An evidence-based review of botulinum toxin (Botox) applications in non-cosmetic head and neck conditions

Evaluation of the quality of Internet information on masseter botox injection for bruxism

BACKGROUND

Botulinum toxin, commonly referred to as botox, is frequently used in facial aesthetics, but also has therapeutic applications in various medical and surgical conditions such as bruxism treatment.

OBJECTIVE

The aim of this research is to evaluate the information quality of only English resources available on the Internet regarding the use of botulinum toxin in the treatment of bruxism.

METHODS

The terms "Botox + Tooth Grinding" selected for this study were searched on the Internet using the Google Search Engine, and the URLs of the top 150 websites containing only English pages were recorded and examined. The websites were assessed using DISCERN tools, the Journal of the American Medical Association (JAMA) benchmark, and HONcode tools. The website readability evaluation involved utilizing the Flesch Reading Ease Score (FRES) and the Flesch-Kincaid Grade Level (FKGL).

RESULTS

A total of 130 websites met the inclusion criteria. The total mean DISCERN score (section 1 + section 2) for all websites was 39.75/75 (range: 15-67). The average FRES of all websites was 52.79, and the average FKGL score of all websites was 10.72. Internet blog websites had significantly higher DISCERN (Section 1) scores than other websites (p= 0.007). Only one website had the HON code. Internet blog websites showed better compliance with JAMA (authorship and currency) benchmarks. No statistically significant difference was determined related to FRES and FKGL scores between groups (p> 0.05).

CONCLUSIONS

There is moderate and difficult-to-read information on the Internet about masseter botox injection for bruxism. Relevant guidelines are needed to improve the quality of websites about botulinum toxin for the treatment of bruxism.

Treatment of oromandibular dystonia with botulinum toxin A improves apnea in a teenager with quadriplegic cerebral palsy: A case report

This report describes a 15-year-old female with known spastic and dystonic quadriplegic cerebral palsy (CP), Gross Motor Function Classification System IV, and obstructive sleep apnea (OSA). She experienced decreased apneic episodes after receiving onabotulinumtoxin A (BoNT-A) injections for the treatment of oromandibular dystonia (OMD). After her OSA diagnosis, she initially received injections to the bilateral masseter and temporalis muscles with no effect on the frequency of nightly apneic episodes. Subsequently, the bilateral lateral pterygoid muscles were added and she was later noted to have fewer apneic episodes overnight. This case report describes the use of BoNT-A in the muscles of mastication for management of OMD and the ensuing improvement in OSA in a teenager with CP.

Guidelines for the Use of Botulinum Toxin in Otolaryngology From the Korean Society of Laryngology, Phoniatrics and Logopedics Guideline Task Force

The Korean Society of Laryngology, Phoniatrics and Logopedics created a task force to establish clinical practice guidelines for the use of botulinum toxin (BT) in otolaryngology. We selected 10 disease categories: spasmodic dysphonia, essential vocal tremor, vocal fold granuloma, bilateral vocal fold paralysis, Frey's syndrome, sialocele, sialorrhea, cricopharyngeal dysfunction, chronic sialadenitis, and first bite syndrome. To retrieve all relevant papers, we searched the CORE databases with predefined search strategies, including Medline (PubMed), Embase, the Cochrane Library, and KoreaMed. The committee reported 13 final recommendations with detailed evidence profiles. The guidelines are primarily aimed at all clinicians applying BT to the head and neck area. In addition, the guidelines aim to promote an improved understanding of the safe and effective use of BT by policymakers and counselors, as well as in patients scheduled to receive BT injections.

Approaches to tracheoesophageal voice rehabilitation: a survey of the UK and Irish speech and language therapists' current practice and beliefs

BACKGROUND

After total laryngectomy, surgical voice restoration is used to establish communication via tracheoesophageal voice prosthesis. Once voice is established, there is a paucity of information on what speech and language therapists (SLTs) should do to improve tracheoesophageal voice quality to ensure functional communication. No existing surveys or studies investigate this specific question. There is also a disconnect between guidelines, knowledge and clinical practice, whereby clinical guidelines stipulate the requirement for SLT intervention, but do not detail what this entails in the rehabilitation context.

AIMS

(1) To advance understanding of current clinical practice beyond voice prosthesis management and care. (2) To explore what approaches are implemented in clinical practice across the UK and Republic of Ireland to rehabilitate tracheoesophageal voice. (3) To investigate the barriers and facilitators to provision of tracheoesophageal voice therapy.

METHODS & PROCEDURES

A self-administered 10-min online survey was developed using Qualtrics software and piloted before dissemination. Survey development was informed by the Behaviour Change Wheel to identify barriers, facilitators and additional factors contributing to SLTs' provision of voice therapy to tracheoesophageal speakers. The survey was disseminated via social media and professional networks. Eligibility criteria included SLTs with at least one year post-registration experience and with experience of working with laryngectomy in the past 5 years. Descriptive statistics were used to analyse closed answer questions. Open question responses were analysed using content analysis.

OUTCOMES & RESULTS

The survey received 147 responses. Participants were representative of the head and neck cancer SLT workforce. SLTs believe that tracheoesophageal voice therapy is an important aspect of laryngectomy rehabilitation; however, there was a lack of knowledge about therapy approaches and insufficient resources for implementing therapy. SLTs expressed a desire for more training, specific guidelines and a stronger evidence base to inform clinical practice. Some SLTs expressed feelings of frustration and lack of acknowledgement for the specialist skills required to undertake laryngectomy rehabilitation and tracheoesophageal work in general.

CONCLUSIONS & IMPLICATIONS

The survey identifies the need for a robust training approach and detailed clinical guidelines to promote consistent practice across the profession. The evidence base within this clinical area is emergent, hence there is a need for increased research and clinical audit to inform practice. Under-resourcing was highlighted, which should be considered in service planning to ensure that adequate staff, access to expert practitioners or time ring-fenced for therapy are available for tracheoesophageal speakers to receive the support they require.

