated with pain behavior. Because most of these clinical studies applied behavioral indexes, objective evidence is needed. Additionally, MTrP-related neurons in dorsal root ganglia and the spinal ventral horn have been reported to be smaller than normal, and these neurons were considered to be related to A fibers. To confirm the role of A fibers in MTrP-related central changes in the spinal dorsal horn, we studied central sensitization as well as the size of neurons associated with myofascial trigger spots (MTrSs, equivalent to MTrPs in humans) in the biceps femoris muscle of rats and provided some objective morphological evidence. Cholera toxin B subunit-conjugated horseradish peroxidase was applied to label the MTrS-related neurons, and tetrodotoxin was used to block A fibers specifically. The results showed that in the spinal dorsal horn associated with MTrS, the expression of glutamate receptor (mGluR1α/mGluR5/NMDAR1) increased, while the mean size of MTrS-related neurons was smaller than normal. After blocking A fibers, these changes reversed to some extent. Therefore, we concluded that A fibers participated in the development and maintenance of the central sensitization induced by MTrPs and were related to the mean size of neurons associated with MTrPs in the spinal dorsal horn.

Myelinated Afferents Are Involved in Pathology of the Spontaneous Electrical Activity and Mechanical Hyperalgesia of Myofascial Trigger Spots in Rats.

Myofascial trigger points (MTrPs) are common causes for chronic pain. Myelinated afferents were considered to be related with muscular pain, and our clinical researches indicated they might participate in the pathology of MTrPs. Here, we applied myofascial trigger spots (MTrSs, equal to MTrPs in human) of rats to further investigate role of myelinated afferents. Modified pyridine-silver staining revealed more nerve endings at MTrSs than non-MTrSs (P < 0.01), and immunohistochemistry with Neurofilament 200 indicated more myelinated afferents existed in MTrSs (P < 0.01). Spontaneous electrical activity (SEA) recordings at MTrSs showed that specific block of myelinated afferents in sciatic nerve with tetrodotoxin (TTX) led to significantly decreased SEA (P < 0.05). Behavioral assessment showed that mechanical pain thresholds (MPTs) of MTrSs were lower than those of non-MTrSs (P < 0.01). Block of myelinated afferents by intramuscular TTX injection increased MPTs of MTrSs significantly (P < 0.01), while MPTs of non-MTrSs first decreased (P < 0.05) and then increased (P > 0.05). 30 min after the injection, MPTs at MTrSs were significantly lower than those of non-MTrSs (P < 0.01). Therefore, we concluded that proliferated myelinated afferents existed at MTrSs, which were closely related to pathology of SEA and mechanical hyperalgesia of MTrSs.

Mechanistic experimental pain assessment in computer users with and without chronic musculoskeletal pain.

BACKGROUND: Musculoskeletal pain from the upper extremity and shoulder region is commonly reported by computer users. However, the functional status of central pain mechanisms, i.e., central sensitization and conditioned pain modulation (CPM), has not been investigated in this population. The aim was to evaluate sensitization and CPM in computer users with and without chronic musculoskeletal pain. METHODS: Pressure pain threshold (PPT) mapping in the neck-shoulder (15 points) and the elbow (12 points) was assessed together with PPT measurement at mid-point in the tibialis anterior (TA) muscle among 47 computer users with chronic pain in the upper extremity and/or neck-shoulder pain (pain group) and 17 pain-free computer users (control group). Induced pain intensities and profiles over time were recorded using a 0-10 cm electronic visual analogue scale (VAS) in response to different levels of pressure stimuli on the forearm with a new technique of dynamic pressure algometry. The efficiency of CPM was assessed using cuff-induced pain as conditioning pain stimulus and PPT at TA as test stimulus. RESULTS: The demographics, job seniority and number of working hours/week using a computer were similar between groups. The PPTs measured at all 15 points in the neck-shoulder region were not significantly different between groups. There were no significant differences between groups neither in PPTs nor pain intensity induced by dynamic pressure algometry. No significant difference in PPT was observed in TA between groups. During CPM, a significant increase in PPT at TA was observed in both groups (P < 0.05) without significant differences between groups. For the chronic pain group, higher clinical pain intensity, lower PPT values from the neck-shoulder and higher pain intensity evoked by the roller were all correlated with less efficient descending pain modulation (P < 0.05). CONCLUSIONS: This suggests that the excitability of the central pain system is normal in a large group of computer users with low pain intensity chronic upper extremity and/or neck-shoulder pain and that increased excitability of the pain system cannot explain the reported pain. However, computer users with higher pain intensity and lower PPTs were found to have decreased efficiency in descending pain modulation.

