Is there enough evidence to use botulinum toxin injections for bruxism management? A systematic literature review.

OBJECTIVE: The objective of the study was to conduct a systematic review of the literature assessing the effects of botulinum toxin (BoNT-A) injections in the management of bruxism. MATERIALS AND METHODS: Search for articles involved the PubMed, Scopus, Web of Science, Embase, Cochrane, Scielo and Lilacs databases. Specific terms were used and the search carried out from 1980 to March 2016 by three independent researchers. Randomized controlled studies (RCTs), prospective and before-after studies that applied BoNT-A at the masseter and/or temporalis muscles were included. RESULTS: Three RCTs and two uncontrolled before-after studies out of 904 identified citations were included in this review. All five articles dealt with sleep bruxism and featured a small sample size. None of them was about awake bruxism. Two randomized clinical trials were double-blinded, with a control group using saline solution. Two studies used polysomnography/electromyography for sleep bruxism diagnosis, whilst others were based on history taking and clinical examination. All studies using subjective evaluations for pain and jaw stiffness showed positive results for the BoNT-A treatment. In contrast, the two studies using objective evaluations did not demonstrate any reduction in bruxism episodes, but a decrease in the intensity of muscles contractions. CONCLUSION: Despite the paucity of works on the topic, BoNT-A seems to be a possible management option for sleep bruxism, minimizing symptoms and reducing the intensity of muscle contractions, although further studies are necessary especially as far as the treatment indications for bruxism itself is concerned. CLINICAL RELEVANCE: BoNT-A has been increasingly diffused in dentistry over recent years, being also used for pain management in patients with bruxism. Nonetheless, there is no consensus about its effects in this disorder.

Use of onabotulinumtoxinA in post-traumatic oromandibular dystonia.

PURPOSE: Post-traumatic oromandibular dystonia (PTOD) is a disorder whose symptoms can include bruxism, muscle pain, and involuntary muscle contraction, among others. The use of onabotulinumtoxinA (ObT-A) is helpful in controlling the symptoms of patients with PTOD. The aim of this study was to evaluate the use of ObT-A in the treatment of PTOD. MATERIALS AND METHODS: In this prospective case-series study, the population consisted exclusively of patients diagnosed with PTOD, without distinction by age or gender, from January 2007 to December 2010. The patients were diagnosed with PTOD and treated with ObT-A infiltration (primary predictor) at the Department of Maxillofacial Surgery at the Hospital Clínico Mutual de Seguridad (Santiago, Chile). The primary outcome variables were bruxism, muscle pain, and involuntary muscle contraction. The data were obtained through questionnaires registered in tables at each control. Systat 13.1 was used for statistical analysis. The statistical test used to compare patients' evolution over time was the test of signs. RESULTS: Thirty male patients 18 to 65 years old diagnosed with PTOD were treated with ObT-A infiltrations. The signs and symptoms associated with oromandibular dystonia (bruxism, muscle pain, and involuntary muscle contraction) were decreased in all patients after ObT-A infiltrations. CONCLUSIONS: The positive results and the absence of complications recommend the use of the infiltration protocol presented in this study for the treatment of PTOD.

Electromyographic analysis of masseter and temporal muscles, bite force, masticatory efficiency in medicated individuals with schizophrenia and mood disorders compared with healthy controls.

This study aimed to comparatively analyse the electromyographic activity of the masseter and temporal muscles at rest and during mandible postural clinical conditions (right and left laterality, protrusion and maximum voluntary contraction), right and left maximum molar bite forces and the masticatory efficiency of individuals with schizophrenia or mood disorders - all medicated (medicated groups) compared with control group (healthy volunteers) via electromyography. Individuals were distributed into three groups: Group I (Schizophrenia - 20 individuals), Group II (mood disorders - 20 individuals) and Group III (Control - 40 individuals). Basically, the results were only statistically significant for the clinical mandible conditions and bite force. The most unsatisfactory results were observed in the medicated groups in relation to the control group. The group with mood disorders obtained the most unsatisfactory results compared with the group with schizophrenia. It was suggested by these observations that the association of mood disorders and schizophrenia with medication has negatively affected the stomatognathic system in relation to controls when the electromyography and bite force were used for the analysis.

Changes in masticatory function after injection of botulinum toxin type A to masticatory muscles.