WHAT THIS PAPER ADDS

What is already known on this subject Total laryngectomy results in life-altering changes to communication. Clinical guidelines advocate for speech and language therapy intervention; however, there is no clear information on what SLTs should do to optimize tracheoesophageal voice and the evidence base to support practice is lacking. What this study adds to existing knowledge This survey identifies what interventions SLTs provide in clinical practice to rehabilitate tracheoesophageal voice; and it explores the barriers and facilitators that influence the provision of tracheoesophageal voice therapy. What are the potential or actual clinical implications of this work? Specific training, clinical guidelines, increased research and audit are required to support clinical practice in laryngectomy rehabilitation. Service planning should address the under-resourcing of staff, expert practitioners and therapy allocated time.

Is bruxism associated with temporomandibular joint disorders? A systematic review and meta-analysis

OBJECTIVES

The aim of this review is to examine and quantify the association between bruxism and temporomandibular joint disorders in a systematic review and meta-analysis.

METHODS

Electronic searches were performed in PubMed/Medline, Embase, Cochrane, Wiley, ProQuest, Web of Science, and Scopus databases for articles published up to March 2022. Two independent reviewers assessed the quality of the studies using the Newcastle-Ottawa Scale. A random-effects model was used to estimate the pooled odds ratio (OR) and its corresponding 95% confidence interval (CI) for each study.

RESULTS

The search retrieved 1651 studies, and 20 studies were eligible for meta-analysis. The results of the study showed that there is a significant relationship between bruxism and TMD, with the presence of bruxism increasing the odds of TMD by 2.25 times (OR = 2.25, 95% CI (1.94-2.56)). Based on the type of bruxism, awake bruxism was found to increase the odds of TMD by 2.51 times (OR = 2.51, 95% CI: (2.02-2.99)), while sleep bruxism increased the odds of TMD by 2.06 times (OR = 2.06, 95% CI: (1.82-2.30)). Analysis of the results from studies that reported both types of bruxism showed that bruxism increases the odds of TMD by 2.17 times (OR = 2.17, 95% CI: (2.30-3.05)).

CONCLUSION

The available data demonstrate a positive relationship between bruxism and TMD, with the presence of bruxism increasing the likelihood of developing TMD in the future.

Developmental stuttering, physical concomitants associated with stuttering, and Tourette syndrome: A scoping review

BACKGROUND AND PURPOSE

Developmental stuttering and Tourette syndrome (TS) are common neurodevelopmental disorders. Although disfluencies may co-occur in TS, their type and frequency do not always represent pure stuttering. Conversely, core symptoms of stuttering may be accompanied by physical concomitants (PCs) that can be confused for tics. This scoping review aimed to explore the similarities and differences between stuttering and tics in terms of epidemiology, comorbidities, phenomenology, evolution, physiopathology, and treatment. We also described the nature of PCs in stuttering and disfluencies in TS.

METHODS

A literature search on Medline, Embase and PsycInfo was executed in March 2022. From 426 studies screened, 122 were included in the review (a majority being narrative reviews and case reports).

RESULTS

TS and stuttering have several epidemiological, phenomenological, comorbidity, and management similarities suggesting shared risk factors and physiopathology (involving the basal ganglia and their connections with speech and motor control cortical regions). PCs in stuttering commonly involve the face (eyelids, jaw/mouth/lip movements) and sometimes the head, trunk and limbs. PCs can be present from early stages of stuttering and vary over time and within individuals. The function of PCs is unknown. Some individuals with TS have a distinct disfluency pattern, composed of a majority of typical disfluencies (mostly between-word disfluencies), and a mix of cluttering-like behaviors, complex phonic tics (e.g. speech-blocking tics, echolalia, palilalia), and rarely, atypical disfluencies.

CONCLUSION

Future investigations are warranted to better understand the complex relationships between tics and stuttering and address the management of disfluencies in TS and PCs in stuttering.

Clinical Application of Botulinum Toxin for Hemifacial Spasm

Hemifacial spasm is typically caused by contact between the facial nerve and blood vessels. Microvascular decompression, a treatment that directly addresses this pathogenesis, is often considered the most effective treatment method. However, surgery is not immediately performed for patients at risk from the surgical treatment, or for those with an unclear diagnosis. In these instances, Botulinum toxin injection can help manage the patient's symptoms. Numerous studies corroborate the effectiveness and safety of Botulinum toxin treatment, with large-scale studies indicating symptom control lasts, on average, around 15 weeks.

Successful Treatment of Myofascial Pain Syndrome (MPS) with Surgical Cauterization of Temporalis Muscle Trigger Points: A Case Report

For patients suffering from myofascial pain syndrome (MPS) affecting muscles of mastication, traditional trigger point therapy treatment regimens can prove inconvenient, due to the short duration of pain relief after each injection and expense of repeated visits which are often not covered by insurance. We present a case of a patient treated using an alternative technique that could develop into an additional modality for treating MPS patients who are refractory to conservative treatment. This technique involves identifying and marking the patient's trigger points and surgically cauterizing each location using a Bovie electrosurgical unit. While traditional trigger point injection therapy for myofascial pain syndrome is a well-described technique with acceptable pain relief expected for a period of 8-12 weeks, this technique provided up to 24 months of adequate pain relief in a patient. While further studies are indicated before widespread adoption can be recommended, this patient's response suggests that this technique may be useful in offering longer-term pain relief compared with trigger point injection therapy.

Promising minimally invasive treatment modalities for symptomatic temporomandibular joint disc displacement with reduction: a randomized controlled clinical trial

BACKGROUND

Pain and clicking are the primary complaints in patients suffering from temporomandibular joint disc displacement with reduction (DDwR), negatively affecting the patients' quality of life, making the treatment essential. This prospective randomized controlled trial (RCT) was conducted to evaluate the effectiveness of botulinum toxin type-A (BTX-A) and low level laser therapy (LLLT) in comparison to anterior repositioning appliance (ARA) for the treatment of DDwR.

METHODS

A total of 27 patients were randomly allocated to 3 groups; ARA (control group), BTX-A, and LLLT; with 9 patients each. All patients were evaluated before and 3 months after the treatment using a visual analogue scale (VAS) and magnetic resonance imaging (MRI).