Myofascial trigger points in patients with whiplash-associated disorders and mechanical neck pain.

OBJECTIVE: The aim of this study was to investigate pain patterns and the distribution of myofascial trigger points (MTPs) in whiplash-associated disorders (WADs II and III) as compared with mechanical neck pain (MNP). METHODS: Manual examination of suboccipital, upper trapezius, elevator scapula, temporalis, supraspinatus, infraspinatus, deltoid, and sternocleidomastoid muscles, was done to search for the presence of both active or latent MTPs in 49 WAD patients and 56 MNP patients. Local pain and referred pain from each active MTP was recorded on an anatomical map. RESULTS: The mean number of active MTPs was significantly greater in the WAD group (6.71 ± 0.79) than in the MNP group (3.26 ± 0.33) (P < 0.001), but this was not found for the latent MTPs (3.95 ± 0.57 vs. 2.82 ± 0.34; P > 0.05). In the WAD group, the current pain intensity (visual analogue scale) of the patients was significantly correlated with the number of active MTPs (rs = 0.03, P = 0.03) and the spontaneous pain area (rs = 0.25, P = 0.07), and the number of active MTPs was significantly correlated with the spontaneous pain area (rs = 0.3, P = 0.03). In the MNP group, significant correlation was found only between pain duration and spontaneous pain area (rs = 0.29, P = 0.02). CONCLUSIONS: Active MTPs are more prominent in WAD than MNP and related to current pain intensity and size of the spontaneous pain distribution in whiplash patients. This may underlie a lower degree of sensitization in MNP than in WAD.

Latent myofascial trigger points are associated with an increased intramuscular electromyographic activity during synergistic muscle activation.

UNLABELLED: The aim of this study was to evaluate intramuscular muscle activity from a latent myofascial trigger point (MTP) in a synergistic muscle during isometric muscle contraction. Intramuscular activity was recorded with an intramuscular electromyographic (EMG) needle inserted into a latent MTP or a non-MTP in the upper trapezius at rest and during isometric shoulder abduction at 90° performed at 25% of maximum voluntary contraction in 15 healthy subjects. Surface EMG activities were recorded from the middle deltoid muscle and the upper, middle, and lower parts of the trapezius muscle. Maximal pain intensity and referred pain induced by EMG needle insertion and maximal pain intensity during contraction were recorded on a visual analog scale. The results showed that higher visual analog scale scores were observed following needle insertion and during muscle contraction for latent MTPs than non-MTPs (P < .01). The intramuscular EMG activity in the upper trapezius muscle was significantly higher at rest and during shoulder abduction at latent MTPs compared with non-MTPs (P < .001). This study provides evidence that latent MTPs are associated with increased intramuscular, but not surface, EMG amplitude of synergist activation. The increased amplitude of synergistic muscle activation may result in incoherent muscle activation pattern of synergists inducing spatial development of new MTPs and the progress to active MTPs. PERSPECTIVE: This article presents evidence of increased intramuscular, but not surface, muscle activity of latent MTPs during synergistic muscle activation. This incoherent muscle activation pattern may overload muscle fibers in synergists during muscle contraction and may contribute to spatial pain propagation.

Hyperexcitability to electrical stimulation and accelerated muscle fatiguability of taut bands in rats.