This study examined changes in masticatory function after botulinum toxin type A (BTX-A) injection using objective and subjective tests during 12 weeks. Also, we compared differences in masticatory function between group in which only masseter muscle (M group) was injected and group in which masseter and temporal muscle (M-T group) were injected. Forty subjects were assigned into two groups; M group (n = 20) and the M-T group (n = 20). The Meditoxin(®) was used as BTX-A injection. The mixing ability index (MAI) was used as the objective indicator, and visual analogue scale (VAS) and food intake ability (FIA) index were used as subjective indicators. Overall, the masticatory function drastically declined after 4 weeks and gradually recovered with time. Compared with the pre-injection state, the masticatory function decreased by 89·2% (MAI), 12·2% (FIA) and 32·2% (VAS) 4 weeks after the injection (P < 0·05). When the results between M group and M-T group were compared, scores of VAS and FIA were significantly different 4 weeks after the injection (P < 0·05), but the MAI score showed no significant difference between two groups. In conclusion, this study showed that masticatory function was significantly decreased after BTX-A injection into the masticatory muscle after 4 and 8 weeks from injection. However, masticatory efficiency measured using MAI could completely recover after 12 weeks. Furthermore, after 8 weeks from the injection, the masticatory function measured after injection into only the masseter muscle was similar to that measured after injection into both masseter and temporal muscle.

Myofascial pain of the jaw muscles: comparison of short-term effectiveness of botulinum toxin injections and fascial manipulation technique.

A randomized controlled trial was performed to compare the short-term effectiveness of botulinum toxin injections and physiatric treatment provided by means of Fascial Manipulation techniques in the management of myofascial pain of jaw muscles. Thirty patients with a Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) diagnosis of myofascial pain were randomized to receive either single-session botulinum toxin injections (Group A) or multiple-session Fascial Manipulation (Group B). Maximum pain levels (VAS ratings) and jaw range of motion in millimeters (maximum mouth opening, protrusion, right and left laterotrusion) were assessed at baseline, at the end of treatment, and at a three-month follow-up. Both treatment protocols provided significant improvement over time for pain symptoms. The two treatments seem to be almost equally effective, Fascial Manipulation being slightly superior to reduce subjective pain perception, and botulinum toxin injections being slightly superior to increase jaw range of motion. Differences between the two treatment protocols as to changes in the outcome parameters at the three-months follow-up were not relevant clinically. Findings from the present investigation are in line with literature data supporting the effectiveness of a wide spectrum of conservative treatment approaches to myofascial pain of the jaw muscles. Future studies on larger samples over a longer follow-up span are needed on the way to identify tailored treatment strategies.

Modulation of exteroceptive suppression periods in human jaw-closing muscles by subanaesthetic dose of propofol.

Exteroceptive suppression (ES) periods in human jaw-closing muscles can be conditioned by a wide range of somatosensory stimuli and cognitive states. The aim of this study was to examine the effects of subanaesthetic doses of midazolam, ketamine and propofol on the short latency (ES1) and long latency (ES2) reflex in the jaw-closing muscles. First, we tried to evaluate the various methodological criteria for ES recording. We then examined the effect of subanaesthetic doses of midazolam (0·035 mg kg(-1)), ketamine (0·30 mg kg(-1)) and propofol (0·35 mg kg(-1)) on these reflexes of recording left masseter and temporalis muscle. ES duration did not differ greatly in the present study, recorded with the correct adjustment of stimulating and recording conditions. None of the subanaesthetic doses of the agents influenced ES1, and no significant effects on ES2 were observed with midazolam and ketamine. However, significant inhibitory change was observed in ES2 with propofol. ES2 is thought to be mediated by afferents, which descend in the spinal trigeminal tract and connect with a polysynaptic chain of excitatory interneurones located in the lateral reticular formation. Our observations indicate that propofol is uniquely effective not only through involvement of the gamma-aminobutyric acid type A receptor, but also through a range of other effects.

Bone changes in the mandible following botulinum neurotoxin injections.

In this study, botulinum neurotoxin type A (BoTx/A) was injected into the temporalis and masseter muscles of growing rats to induce masticatory hypoactivity. Sixty, 30-day-old, male Long-Evans rats were randomly divided into four groups. BoTx/A was bilaterally injected in the masseter muscles in group I, in the temporalis muscles in group II, and into both the masseter and the temporalis muscles in group III. Group IV served as the control in which saline was bilaterally injected into both muscles. Forty-five days after the injections, the rats were sacrificed. Observation of cortical bone thickness from bone biopsies of the right halves of the mandibles, evaluation of the volume of masseter and temporalis muscles with a plethysmometer, and scanning of bone mineral density (BMD) of the skull and mandibular bone structure with dual-energy X-ray absorptiometry were performed. One-way analysis of variance was employed to analyse measurements of muscle volume, BMD, and cortical bone thickness among the groups. The least square difference was then used to determine significance. Reduced cortical bone thickness and BMD of the skull and mandibular bone structure were observed. The volumes of the temporalis and masseter muscles injected with BoTx/A were smaller. Masticatory hypofunction affects bone structure during development.