RESULTS

At 3 months follow-up, all groups showed a significant reduction in pain assessed by VAS (P = 0.007). Measured on MRI, there was a significant improvement in disc position and joint space index (JSI) in BTX-A group (P < 0.001, P = 0.011) and LLLT group (P = 0.002, P = 0.017) in comparison to the control group (P = 0.087, P = 0.066) respectively. As for time of recovery, a statistically significant difference was observed in BTX-A group (P < 0.001) and LLLT (P < 0.001) group in comparison to ARA group, which showed the most prolonged duration for reduction of DDwR symptoms.

CONCLUSION

We concluded that BTX-A and LLLT could be considered effective alternative treatment modalities to ARA regarding reducing joint pain, clicking, and improving disc position in patients with symptomatic DDwR.

TRIAL REGISTRATION

This prospective double-blinded RCT has been registered at ClinicalTrials.gov with identification number: NCT05194488, 18/1/2022.

Challenges and perspectives of tendon-derived cell therapy for tendinopathy: from bench to bedside

Tendon is composed of dense fibrous connective tissues, connecting muscle at the myotendinous junction (MTJ) to bone at the enthesis and allowing mechanical force to transmit from muscle to bone. Tendon diseases occur at different zones of the tendon, including enthesis, MTJ and midsubstance of the tendon, due to a variety of environmental and genetic factors which consequently result in different frequencies and recovery rates. Self-healing properties of tendons are limited, and cell therapeutic approaches in which injured tendon tissues are renewed by cell replenishment are highly sought after. Homologous use of individual’s tendon-derived cells, predominantly differentiated tenocytes and tendon-derived stem cells, is emerging as a treatment for tendinopathy through achieving minimal cell manipulation for clinical use. This is the first review summarizing the progress of tendon-derived cell therapy in clinical use and its challenges due to the structural complexity of tendons, heterogeneous composition of extracellular cell matrix and cells and unsuitable cell sources. Further to that, novel future perspectives to improve therapeutic effect in tendon-derived cell therapy based on current basic knowledge are discussed.

Botulinum Toxin Therapy for Oromandibular Dystonia and Other Movement Disorders in the Stomatognathic System

Various movement disorders, such as oromandibular dystonia, oral dyskinesia, bruxism, functional (psychogenic) movement disorder, and tremors, exist in the stomatognathic system. Most patients experiencing involuntary movements due to these disorders visit dentists or oral surgeons, who may be the first healthcare providers. However, differential diagnoses require neurological and dental knowledge. This study aimed to review scientific advances in botulinum toxin therapy for these conditions. The results indicated that botulinum toxin injection is effective and safe, with few side effects in most cases when properly administered by an experienced clinician. The diagnosis and treatment of movement disorders in the stomatognathic system require both neurological and dental or oral surgical knowledge and skills, and well-designed multicenter trials with a multidisciplinary team approach must be necessary to ensure accurate diagnosis and proper treatment.

European clinical guidelines for Tourette syndrome and other tic disorders-version 2.0. Part III: pharmacological treatment

In 2011, the European Society for the Study of Tourette Syndrome (ESSTS) published the first European guidelines for Tourette Syndrome (TS). We now present an update of the part on pharmacological treatment, based on a review of new literature with special attention to other evidence-based guidelines, meta-analyses, and randomized double-blinded studies. Moreover, our revision took into consideration results of a recent survey on treatment preferences conducted among ESSTS experts. The first preference should be given to psychoeducation and to behavioral approaches, as it strengthens the patients' self-regulatory control and thus his/her autonomy. Because behavioral approaches are not effective, available, or feasible in all patients, in a substantial number of patients pharmacological treatment is indicated, alone or in combination with behavioral therapy. The largest amount of evidence supports the use of dopamine blocking agents, preferably aripiprazole because of a more favorable profile of adverse events than first- and second-generation antipsychotics. Other agents that can be considered include tiapride, risperidone, and especially in case of co-existing attention deficit hyperactivity disorder (ADHD), clonidine and guanfacine. This view is supported by the results of our survey on medication preference among members of ESSTS, in which aripiprazole was indicated as the drug of first choice both in children and adults. In treatment resistant cases, treatment with agents with either a limited evidence base or risk of extrapyramidal adverse effects might be considered, including pimozide, haloperidol, topiramate, cannabis-based agents, and botulinum toxin injections. Overall, treatment of TS should be individualized, and decisions based on the patient's needs and preferences, presence of co-existing conditions, latest scientific findings as well as on the physician's preferences, experience, and local regulatory requirements.

Botulinum toxin for chronic rhinitis: A systematic review and meta-analysis

BACKGROUND

Botulinum toxin type A (BTX-A) is a potential treatment for chronic rhinitis. This study aimed to assess the effectiveness and safety of BTX-A in treating patients with chronic rhinitis.

METHODS

Systematic searches of MEDLINE, Scopus, and EMBASE databases were performed. Randomized controlled trials (RCTs) that assessed the efficacy of BTX-A in allergic rhinitis and/or nonallergic rhinitis patients, compared with either placebo or active treatment, were included. The outcomes were total nasal symptom (TNSS), disease-specific quality of life (QOL), and adverse events.

RESULTS

Nine RCTs (340 patients) met the eligibility criteria. Compared with placebo, the ≤ 12-week effects favored BTX-A injection on TNSS (standardized mean difference [SMD] -2.22, 95% confidence interval [CI] -3.27 to -1.17, p < 0.01, four RCTs). Beneficial effects > 12 weeks over placebo (MD -9.69, 95% CI -11.29 to -8.09, p < 0.01, one RCT) were demonstrated up to 24 weeks. However, the benefits were not shown on nasal congestion and individual nasal symptoms. Compared with active comparators (triamcinolone injection, ipratropium bromide, and cetirizine), there was no difference in the < 12-week effect between groups on TNSS. There was no difference between BTX-A and cetirizine on QOL (one RCT). The > 12-week effects on TNSS and individual nasal symptoms favored BTX-A over triamcinolone injection (one RCT). The risk ratio of adverse events favored BTX-A over cetirizine (one RCT).