OBJECTIVE: Myofascial trigger points contribute significantly to musculoskeletal pain and motor dysfunction and may be associated with accelerated muscle fatiguability. The aim of this study was to investigate the electrically induced force and fatigue characteristics of muscle taut bands in rats. METHODS: Muscle taut bands were dissected out and subjected to trains of electrical stimulation. The electrical threshold intensity for muscle contraction and maximum contraction force (MCF), electrical intensity dependent fatigue and electrical frequency dependent fatigue characteristics were assessed in three different sessions (n=10 each) and compared with non-taut bands in the biceps femoris muscle. RESULTS: The threshold intensity for muscle contraction and MCF at the 10th, 15th and 20th intensity dependent fatigue stimuli of taut bands were significantly lower than those of non-taut bands (all p<0.05). The MCF at the 15th and 20th intensity dependent fatigue stimuli of taut bands were significantly lower than those at the 1st and 5th stimuli (all p<0.01). The MCF in the frequency dependent fatigue test was significantly higher and the stimulus frequency that induced MCF was significantly lower for taut bands than for non-taut bands (both p<0.01). CONCLUSIONS: The present study demonstrates that the muscle taut band itself was more excitable to electrical stimulation and significantly less fatigue resistant than normal muscle fibres.

Computer work and self-reported variables on anthropometrics, computer usage, work ability, productivity, pain, and physical activity.

BACKGROUND: Computer users often report musculoskeletal complaints and pain in the upper extremities and the neck-shoulder region. However, recent epidemiological studies do not report a relationship between the extent of computer use and work-related musculoskeletal disorders (WMSD).The aim of this study was to conduct an explorative analysis on short and long-term pain complaints and work-related variables in a cohort of Danish computer users. METHODS: A structured web-based questionnaire including questions related to musculoskeletal pain, anthropometrics, work-related variables, work ability, productivity, health-related parameters, lifestyle variables as well as physical activity during leisure time was designed. Six hundred and ninety office workers completed the questionnaire responding to an announcement posted in a union magazine. The questionnaire outcomes, i.e., pain intensity, duration and locations as well as anthropometrics, work-related variables, work ability, productivity, and level of physical activity, were stratified by gender and correlations were obtained. RESULTS: Women reported higher pain intensity, longer pain duration as well as more locations with pain than men (P < 0.05). In parallel, women scored poorer work ability and ability to fulfil the requirements on productivity than men (P < 0.05). Strong positive correlations were found between pain intensity and pain duration for the forearm, elbow, neck and shoulder (P < 0.001). Moderate negative correlations were seen between pain intensity and work ability/productivity (P < 0.001). CONCLUSIONS: The present results provide new key information on pain characteristics in office workers. The differences in pain characteristics, i.e., higher intensity, longer duration and more pain locations as well as poorer work ability reported by women workers relate to their higher risk of contracting WMSD. Overall, this investigation confirmed the complex interplay between anthropometrics, work ability, productivity, and pain perception among computer users.

Effects of colchicine-induced microtubule depolymerization on TRPV4 in rats with chronic compression of the dorsal root ganglion.

The aim of this study was to investigate the effect of colchicine-induced microtubule depolymerization on allodynia in rats with chronic compression of the dorsal root ganglion (DRG) (CCD) and the effect of colchicine on transient receptor potential vanilloid 4 (TRPV4). Intrathecal administration of the anti-microtubule agent, colchicine, resulted in a dose-dependent and partial reduction in CCD-induced mechanical and thermal allodynia. The reduction of allodynia was associated with significant and dose-dependent decreases in the levels of both TRPV4 mRNA and protein expression in CCD rats. In addition, colchicine resulted in reduction and advance of TRPV4 currents in both DRG neurons and HEK293-TRPV4 cells. The current-voltage (IV) relation in HEK293-TRPV4 cells that were exposed to colchicine displayed a typical outward rectification characteristic of TRPV4 with the reversal potential shifted toward a more positive voltage. In conclusion, intrathecal administration of colchicine attenuated allodynia and TRPV4 contributed to the colchicine-induced attenuation of allodynia in CCD rats.