[The effect of treatment of temporalis muscle fascia grafts with formaldehyde on the success rates of tympanoplasty]. / Temporal kas fasya greftlerinin formaldehit ile islenmesinin timpanoplasti basari oranlarina etkisi.

OBJECTIVES: This study aims to investigate the effect of formaldehyde treatment of temporalis muscle fascia grafts used during tympanoplasty on the postoperative success rates. PATIENTS AND METHODS: Fifty-four patients who underwent tympanoplasty between January 2006 and January 2007 in the Department of Otolaryngology, Medicine Faculty of Uludag University and who were under regular follow-up were included in this prospectively planned study and divided into two groups: the study group (n=24) and the control group (n=30). Temporal muscle fascia grafts were used in all patients. The grafts were treated with formaldehyde in the study group. All the controls of the patients were performed by otomicroscopy. Audiometric tests were performed at the 6th month controls. RESULTS: It was found out that perforation was permanently repaired in 79.2% of the study group and in 73.3% of the control group (p>0.05). We obtained an evident improvement in the average airway bone gap in both groups. We could not detect any statistical significance in the comparison of the operation duration between the groups although the operation duration in the study group was shorter (the study group: 735 seconds, the control group: 775 seconds). CONCLUSION: The formaldehyde treatment of the temporalis muscle fascial graft used in tympanoplasty was not superior in closing perforation and operation length compared to its direct dry use. However, we concluded that the graft could be more easily manipulated during the operation.

The effect of the Botulinum toxin-A on craniofacial development: an experimental study.

In this study, we developed a novel experimental model to evaluate muscular action on bone formation and remodeling by the help of Botulinum toxin-A (BTX). Forty-nine 15-day-old male Wistar rats were put into 4 groups randomly. Group 1 was the control group. BTX 0.4 IU (0.05 mL) was injected into the right masseter muscle in group 2 and into right temporalis muscle in group 3. The same volume of sterile saline was given into the both above-mentioned muscles in group 4. At the end of the fourth month, all animals were killed. Histology and weight of the masseter and temporalis muscles were studied. Thirty different osteometric measurements were also taken from skulls. Significant atrophy in BTX injected muscles was observed in groups 2 and 3. In group 4 (saline injection), only few osteometric measurements were significantly reduced, indicating the effect of the injection itself. Both groups 2 and 3 have apparent decrease in nasal bone, premaxilla, maxilla, and zygomatic dimensions on the injected side. When masseter group was compared with control and saline groups, no significant difference was found in skull base dimensions and mandibular length. In contrast, temporal group has also shown significant decrease in skull base dimensions. Our conclusions are as follows: (1) With this model, it is possible to study muscular action on bone formation and modeling without any surgical intervention, that is, by avoiding surgical artifacts, such as scar and contracture; (2) denervation of the skeletal muscles with BTX during the growing phase does effect bone development in a negative way; (3) pediatric use of the BTX deserves reevaluation under the light of these findings.

Evaluation of temporal muscle trophism in relation to the manipulation time and infiltration of 0.5% isobaric bupivacaine through a pterional approach. / Evaluación del trofismo del músculo temporal posquirúrgico en relación con el tiempo de manipulación y la infiltración transoperatoria de bupivacaína isobárica al 0,5% en pacientes sometidos a craneotomía pterional.