CONCLUSIONS

BTX-A improved TNSS and QOL in patients with chronic rhinitis. These effects were demonstrated up to 24 weeks post treatment. BTX-A was safe, well tolerated, and may be considered in patients who are refractory to current standard-of-care therapies.

Intramuscular injection of Botox causes tendon atrophy by induction of senescence of tendon-derived stem cells

Background

Botulinum toxin (Botox) injection is in widespread clinical use for the treatment of muscle spasms and tendinopathy but the mechanism of action is poorly understood.

Hypothesis

We hypothesised that the reduction of patellar-tendon mechanical-loading following intra-muscular injection of Botox results in tendon atrophy that is at least in part mediated by the induction of senescence of tendon-derived stem cells (TDSCs).

Study design

Controlled laboratory study

Methods

A total of 36 mice were randomly divided into 2 groups (18 Botox-injected and 18 vehicle-only control). Mice were injected into the right vastus lateralis of quadriceps muscles either with Botox (to induce mechanical stress deprivation of the patellar tendon) or with normal saline as a control. At 2 weeks post-injection, animals were euthanized prior to tissues being harvested for either evaluation of tendon morphology or in vitro studies. TDSCs were isolated by cell-sorting prior to determination of viability, differentiation capacity or the presence of senescence markers, as well as assessing their response to mechanical loading in a bioreactor. Finally, to examine the mechanism of tendon atrophy in vitro, the PTEN/AKT-mediated cell senescence pathway was evaluated in TDSCs from both groups.

Results

Two weeks after Botox injection, patellar tendons displayed several atrophic features including tissue volume reduction, collagen fibre misalignment and increased degradation. A colony formation assay revealed a significantly reduced number of colony forming units of TDSCs in the Botox-injected group compared to controls. Multipotent differentiation capacities of TDSCs were also diminished after Botox injection. To examine if mechanically deprived TDSC are capable of forming tendon tissue, we used an isolated bioreactor system to culture tendon constructs using TDSC. These results showed that TDSCs from the Botox-treated group failed to restore tenogenic differentiation after appropriate mechanical loading. Examination of the signalling pathway revealed that injection of Botox into quadriceps muscles causes PTEN/AKT-mediated cell senescence of TDSCs.

Conclusion

Intramuscular injection of Botox interferes with tendon homeostasis by inducing tendon atrophy and senescence of TDSCs. Botox injection may have long-term adverse consequences for the treatment of tendinopathy.

Clinical relevance

Intramuscular Botox injection for tendinopathy or tendon injury could result in adverse effects in human tendons and evaluation of its long-term efficacy is warranted.

Clinical outcomes of botulinum toxin type A injections in the management of primary bruxism in adults: A systematic review

STATEMENT OF PROBLEM

Botulinum toxin has been used for various therapeutic and esthetic purposes for nearly 4 decades and has shown positive outcomes in patients with bruxism. However, the effectiveness of botulinum toxin injections as an alternative to traditional therapies in the management of primary bruxism is still unclear.

PURPOSE

The purpose of this systematic review was to analyze the clinical outcomes of the use of botulinum toxin type A injections in the management of primary bruxism in adults.

MATERIAL AND METHODS

Databases such as PubMed, Web of Science, Scopus, LILIACS, Cochrane Library, and Open Grey Literature were searched without language or date restrictions until October 6, 2019. Using Mendeley Desktop software to organize the references, 2 independent researchers selected the published clinical studies (Study type) on the improvement of symptoms (Outcome) in human adults with primary bruxism (Participants/Population) who received botulinum toxin type A injections (Intervention), placebo injections, saline injections, no injections, or other treatments (Comparator(s)/Control) for the management of bruxism.

RESULTS

A total of 601 references were initially obtained from the 6 databases. Six randomized clinical trials and 4 case series were selected and critically appraised according to the Fowkes and Fulton guidelines. Heterogeneity among the studies did not allow for a meta-analysis. All studies supported the efficacy and safety of botulinum toxin injections in reducing the symptoms of primary bruxism.

CONCLUSIONS

Botulinum toxin type A injections are effective in the treatment of the symptoms of primary bruxism in adults. Randomized clinical trials are still needed to establish a protocol for using botulinum toxin as an alternative to traditional therapies in the management of primary bruxism.

Use of botulinum toxin for movement disorders

The term movement disorders encompasses all disorders hypokinetic and hyperkinetic, which were previously known as extrapyramidal syndromes. With the definition of movement disorders and their diagnostic criteria and classifications, new studies for therapeutics could be performed. New drugs were launched, functional neurosurgery was developed, and the introduction of botulinum toxin (BoNT) for hyperkinesias was introduced. BoNT is an important therapy for dystonia, tics, myoclonus, and tremors. The aim of this review is to present the new and well-established uses of BoNT for movement disorders.

Botulinum neurotoxin a therapy efficacy and safety for oromandibular dystonia: a meta-analysis

Oromandibular dystonia (OMD) is a focal dystonia involving the mouth, jaw, and tongue. Botulinum neurotoxin (BoNT) therapy might be one form of treatment in OMD. Systematic pooling of BoNT studies in OMD remains wanting, as the derived data could provide useful information in regard to efficacy and safety issues. This meta-analysis determined the effects of botulinum neurotoxin type A (BoNT/A) on the reduction of dystonic movement and its safety among patients with OMD. A systematic search of the literature that met the following eligibility criteria were done: (1) patients treated with BoNT/A for OMD, (2) studies of high methodological quality and (3) outcome criteria specified as regard to efficacy. Risk of unresolved dystonia was computed before and after BoNT/A intervention. Random effect size (p < 0.05ɑ) and test of heterogeneity (< I2 50%) were computed as meta-analysis tool using REVMAN ver 5.3 program. Safety data, where available, were systematically reviewed. Nine studies involved 387 cases in total of OMD. The pooled risk ratio is 0.607 with a confidence interval of 0.371-0.783, a z value of 3.85, and a p value of 0.0001. Results indicate that risk of dystonic movements is lower by 39.30% in the treatment group than in the control group. A total of 105/387 patients (27.1%) experienced adverse events most commonly dysphagia. Whilst cited literatures have inherent weaknesses, results show that BoNT/A is efficacious in reducing dystonic movements of patients with OMD. Majority of studies employed electromyography (EMG) guidance in muscle targeting. Given the potential adverse event of dysphagia, one may take a cautious stand while delivering injections to target muscles. These findings are congruent with what has been published in regard to efficacy of BoNT/A in focal dystonia.