Accelerated muscle fatigability of latent myofascial trigger points in humans.

OBJECTIVE: Muscle fatigue is prevalent in acute and chronic musculoskeletal pain conditions in which myofascial trigger points (MTPs) are involved. The aim of this study was to investigate the association of latent MTPs with muscle fatigue. DESIGN: Intramuscular electromyographic (EMG) recordings were obtained from latent MTPs and non-MTPs together with surface EMG recordings from the upper trapezius muscles during sustained isometric muscle contractions in 12 healthy subjects. OUTCOME MEASURES: Normalized root mean square (RMS) EMG amplitude and mean power frequency (MNF) were analyzed. The rate of perceived exertion and pain intensity from MTP side and non-MTP side were recorded. RESULTS: Pain intensity on the MTP side was significantly higher than the non-MTP side (P < 0.05). Intramuscular EMG from latent MTPs showed an early onset of decrease in MNF and a significant decrease at the end of fatiguing contraction as compared with non-MTPs (P < 0.05). Surface EMG from muscle fibers close to latent MTPs presented with an early onset of the increase in RMS amplitude and the increase was significantly higher than that from non-MTPs at the end of sustained isometric contraction (P < 0.05). CONCLUSIONS: A latent MTP is associated with an accelerated development of muscle fatigue and simultaneously overloading active motor units close to an MTP. Elimination of latent MTPs and inactivation of active MTPs may effectively reduce accelerated muscle fatigue and prevent overload spreading within a muscle.

Spatial pain propagation over time following painful glutamate activation of latent myofascial trigger points in humans.

UNLABELLED: The aim of this present study was to test the hypothesis that tonic nociceptive stimulation of latent myofascial trigger points (MTPs) may induce a spatially enlarged area of pressure pain hyperalgesia. Painful glutamate (.2 mL, 1M) stimulation of latent MTPs and non-MTPs in the forearm was achieved by an electromyography-guided procedure. Pain intensity (as rated on the visual analog scale [VAS]) and referred pain area following glutamate injections were recorded. Pressure pain threshold (PPT) was measured over 12 points in the forearm muscles and at the mid-point of tibialis anterior muscle before and at .5 hour, 1 hour, and 24 hours after glutamate injections. The results showed that maximal pain intensity, the area under the VAS curve, and referred pain area were significantly higher and larger following glutamate injection into latent MTPs than non-MTPs (all, P < .05). A significantly lower PPT level was detected over time after glutamate injection into latent MTPs at .5 hour (at 4 points), 1 hour (at 7 points), and 24 hours (at 6 points) in the forearm muscles. However, a significantly lower PPT was observed only at 24 hours after glutamate injection into non-MTPs in the forearm muscles (at 4 points, P < .05) when compared to the pre-injection PPT. PPT at the mid-point of the tibialis anterior was significantly decreased at 1 hour only as compared to the pre-injection PPT in both groups (< .05). The results of the present study indicate that nociceptive stimulation of latent MTPs is associated with an early onset of locally enlarged area of mechanical hyperalgesia. PERSPECTIVE: This study shows that MTPs are associated with an early occurrence of a locally enlarged area of pressure hyperalgesia associated with spreading central sensitization. Inactivation of MTPs may prevent spatial pain propagation.

Interaction of transient receptor potential vanilloid 4 with annexin A2 and tubulin beta 5.

The aim of the present study was to investigate if there exists an interaction of TRPV4 with annexin A2 and with tubulin beta 5 in transfected human embryonic kidney (HEK293) cells in vitro. Coimmunoprecipitation of the rat dorsal root ganglion was performed to validly conform the interaction of TRPV4 with the other two proteins. Gene fragments coding for the amino acids in protein were obtained. We conducted coimmunoprecipitation and immunofluorescence on the transfected cell samples. Coimmunoprecipitation experiments of transfected HEK293 cells revealed that TRPV4 and tubulin beta 5 associated together in a complex, whereas TRPV4 and annexin A2 did not. The immunofluorescence microscopy revealed a colocalization of TRPV4 with both the tubulin beta 5 and annexin A2. These results indicate an interaction between TRPV4 and tubulin beta 5 by associating together. However, the association between TRPV4 and annexin A2 may be mediated by some intermediate elements or just exists in some physiological conditions. Thus, TRPV4 channel function may be modulated by tubulin beta 5 and annexin A2 and their interactions may play a role in the mechanosensation in the pathogenesis of neuropathic pain.