INTRODUCTION: There are different techniques for the reconstruction of the temporal muscle (TM) in the pterional approach (PA) in order to avoid and reduce atrophy, it has not been able to avoid it in its entirety. The administration of bupivacaine generates regeneration of muscle fibres. There are no studies in the medical literature that evaluate the time of TM manipulation and the use of bupivacaine for the treatment of atrophy after pterional approach, the present investigation aim is to describe the effects of these variables. PATIENT AND METHODS: Longitudinal study, including patients from 18-80 years old with pterional approach at 2016-2017. We evaluated the effects of the TM manipulation times and the administration of 0.5% bupivacaine on the trophism and function of TM. RESULTS: Twenty-nine patients underwent a PA; 16(55.17%) count with criteria for 0.5% bupivacain infiltration. We found a negative correlation between manipulation times and trophism, with no statistically significance (p>.05). We evaluated presurgical and postsurgical index of Helkimo and Fonseca's index, finding an increase of disfunction with statistically significance (p<.05). In patients who were infiltrated with 0.5% bupivacaine we observed a mean difference in the TM's trophism of 0.275±1.18mm, in contrast with no infiltrated which was 2.39±1.30mm (t[27] = -5.118, p=.0001). CONCLUSIONS: The manipulation of the TM during a pterional approach conditioned an impact on the quality of life according to the disfunction indexes, due to atrophy. This investigation exhibits that de administration of 0.5% bupivacaine during surgery offers a decrease in the TM atrophy.

Effect of botulinum toxin-A in myofascial pain patients with or without functional disc displacement.

PURPOSE: To evaluate the effects of botulinum toxin-A in the treatment of patients who have myofascial pain with or without functional disc displacement. PATIENTS AND METHODS: Twenty-four participants were randomly assigned to the study by using Research Diagnostic Criteria for Temporomandibular Disorders. All patients were informed about botulinum toxin-A, and were required to give informed consent. Before the injections, patients were asked to fill out a Biobehavioral Questionnaire to evaluate their pain and psychological status, and afterward, electromyography of the right and left masseter and anterior temporal muscles was recorded. Saline was injected into the masseter and anterior temporal muscles in the placebo group, and botulinum toxin-A was used in the study group. On days 14 and 28, patients were asked to fill out a Biobehavioral Questionnaire again, and electromyography of the right and left masseter and anterior temporal muscles was recorded again. RESULTS: The study group showed improvement in pain and psychological status. Although a decrease in the action potentials of the masseter muscles on day 14 was followed by an increase on day 28, the reduction of pain scores and improvement in psychological status continued on day 28. CONCLUSIONS: The injection of botulinum toxin-A decreases the muscle action potential in 14 days. The patients also show improvement in pain and psychological status.

Efficacy of botulinum toxin in treating myofascial pain in bruxers: a controlled placebo pilot study.

The present investigation is a preliminary double-blind, controlled placebo, randomized clinical trial with a six month follow-up period. The study aimed to assess the efficacy of type A botulinum toxin (Botox, Allergan, Inc. Irvine, CA) to treat myofascial pain symptoms and to reduce muscle hyperactivity in bruxers. Twenty patients (ten males, ten females; age range 25-45) with a clinical diagnosis of bruxism and myofascial pain of the masticatory muscles were enrolled in a double-blind, controlled placebo, randomized clinical trial, with a treatment group (ten subjects treated with botulinum toxin injections- BTX-A) and a control group (ten subjects treated with saline placebo injections). A number of objective and subjective clinical parameters (pain at rest and during chewing; mastication efficiency; maximum nonassisted and assisted mouth opening, protrusive and laterotrusive movements; functional limitation during usual jaw movements; subjective efficacy of the treatment; tolerance of the treatment) were assessed at baseline time and at one week, one month, and six months follow-up appointments. Descriptive analysis showed that improvements in both objective (range of mandibular movements) and subjective (pain at rest; pain during chewing) clinical outcome variables were higher in the Botox treated group than in the placebo treated subjects. Patients treated with BTX-A had a higher subjective improvement in their perception of treatment efficacy than the placebo subjects. Differences were not significant in some cases due to the small sample size. Results from the present study supported the efficacy of BTX-A to reduce myofascial pain symptoms in bruxers, and provided pilot data which need to be confirmed by further research using larger samples.

Effectiveness of botulinum toxin type A for the treatment of chronic masticatory myofascial pain: A case series.