Assessing the effectiveness of botulinum toxin injections into masticatory muscles in the treatment of temporomandibular disorders

Introduction: Temporomandibular disorders (TMD) are a common and invalidating disease sometimes difficult to treat. Current international recommendations favour reversible and non-invasive treatments, including the injection of botulinum toxin (BTX) into masticatory muscles. There is no strong evidence of its effectiveness. Objective: The main goal of this study was to assess the effectiveness of BTX six months following injection, in terms of pain, mouth opening, improvement of symptoms and duration of effect. Materials and methods: A retrospective study carried out at Nantes University Hospital between 2014 and 2016. Results: Thirty-four patients were included. The mean age was 37 years (17–76) and seventy six percents were female. Eighty percent of patients reported a significant improvement, notably in cases of arthralgia, which decreased in 8/18 (44%) patients (p < 0.05). The mean duration of measured efficacy was 4.2 months. Discussion: Significant improvement in cases of arthralgia and a tendency for improvement in cases of myalgia, with a mean duration of action of 4.2 months. Although BTX injection do not guarantee complete resolution of myofascial pain, it have been shown to have beneficial effects on some symptoms have been shown. Conclusion: Botulinum toxin should be considered as an alternative treatment when other conservative methods fail to yield satisfactory results. A thorough multicentre assessment is necessary in the future to scientifically validate its use.

Chronic atypical first bite syndrome and primary squamous cell carcinoma of the parotid

BACKGROUND

First bite syndrome is a well-recognized complication of parapharyngeal space surgery. There are no reported cases of protracted first bite syndrome and subsequent diagnosis of a primary squamous cell carcinoma (SCC) of the parotid.

METHODS

We present the case of a 73-year-old man with no surgical history and 9 years of first bite syndrome who was ultimately diagnosed with a primary SCC of the parotid. Diagnostic workup, including MRI and biopsy, along with oncologic treatment, were performed.

RESULTS

Surgical treatment confirmed malignancy and also resulted in complete resolution of the first bite syndrome.

CONCLUSION

First bite syndrome without prior surgery may warrant further diagnostic workup with imaging to evaluate for salivary gland pathology. When no radiographic mass lesion is detected but the patient displays protracted symptoms unresponsive to conservative therapy, one should maintain an index of suspicion for malignancy, especially in the presence of symptom escalation.

Botulinum Neurotoxin Injection for the Treatment of Recurrent Temporomandibular Joint Dislocation with and without Neurogenic Muscular Hyperactivity

The aim of this study was to compare treatment outcomes following intramuscular injection of botulinum neurotoxin (BoNT) in patients with recurrent temporomandibular joint dislocation, with and without muscle hyperactivity due to neurological diseases. Thirty-two patients (19 women and 13 men, mean age: 62.3 years) with recurrent temporomandibular joint dislocation were divided into two groups: neurogenic (8 women and 12 men) and habitual (11 women and 1 man). The neurogenic group included patients having neurological disorders, such as Parkinson’s disease or oromandibular dystonia, that are accompanied by muscle hyperactivity. BoNT was administered via intraoral injection to the inferior head of the lateral pterygoid muscle. In total, BoNT injection was administered 102 times (mean 3.2 times/patient). The mean follow-up duration was 29.5 months. The neurogenic group was significantly (p < 0.001) younger (47.3 years) than the habitual group (84.8 years) and required significantly (p < 0.01) more injections (4.1 versus 1.7 times) to achieve a positive outcome. No significant immediate or delayed complications occurred. Thus, intramuscular injection of BoNT into the lateral pterygoid muscle is an effective and safe treatment for habitual temporomandibular joint dislocation. More injections are required in cases of neurogenic temporomandibular joint dislocation than in those of habitual dislocation without muscle hyperactivity.

Temporomandibular Joint Regenerative Medicine

The temporomandibular joint (TMJ) is an articulation formed between the temporal bone and the mandibular condyle which is commonly affected. These affections are often so painful during fundamental oral activities that patients have lower quality of life. Limitations of therapeutics for severe TMJ diseases have led to increased interest in regenerative strategies combining stem cells, implantable scaffolds and well-targeting bioactive molecules. To succeed in functional and structural regeneration of TMJ is very challenging. Innovative strategies and biomaterials are absolutely crucial because TMJ can be considered as one of the most difficult tissues to regenerate due to its limited healing capacity, its unique histological and structural properties and the necessity for long-term prevention of its ossified or fibrous adhesions. The ideal approach for TMJ regeneration is a unique scaffold functionalized with an osteochondral molecular gradient containing a single stem cell population able to undergo osteogenic and chondrogenic differentiation such as BMSCs, ADSCs or DPSCs. The key for this complex regeneration is the functionalization with active molecules such as IGF-1, TGF-β1 or bFGF. This regeneration can be optimized by nano/micro-assisted functionalization and by spatiotemporal drug delivery systems orchestrating the 3D formation of TMJ tissues.

Reproducibility of preoperative endoscopic injection of botulinum toxin into the sphincter of Oddi to prevent postoperative pancreatic fistula

Background

A postoperative pancreatic fistula (POPF) is the most common and potentially life-threatening surgical complication in pancreatic surgery. One possible pharmacological treatment could be the endoscopic injection of botulinum toxin (BTX) into the sphincter of Oddi to prevent POPF. Promising data reported a significantly reduced rate of clinically relevant POPF. We analyzed the effect of BTX injection in our patients undergoing distal pancreatectomy (DP).

Methods

A retrospective analysis of patients undergoing DP was performed. Patients with preoperative endoscopic injection of BTX into the sphincter of Oddi were included. The end points were postoperative outcomes including POPF. BTX patients were compared with a historical cohort and matched in a 1:1 ratio using a propensity score analysis.