Latent myofascial trigger points are associated with an increased antagonistic muscle activity during agonist muscle contraction.

UNLABELLED: The aim of this study was to evaluate motor unit activity from a latent myofascial trigger point (MTP) in an antagonist muscle during isometric agonist muscle contraction. Intramuscular activity was recorded with an intramuscular electromyographic (EMG) needle inserted into a latent MTP or a non-MTP in the posterior deltoid muscle at rest and during isometric shoulder flexion performed at 25% of maximum voluntary contraction in 14 healthy subjects. Surface EMGs were recorded from the anterior and posterior deltoid muscles. Maximal pain intensity and referred pain induced by EMG needle insertion were recorded on a visual analogue scale. The results showed that higher local pain was observed following needle insertion into latent MTPs (4.64 ± .48 cm) than non-MTPs (2.35 ± .43 cm, P < .005). Referred pain was reported in 6/14 subjects following needle insertion into latent MTPs, but none into the non-MTPs. The intramuscular EMG activity, but not surface EMG activity, in the antagonist muscle was significantly higher at rest and during shoulder flexion at latent MTPs than non-MTPs (P < .05). The current study provides the first evidence that increased motor unit excitability is associated with reduced antagonist reciprocal inhibition. PERSPECTIVE: This study shows that MTPs are associated with reduced efficiency of reciprocal linhibition, which may contribute to the delayed and incomplete muscle relaxation following exercise, disordered fine movement control, and unbalanced muscle activation. Elimination of latent MTPs and/or prevention of latent MTPs from becoming active may improve motor functions.

Latent myofascial trigger points.

A latent myofascial trigger point (MTP) is defined as a focus of hyperirritability in a muscle taut band that is clinically associated with local twitch response and tenderness and/or referred pain upon manual examination. Current evidence suggests that the temporal profile of the spontaneous electrical activity at an MTP is similar to focal muscle fiber contraction and/or muscle cramp potentials, which contribute significantly to the induction of local tenderness and pain and motor dysfunctions. This review highlights the potential mechanisms underlying the sensory-motor dysfunctions associated with latent MTPs and discusses the contribution of central sensitization associated with latent MTPs and the MTP network to the spatial propagation of pain and motor dysfunctions. Treating latent MTPs in patients with musculoskeletal pain may not only decrease pain sensitivity and improve motor functions, but also prevent latent MTPs from transforming into active MTPs, and hence, prevent the development of myofascial pain syndrome.

Nuclear factor-kappa B mediates TRPV4-NO pathway involved in thermal hyperalgesia following chronic compression of the dorsal root ganglion in rats.

The aim of this study was to test the hypothesis that nuclear factor-kappa B (NF-κB) is involved in TRPV4-NO pathway in thermal hyperalgesia following chronic compression of the dorsal root ganglion (DRG) (the procedure hereafter termed CCD) in rat. Intrathecal administration of two NF-κB inhibitors, pyrrolidine dithiocarbamate (PDTC; 10(-1) to 10(-2)M) and BAY (100-50 µM), both induced significantly dose-dependent increase in the paw withdrawal latency (PWL) and decrease in nitric oxide (NO) content in DRG when compared with control rats. Pretreatment with 4α-phorbol 12,13-didecanoate (4α-PDD, transient receptor potential vanilloid 4 (TRPV4) synthetic activator, 1 nm) attenuated the suppressive effects of PDTC (10(-1)M) and BAY (100 µM) on CCD-induced thermal hyperalgesia and NO production. In addition, Western blot analysis indicated that CCD rats exhibited nuclear NF-κB protein expression and low levels of cytoplasmic inhibitory-kappa B (I-κB) expression; the increase in NF-κB expression and decrease in I-κB expression were reversed after intrathecal injection of PDTC. In conclusion, our data suggested that NF-κB could be involved in TRPV4-NO pathway in CCD-induced thermal hyperalgesia.