BACKGROUND: The aim of this study is to evaluate the effectiveness of botulinum toxin type A (BTX-A) for the treatment of chronic masticatory myofascial pain (MMP) over 12 months and to test a standardized protocol. METHODS: This is a prospective case series of consecutive adult patients with chronic MMP treated with injection of BTX-A into the bilateral temporalis and masseter muscles. The authors used the same anatomic landmarks and dosage and followed each patient for 12 months. The primary outcome variables were reduction in pain measured with visual analog scale (VAS) and Physician Global Assessment (PGA). Secondary outcome variables were change in maximum pain-free opening, change in palpatory pain points in the face and oral cavity, and change in results from a questionnaire measuring disability, dysfunction, and psychosocial effects of the disease. RESULTS: The authors included 15 women and 4 men (mean [standard deviation] age, 32.7 [6.9] years) in the study. Pain decreased significantly as measured with the VAS (P < .0001) and PGA (P < .0001). Maximum pain-free opening increased significantly (P = .010), but maximum voluntary opening did not change significantly (P = .837). The number of palpatory pain points (P < .0001) and the symptom questionnaire score decreased over time (P < .0001). CONCLUSIONS: The results of this case series suggest that injecting BTX-A into the bilateral temporalis and masseter muscles may be a safe and effective treatment for chronic MMP. PRACTICAL IMPLICATIONS: Controlled clinical trials are needed to confirm whether administration of BTX-A is effective in treating facial pain.

Brain temperature effects of intravenous heroin: State dependency, environmental modulation, and the effects of dose.

Here we examined how intravenous heroin at a dose that maintains self-administration (0.1 mg/kg) affects brain temperature homeostasis in freely moving rats under conditions that seek to mimic some aspects of human drug use. When administered under standard laboratory conditions (quiet rest at 22 °C ambient temperature), heroin induced moderate temperature increases (1.0-1.5 °C) in the nucleus accumbens (NAc), a critical structure of the brain motivation-reinforcement circuit. By simultaneously recording temperatures in the temporal muscle and skin, we demonstrate that the hyperthermic effects of heroin results primarily from inhibition of heat loss due to strong and prolonged skin vasoconstriction. Heroin-induced brain temperature increases were enhanced during behavioral activation (i.e., social interaction) and in a moderately warm environment (29 °C). By calculating the "net" effects of the drug in these two conditions, we found that this enhancement results from the summation of the hyperthermic effects of heroin with similar effects induced by either social interaction or a warmer environment. When the dose of heroin was increased (to 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 mg/kg), brain temperature showed a biphasic down-up response. The initial temperature decrease was dose-dependent and resulted from a transient inhibition of intra-brain heat production coupled with increased heat loss via skin surfaces-the effects typically induced by general anesthetics. These initial inhibitory effects induced by large-dose heroin injections could be related to profound CNS depression-the most serious health complications typical of heroin overdose in humans.

Sensitivity of rat temporalis muscle afferent fibers to peripheral N-methyl-D-aspartate receptor activation.

The temporalis muscle is a common source of pain in headache and chronic craniofacial pain conditions such as temporomandibular disorders, which have an increased prevalence in women. The characteristics of slowly conducting temporalis afferent fibers have not been investigated. Therefore, the aim of the present study was to examine the characteristics of slowly conducting temporalis muscle afferent fibers and to determine whether these fibers are excited by activation of peripheral N-methyl-D-aspartate receptors. The response properties of a total of 117 temporalis afferent fibers were assessed in male and female rats. A majority of these fibers had high mechanical thresholds and slow conduction velocities (<10 m/s). The mechanical threshold of the temporalis afferent fibers was inversely correlated with afferent conduction velocity, however, no sex-related differences in mechanical threshold were identified. There were also no sex-related differences in N-methyl-D-aspartate-evoked afferent discharge. Indeed, injection of a high concentration (1600 mM) of N-methyl-D-aspartate into the temporalis muscle was necessary to evoke significant afferent discharge. Thirty minutes after the initial injection of N-methyl-D-aspartate into the temporalis muscle, a second injection of N-methyl-D-aspartate produced a response only about 50% as large as the initial injection. Co-injection of ketamine (20 mM) with the second injection of N-methyl-D-aspartate significantly decreased N-methyl-D-aspartate-evoked afferent discharge in both sexes. This concentration of ketamine is greater than that needed to attenuate afferent discharge evoked by injection of glutamate into the masseter muscle. These results suggest that unlike masseter afferent fibers, temporalis afferent fibers are relatively insensitive to peripheral N-methyl-D-aspartate receptor activation.

[Different types of injection in temporomandibular disorders (TMD) treatment]. / Les différents types d'injection pour traiter les dysfonctions de l'articulation temporomandibulaire.