Results

A total of 19 patients were treated with endoscopic injection of BTX before open (n=8) or laparoscopic (n=11) DP. The median age of the patients was 67 years and the mean body mass index was 25.9 kg/m². In median, the intervention was performed 1 day (range, 0–14 days) before the operation. There were no intervention-related complications. The incidence of POPF was not statistically different between the two groups: a clinically relevant POPF grade (B/C) occurred in 32% (BTX) and 42% (control; p=0.737). Likewise, there were no significant differences in postoperative drain fluid amylase levels, morbidity, and mortality.

Conclusion

The present study could not reproduce the published results of a significant lowering of grade B/C POPF. The explanations could be the timing of BTX injection before surgery and the endoscopic technique of BTX injection. However, the conflicting results after BTX injection in two high-volume centers prompt a randomized controlled multicenter trial with trained endoscopists.

Medical Aesthetics Training: Shifting to Collective Competence

With increased demands for medical aesthetics procedures and the sudden profusion of newly licensed, and unlicensed, providers who are performing these medical aesthetics procedures also comes the responsibility to shift to collective competence. Collective competence refers to what occurs among professionals in action, emphasizing the sharing of experiences, knowledge, and perceptions among those who are providing services to the medical aesthetics client. Registered nurses and medical students are not taught to perform cosmetic procedures in basic nursing or medical programs and thus require a post-entry-level education to validate their competency. The current medical aesthetics apprenticeship training approach of see one, do one, and teach one focuses on teaching technical skills and thus does not sufficiently address the ever-changing health care context and the ambiguity in practitioner role. Recent scholars highlight that when health care failed or an error has been identified, it is rarely adduced to an individual's competence but rather is more likely to be a failure of the collective team. In this article, we are advocating for a change in how medical aesthetics practitioners are trained. In particular, it advocates creating opportunities within the curricula to train practitioners as a collective body, as opposed to providing training that focuses on the individual's competence and technical skills alone.

Exocytotic fusion pores as a target for therapy

Regulated exocytosis can be split into a sequence of steps ending with the formation and the dilation of a fusion pore, a neck-like connection between the vesicle and the plasma membrane. Each of these steps is precisely controlled to achieve the optimal spatial and temporal profile of the release of signalling molecules. At the level of the fusion pore, tuning of the exocytosis can be achieved by preventing its formation, by stabilizing the unproductive narrow fusion pore, by altering the speed of fusion pore expansion and by completely closing the fusion pore. The molecular structure and dynamics of fusion pores have become a major focus of cell research, especially as a promising target for therapeutic strategies. Electrophysiological, optical and electrochemical methods have been used extensively to illuminate how cells regulate secretion at the level of a single fusion pore. Here, we describe recent advances in the structure and mechanisms of the initial fusion pore formation and the progress in therapeutic strategies with the focus on exocytosis.

Botulinum Toxin for Rhinitis

PURPOSE OF REVIEW

Rhinitis is a common clinical entity. Besides nasal obstruction, itching, and sneezing, one of the most important symptoms of rhinitis is nasal hypersecretion produced by nasal glands and exudate from the nasal vascular bed. Allergic rhinitis is an IgE-mediated inflammatory reaction of nasal mucosa after exposure to environmental allergens. Idiopathic rhinitis describes rhinitis symptoms that occur after non-allergic, noninfectious irritants. Specific allergen avoidance, topical nasal decongestants, nasal corticosteroids, immunotherapy, and sinonasal surgery are the main treatment options. Because the current treatment modalities are not enough for reducing rhinorrhea in some patients, novel treatment options are required to solve this problem.

RECENT FINDINGS

Botulinum toxin is an exotoxin generated by Clostridium botulinum. It disturbs the signal transmission at the neuromuscular and neuroglandular junction by inhibiting the acetylcholine release from the presynaptic nerve terminal. It has been widely used in neuromuscular, hypersecretory, and autonomic nerve system disorders. There have been a lot of published articles concerning the effect of this toxin on rhinitis symptoms. Based on the results of these reports, intranasal botulinum toxin A administration appears to be a safe and effective treatment method for decreasing rhinitis symptoms in rhinitis patients with a long-lasting effect. Botulinum toxin type A will be a good treatment option for the chronic rhinitis patients who are resistant to other treatment methods.

Hoarseness-causes and treatments

BACKGROUND

Hoarseness (dysphonia) is the reason for about 1% of all consultations in primary care. It has many causes, ranging from self-limited laryngitis to malignant tumors of the vocal cords.

METHODS

This review is based on literature retrieved by a selective search in PubMed employing the terms "hoarseness," "hoarse voice," and "dysphonia," on the relevant guideline of the American Academy of Otolaryngology -Head and Neck Surgery, and on Cochrane reviews.

RESULTS

Hoarseness can be caused by acute (42.1%) and chronic laryngitis (9.7%), functional vocal disturbances (30%), and benign (10.7-31%) and malignant tumors (2.2-3%), as well as by neurogenic disturbances such as vocal cord paresis (2.8-8%), physiologic aging of the voice (2%), and psychogenic factors (2-2.2 %). Hoarseness is very rarely a manifestation of internal medical illness. The treatment of hoarseness has been studied in only a few randomized controlled trials, all of which were on a small scale. Voice therapy is often successful in the treatment of functional and organic vocal disturbances (level 1a evidence). Surgery on the vocal cords is indicated to treat tumors and inadequate vocal cord closure. The only entity causing hoarseness that can be treated pharmacologically is chronic laryngitis associated with gastro-esophageal reflux, which responds to treatment of the reflux disorder. The empirical treatment of hoarseness with antibiotics or corticosteroids is not recommended.

CONCLUSION

Voice therapy, vocal cord surgery, and drug therapy for appropriate groups of patients with hoarseness are well documented as effective by the available evidence. In patients with risk factors, especially smokers, hoarseness should be immediately evaluated by laryngos - copy.