Multiple active myofascial trigger points reproduce the overall spontaneous pain pattern in women with fibromyalgia and are related to widespread mechanical hypersensitivity.

OBJECTIVES: To determine whether the local and referred pain from active myofascial trigger points (MTrPs) reproduce the overall spontaneous fibromyalgia syndrome (FMS) pain pattern and whether widespread pressure hypersensitivity is related to the presence of widespread active MTrPs in FMS. METHODS: Forty-four women with FMS (mean age: 47±8 y) and 50 comparable healthy women (age: 48±7 y) participated in the study. MTrPs in the temporalis, masseter, upper trapezius, splenius capitis, sternocleidomastoid, suboccipital, levator scapulae, scalene, pectoralis major, extensor carpi radialis brevis, extensor digitorum communis, gluteus maximus, piriformis, vastus medialis, and tibialis anterior muscles were explored. Pressure pain thresholds over 18 tender points specified in the 1990 American College of Rheumatology for FMS were also assessed by an assessor blinded to the condition of the participants. RESULTS: The mean±SD number of MTrPs for each woman with FMS was 11±3, of which 10±2 were active MTrPs and the remaining 1±1 were latent. Healthy controls only had latent MTrPs (mean±SD: 2±1). The combination of the referred pain patterns from active MTrPs fully reproduced the overall spontaneous clinical pain area in patients with FMS. Patients with FMS had significant lower PPT compared with controls (P<0.001). Within FMS, a significant positive correlation was found between the number of active MTrPs and spontaneous pain intensity (rs=0.455; P=0.002). CONCLUSIONS: The local and referred pain elicited from widespread active MTrPs fully reproduced the overall spontaneous clinical pain area in patients with FMS. Widespread mechanical pain hypersensitivity was related to a greater number of active MTrPs. This study suggests that nociceptive inputs from active MTrPs may contribute to central sensitization in FMS.

Myofascial trigger points: spontaneous electrical activity and its consequences for pain induction and propagation.

Active myofascial trigger points are one of the major peripheral pain generators for regional and generalized musculoskeletal pain conditions. Myofascial trigger points are also the targets for acupuncture and/or dry needling therapies. Recent evidence in the understanding of the pathophysiology of myofascial trigger points supports The Integrated Hypothesis for the trigger point formation; however unanswered questions remain. Current evidence shows that spontaneous electrical activity at myofascial trigger point originates from the extrafusal motor endplate. The spontaneous electrical activity represents focal muscle fiber contraction and/or muscle cramp potentials depending on trigger point sensitivity. Local pain and tenderness at myofascial trigger points are largely due to nociceptor sensitization with a lesser contribution from non-nociceptor sensitization. Nociceptor and non-nociceptor sensitization at myofascial trigger points may be part of the process of muscle ischemia associated with sustained focal muscle contraction and/or muscle cramps. Referred pain is dependent on the sensitivity of myofascial trigger points. Active myofascial trigger points may play an important role in the transition from localized pain to generalized pain conditions via the enhanced central sensitization, decreased descending inhibition and dysfunctional motor control strategy.

Reproduction of overall spontaneous pain pattern by manual stimulation of active myofascial trigger points in fibromyalgia patients.