INTRODUCTION: Intramuscular injections of botulinum toxin of type A (BoNTA) can release tension from masticatory and cervical muscles. Intra-articular injections relieve pain and sometimes diminish joint clicking and locking that occur during mouth opening. METHODS: Intramuscular injection of BoNTA is performed in our department since 2002. Injected muscles are masseter and temporal muscles. Later on, intra-articular injections of sodium hyaluronate were added, followed on a later stage by intra-articular injections of BoNTA for patients presenting with pain higher than 5/10 on an analogic visual scale. RESULTS: Eighty-five percent of the patients treated with intramuscular BoNTA injection improved. Total or partial pain relief was obtained in 95 % of the patients after intra-articular sodium hyaluronate injections. Seventy-six percent of the 56 patients treated by mean of intra-articular BoNTA injections improved, sometimes with a complete pain relief. DISCUSSION: These different techniques allow for good results, even if they do not represent a revolution in the treatment of temporomandibular disorders. In the hands of experienced practitioners, they have a low morbidity, are well accepted and are cost-effective.

Brain and body hyperthermia associated with heroin self-administration in rats.

Intravenous heroin self-administration in trained rats was accompanied by robust brain hyperthermia (+2.0-2.5 degrees C); parallel changes were found in the dorsal and ventral striatum, mediodorsal thalamus, and deep temporal muscle. Temperature began to increase at variable latency after a signal of drug availability, increased reliably (approximately 0.4 degrees C) before the first lever press for heroin, increased further (approximately 1.2 degrees C) after the first heroin injection, and rose more slowly after the second and third injections to stabilize at an elevated plateau (39-40 degrees C) for the remainder of the session. Brain and body temperature declined slowly when drug self-administration was terminated; naloxone precipitated a much more rapid decrease to baseline levels. Changes in temperature were similar across repeated daily sessions, except for the increase associated with the first self-administration of each session, which had progressively shorter latency and greater acceleration. Despite consistent biphasic fluctuations in movement activity associated with heroin self-administrations (gradual increase preceding the lever press, followed by an abrupt hypodynamia after drug infusion), mean brain temperature was very stable at an elevated plateau. Only mean muscle temperature showed evidence of biphasic fluctuations (+/-0.2 degrees C) that were time locked to and correlated with lever pressing and associated movements. Drug- and behavior-related changes in brain temperature thus appear to reflect some form of neuronal activation, and, because temperature is a factor capable of affecting numerous neural functions, it may be an important variable in the control of behavior by drugs of abuse.

Modulation of jaw reflexes induced by noxious stimulation to the muscle in anesthetized rats.

Previous studies have shown that jaw reflexes and activity patterns of the jaw muscles were modulated in the presence of jaw muscle pain. However, there is no study comparing the modulatory effects on the jaw reflexes induced by noxious stimulation to the jaw muscle. To clarify this, effects of the application of mustard oil (MO), an inflammatory irritant, into the temporalis (jaw-closing) muscle on (1) jaw-opening reflex evoked by tooth pulp stimulation (TP-evoked JOR) as a nociceptive reflex, (2) jaw-opening reflex evoked by inferior alveolar nerve stimulation as a non-nociceptive reflex and (3) jaw-closing reflex evoked by trigeminal mesencephalic nucleus stimulation as a proprioceptive reflex were investigated in anesthetized rats. The MO application induced suppression of all reflexes, and the effect on the TP-evoked JOR was more prominent than on the other reflexes. To elucidate the involvement of endogenous opioid system for the suppressive effect, a systemic administration of naloxone following the MO application was conducted. The MO-induced suppressive effect on the TP-evoked JOR was reversed by the naloxone administration. The results suggest that noxious stimulation to the jaw muscle modulate jaw reflexes particularly for the nociceptive jaw-opening reflex, and the modulatory effect includes both facilitatory and inhibitory aspects. The results also suggest that pain modulatory systems such as the endogenous opioid system play a crucial role in the suppression of the nociceptive transmissions related to nociceptive reflexes, and in some pathological states, defense reflexes may not be evoked properly.

Injecction of trigger points in the temporal muscles of patients with miofascial syndrome.

OBJECTIVE: The aim was to examine the effect of blocking trigger points in the temporal muscles of patients with masticatory myofascial pain syndrome, fibromyalgia and headache. METHOD: Seventy patients with one trigger point were randomly divided into 3 groups: injection with saline or anesthetic and non-injected (control). RESULTS: Pain was reduced in 87.71% patients injected with saline and 100% injected with anesthetic. Similar results were obtained for headache frequency. With regard to headache intensity, the injection groups differed from the control group, but not between themselves. CONCLUSION: Treatment with injection at trigger points decreased facial pain and frequency and intensity of headache. Considering the injected substance there was no difference.