Applications of botulinum toxin in dentistry: A comprehensive review

The horizons of treatment options in dentistry are broadening rapidly. In this scenario, applications of unconventional treatment options like use of botulinum toxin (BT) are gaining momentum. The use of BT has been popularly accepted in esthetic procedures like management of facial wrinkles; however, it has been documented to be successful in a variety of conditions. Of particular interest to this paper are applications of BT in the maxillofacial region, concerned to dentistry. BT offers a transient, reversible, relatively safe treatment option to many conditions of interest to a dental practitioner. Dental surgeons by their virtue of being extensively aware of the anatomy of faciomaxillary region are a potential pool of operators who can use BT in their armamentarium with minor skill enhancement and thus widen the perspective of alternative, minimally invasive options to refractory conditions or invasive protocols.

The efficiency of botulinum toxin type A for the treatment of masseter muscle pain in patients with temporomandibular joint dysfunction and tension-type headache

BACKGROUND

Temporomandibular joint dysfunction are often accompanied by symptoms of headache such as tension-type headache which is the most frequent spontaneous primary headache. Masseter muscle pain is commonly reported in this group. The purpose of the study was to assess the efficiency of intramuscular botulinum toxin type A injections for treating masseter muscle pain in patients with temporomandibular joint dysfunction and tension-type headache.

METHODS

This prospective outcome study consisted of 42 subjects of both genders aged 19-48 years diagnosed with masseter muscle pain related to temporomandibular joint dysfunction and tension-type headache. The subjects were treated by the intramuscular injection of 21 U (mice units) of botulinum toxin type A (Botox, Allergan) in the area of the greatest cross-section surface of both masseter bellies. Pain intensity was evaluated using visual analogue scale (VAS) and verbal numerical rating scale (VNRS) 1 week before the treatment and 24 weeks after the treatment. The obtained data were analyzed using the Wilcoxon matched pairs test (p ≤ 0,005).

RESULTS

The results of this study showed a decrease in the number of referred pain episodes including a decrease in pain in the temporal region bilaterally, a reduction of analgesic drugs intake as well as a decrease in reported values of VAS and VNRS after injections (p = 0,000).

CONCLUSIONS

The intramuscular botulinum toxin type A injections have been an efficient method of treatment for masseter muscle pain in patients with temporomandibular joint dysfunction and tension-type headache.

Recent Advances in Understanding and Managing Tourette Syndrome

Tourette syndrome (TS) is a neurologic and behavioral disorder consisting of motor and phonic tics with onset in childhood or adolescence. The severity of tics can range from barely perceptible to severely impairing due to social embarrassment, discomfort, self-injury, and interference with daily functioning and school or work performance. In addition to tics, most patients with TS have a variety of behavioral comorbidities, including attention deficit hyperactivity disorder and obsessive-compulsive disorder. Studies evaluating the pathophysiology of tics have pointed towards dysfunction of the cortico-striato-thalamo-cortical circuit, but the mechanism of this hyperkinetic movement disorder is not well understood. Treatment of TS is multidisciplinary, typically involving behavioral therapy, oral medications, and botulinum toxin injections. Deep brain stimulation may be considered for “malignant” TS that is refractory to conventional therapy. In this review, we will highlight recent developments in the understanding and management strategies of TS.

Therapeutic Developments for Tics and Myoclonus

Tics and myoclonus are phenomenologically similar given that both are jerk-like movements, but, in contrast to myoclonus, tics are often preceded by premonitory sensations and are typically associated with a variety of behavioral comorbidities, including attention deficit and obsessive-compulsive disorder. There are many other clinical features that help differentiate these two hyperkinetic disorders. Whereas behavioral and antidopaminergic therapies are most effective in the management of tics, clonazepam, other anticonvulsants, and serotonergic drugs are often used to control myoclonic movements. Botulinum toxin may also be helpful in focal tics and in segmental forms of myoclonus. DBS plays an increasingly important role in the treatment of these disorders, particularly when they are generalized and are disabling despite optimal medical therapy.

Botulinum toxin in masticatory muscles of the adult rat induces bone loss at the condyle and alveolar regions of the mandible associated with a bone proliferation at a muscle enthesis

In man, botulinum toxin type A (BTX) is injected in masticatory muscles for several indications such as trismus, bruxism, or masseter hypertrophy. Bone changes in the mandible following BTX injections in adult animal have therefore became a subject of interest. The aim of this study was to analyze condylar and alveolar bone changes following BTX unilateral injections in masseter and temporal muscles in adult rats. Mature male rats (n = 15) were randomized into 2 groups: control (CTRL; n = 6) and BTX group (n= 9). Rats of the BTX group received a single injection of BTX into right masseter and temporal muscles. Rats of the CTRL group were similarly injected with saline solution. Rats were sacrificed 4 weeks after injections. Masticatory muscles examination and microcomputed tomography (microCT) were performed. A significant difference of weight was found between the 2 groups at weeks 2, 3 and 4 (p < 0.05). Atrophy of the right masseter and temporal muscles was observed in all BTX rats. MicroCT analysis showed significant bone loss in the right alveolar and condylar areas in BTX rats. Decrease in bone volume reached -20% for right alveolar bone and -35% for right condylar bone. A hypertrophic bone metaplasia at the digastric muscle enthesis was found on every right hemimandible in the BTX group and none in the CTRL group. BTX injection in masticatory muscles leads to a significant and major mandible bone loss. These alterations can represent a risk factor for fractures in human. The occurrence of a hypertrophic bone metaplasia at the Mus Digastricus enthesis may constitute an etiological factor for tori.

Bruxism: Conceptual discussion and review

Bruxism is commonly considered a detrimental motor activity, potentially causing overload of the stomatognathic structures. The etiology of bruxism is unclear, but the condition has been associated with stress, occlusal disorders, allergies and sleep positioning. Due to its nonspecific pathology, bruxism may be difficult to diagnose. Unfortunately, very little data exists on the subject of a cause-and-effect relationship of bruxism to the point that expert opinions and cautionary approaches are still considered the best available sources for suggesting good practice indicators. The present paper reviewed current concepts on bruxism, etiology, diagnosis and management, underlining its effects on dental structures in an attempt to provide clinically useful suggestions based on scientifically sound data.