INTRODUCTION: It has previously been reported that local and referred pain from active myofascial trigger points (MTPs) in the neck and shoulder region contribute to fibromyalgia (FM) pain and that the pain pattern induced from active MTPs can reproduce parts of the spontaneous clinical FM pain pattern. The current study investigated whether the overall spontaneous FM pain pattern can be reproduced by local and referred pain from active MTPs located in different muscles. METHODS: A spontaneous pain pattern in FM was recorded in 30 FM patients and 30 healthy subjects served as controls. Local and referred pain patterns induced from active (patients) and latent (controls) MTPs were recorded following manual stimulation. The existence of MTPs was confirmed by intramuscular electromyographical registration of spontaneous electrical activity. RESULTS: Local and referred pain areas induced from key active MTPs in FM were larger than pain areas from latent MTPs in healthy controls (P < 0.001), but were similar to the overall spontaneous FM pain area in FM (P > 0.05). The induced pain area was positively associated with current spontaneous pain intensity in FM (P < 0.01). The locations of key active MTPs in FM patients were found to have latent MTPs in healthy subjects. The muscles containing key active MTPs in FM are often observed in the muscles of extensor digitorum, trapezius, infraspinatus in the upper part of the body and of quadratus lumborum, gluteus medius in the lower part of the body. CONCLUSIONS: The overall spontaneous FM pain pattern can be reproduced by mechanical stimulation of active MTPs located in different muscles, suggesting that fibromyalgia pain is largely composed of pain arising from muscle pain and spasm. Targeting active MTPs and related perpetuating factors may be an important strategy in FM pain control. TRIAL REGISTRATION: ISRCTN ISRCTN43167547.

Referred pain areas of active myofascial trigger points in head, neck, and shoulder muscles, in chronic tension type headache.

SUMMARY: Our aim was to analyze the differences in the referred pain patterns and size of the areas of those myofascial trigger points (TrPs) involved in chronic tension type headache (CTTH) including a number of muscles not investigated in previous studies. Thirteen right handed women with CTTH (mean age: 38 ± 6 years) were included. TrPs were bilaterally searched in upper trapezius, sternocleidomastoid, splenius capitis, masseter, levator scapulae, superior oblique (extra-ocular), and suboccipital muscles. TrPs were considered active when both local and referred pain evoked by manual palpation reproduced total or partial pattern similar to a headache attack. The size of the referred pain area of TrPs of each muscle was calculated. The mean number of active TrPs within each CTTH patient was 7 (95% CI 6.2-8.0). A greater number (T = 2.79; p = 0.016) of active TrPs was found at the right side (4.2 ± 1.5) when compared to the left side (2.9 ± 1.0). TrPs in the suboccipital muscles were most prevalent (n = 12; 92%), followed by the superior oblique muscle (n =11/n = 9 right/left side), the upper trapezius muscle (n = 11/n = 6) and the masseter muscle (n = 9/n=7). The ANOVA showed significant differences in the size of the referred pain area between muscles (F = 4.7, p = 0.001), but not between sides (F = 1.1; p = 0.3): as determined by a Bonferroni post hoc analysis the referred pain area elicited by levator scapulae TrPs was significantly greater than the area from the sternocleidomastoid (p = 0.02), masseter (p = 0.003) and superior oblique (p = 0.001) muscles. Multiple active TrPs exist in head, neck and shoulder muscles in women with CTTH. The referred pain areas of TrPs located in neck muscles were larger than the referred pain areas of head muscles. Spatial summation of nociceptive inputs from multiple active TrPs may contribute to clinical manifestations of CTTH.

Prevalence of myofascial trigger points in fibromyalgia: the overlap of two common problems.

With the objective evidence of their existence, myofascial trigger points (MTrPs) contribute to an increasing number of chronic regional and widespread pain conditions. The widespread spontaneous pain pattern in fibromyalgia (FM) is a summation of multiple regional pains due to active MTrPs. A regional pain in FM is from local active MTrPs and/or referred from remote active MTrPs. Positive tender points specified in FM are MTrPs, either active or latent. Manual stimulation of active MTrPs located in the muscles in different body regions completely reproduced overall spontaneous FM pain pattern. Active MTrPs as tonic peripheral nociceptive input contribute tremendously to the initiation and maintenance of central sensitization, to the impairment of descending inhibition, to the increased excitability of motor units, and to the induction of sympathetic hyperactivity observed in FM. The considerable overlap of MTrPs and FM in pain characteristics and pathophysiology suggests that FM pain is largely due to MTrPs.