An Animal Model for Inducing Deviation of the Mandible

PURPOSE

Altering the occlusal surface is still a common choice for inducing a deviated mandible in an animal model. Botulinum neurotoxin type A (BoTx/A) can block the action potential transmission in neuromuscular junctions by inhibiting acetylcholine release without damaging the nerves and muscle structures. Our present study was aimed at developing an easy-to-reproduce animal model of asymmetric mandibles in which injection of BoTx/A was applied.

MATERIALS AND METHODS

A total of 96 healthy 4-week-old male Sprague-Dawley rats were divided into 2 groups: an experimental group (n = 48) with BoTx/A injection and a control group (n = 48) with sterile saline injection at 4 sites of the right masseter muscle. Twelve rats from each group were humanely euthanized at weeks 1, 2, 3, and 4 for morphometric analysis using the micro-computed tomography (CT) findings.

RESULTS

The micro-CT scans revealed facial asymmetry in the experimental group, with no facial asymmetry in the control group after injection. Significant differences were found between the experimental and control groups regarding the indexes containing the mandibular length (length from condyle to menton, length from coronoid to menton, and length of mandibular corpus from gonion to menton) and ramus height (posterior border and middle region near coronoid, and height of anterior mandible at vertical distance from menton).

CONCLUSION

Our data have indicated that this deviated mandible animal model induced by injection of BoTx/A is highly reproducible and might be proved suitable for future studies of the asymmetric mandible.

Effects of a botulinum toxin type A injection on the masseter muscle: An animal model study

BACKGROUND

The aim of this study was to investigate the effect of a botulinum toxin type A (BTX-A) injection in the masseter muscle using electromyography (EMG) in an animal model.

METHODS

Ten male adult (>3 months of age) New Zealand white rabbits were used. Muscle activity was continuously recorded from 8 hours before to 8 hours after BTX-A injection. The rabbits received unilateral BTX-A injections of either 5 units (group 1, n = 5) or 20 units (group 2, n = 5).

RESULTS

The masseter muscle activity of the rabbits was significantly reduced immediately after BTX-A injection (P < 0.05 for both groups). When the results from group 1 were compared with those from group 2, only the peak voltage was significantly decreased in group 2 (P = 0.013).

CONCLUSION

Masseter muscle activity measured by EMG was immediately decreased after a BTX-A injection.

Botulinum toxin A for children with salivary control problems

OBJECTIVE

The aim of this study was to review the response of children who have received botulinum toxin A (BtA) injections for saliva control in our institution.

METHODS

Retrospective case series of children attending a saliva control clinic in a paediatric tertiary referral hospital. Children were identified from the saliva control database, which has been in place since its creation in 2006. Prior to receiving BtA all the children in the study had previously undertaken a 3-month trial of pharmacological therapy, with no effect. All BtA injections were performed freehand to the parotid and submandibular glands. The background diagnosis, comorbidities for the child, age at presentation, dose of BtA, the response, and any complications were recorded.

RESULTS

97 children were identified and 175 BtA doses were given (median per child: 1, mean: 1.9). 59 (61%) were male. The age range was between 2 months and 18 years (mean 8.6 years, median 8.8 years). The dose injected varied between 0.52 units/kg and 21.28 unit/kg (mean 5 units/kg, median 4.2 units/kg). These were performed using local anaesthetic on 131 (75%) occasions. The remainder were performed under general anaesthetic. Responses to BtA were classed as effective 109 (62%), partially effective 14 (8%) or not effective 50 (29%). The response duration was between 0.25 and 18 months (mean 4 months). Complications were seen following 22 injections (10.9%). Data modelled using binary logistic regression found that male gender and children with cerebral palsy are statistically predicted to have a better response to BtA.

CONCLUSION

Botulinum A injected under local anaesthetic is a safe, effective treatment for children with sialorrhoea. Ultrasound guidance is not necessary as long as anatomical landmarks are used for placement. The main adverse effect that can result is dysphagia, which is of concern in children that can swallow independently prior to injection. Male sex and cerebral palsy are statistically independent positive predictive factors for successful outcome of BtA injections for sialorrhoea, however this does not preclude other children from receiving or benefitting from it. Children that respond well to BtA initially, are likely to respond well in the future.

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.

Periodic botulinum toxin injections for paradoxical vocal fold motion in a child with cerebral palsy: a case study

We describe an unusual case of paradoxical vocal fold motion in a child with cerebral palsy. Clinically, the child presented with mild stridor, which worsened over months, eventually requiring emergency intubation. After an unsuccessful trial of medical management, microlaryngoscopy revealed abnormal adduction of the vocal folds during inspiration. This was successfully treated with periodic type A botulinum toxin injections to the vocal folds, sparing the child from tracheostomy.

Botulinum toxin-type A: could it be an effective treatment option in intractable trigeminal neuralgia?

BACKGROUND

Botulinum toxin type A (BTX-A) has been reported to have analgesic effects independent of its action on muscle tone, mostly by acting on neurogenic inflammatory mediators and controlling the neurotransmitter release of sensory and autonomic nerve terminals that are involved in many chronic painful conditions as chronic intractable trigeminal neuralgia (TN).The aim of our work was evaluating the efficacy, safety, and tolerability of BTX-A for the treatment of intractable idiopathic TN.

METHODS

This was a randomized, single-blinded, placebo-control study carried out on 20 Egyptian patients with intractable TN. Patients received a one-time subcutaneous administration of BTX-A using "follow the pain" method. The primary efficacy measure was reduction in pain severity on the 10-cm VAS score as well as in paroxysms frequency from the baseline to week 12 (endpoint last observation carried forward [LOCF]). Secondary efficacy measures included QoL assessment and number of acute medications received from baseline to the endpoint.

RESULTS

Pain reduction at the 12-week endpoint was significant in BTX-A group (p<0.0001); VAS scores at endpoint LOCF relative to baseline for BTX-A group showed a decrease of 6.5 compared with a decrease of 0.3 for placebo, also there was a significant decrease in the number of acute medications and an increase in QoL functioning scale.

CONCLUSION

These results indicate that BTX-A has a direct analgesic effect in patients with TN and can represent a therapeutic option for intractable cases.

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.