Literature review of the adverse events associated with botulinum toxin injection for the masseter muscle hypertrophy

Masseteric Nerve Ultrasound Identification for Dynamic Facial Reanimation Purposes

BACKGROUND

The masseteric nerve is one of the main options to neurotize free muscle flaps in irreversible long-term facial paralysis. Several preoperative skin-marking techniques for the masseteric nerve have been proposed to limit the surgical dissection area, shorten the surgical time, and enable a safer dissection. However, these have shown variability among them, and cannot visualize the nerve preoperatively. The authors designed an observational study to validate a high-frequency ultrasound (HFUS) nerve identification technique.

METHODS

A systematic HFUS examination was designed and performed to visualize the masseteric nerve in 64 hemifaces of healthy volunteers. One-third were randomly selected to undergo an additional HFUS-guided needle electrostimulation to validate the HFUS image.

RESULTS

The masseteric nerve was identified by HFUS in 96.9% of hemifaces (95% CI, 0.89 to >0.99) and showed almost perfect agreement with direct needle stimulation as calculated with Cohen kappa coefficient (0.95; 95% CI, 0.85 to 1.00). The masseteric nerve was found within the masseter muscle, in between the deeper muscle bellies, at 18.3 mm (SD ±2.2) from the skin. Only in 12.9% of cases (95% CI, 0.06 to 0.24) did its course become adjacent to the mandible periosteum. Other important features, such as disposition in relation to the parotid gland, or if the nerve was covered directly by a thick intramuscular aponeurosis, could be well observed by HFUS.

CONCLUSION

HFUS enables masseteric nerve identification and can provide the surgeon with specific information on anatomical relations for each examined individual before surgery.

Exploring botulinum toxin's impact on masseter hypertrophy: a randomized, triple-blinded clinical trial

The present study aimed to assess the effectiveness and functional adverse effects of a single and multiple injections of botulinum toxin A (BoNT-A) for masseter hypertrophy (MH). Twenty-six women complaining about lower third facial enlargement due to MH, received 75 U of BoNT-A (abobotulinum toxin) in each masseter muscles. After 3 months, patients were randomly assigned to receive a second treatment session of Saline Solution: (G1; n = 11) or BoNT-A: (G2; n = 12). Muscle thickness (ultrasound), electrical activity (electromyography; EMG), masticatory performance, and subjective perception of MH were evaluated. Follow-up was performed at 1, 3 and 6 months. Muscle thickness, EMG activity, and masticatory performance were analyzed using ANOVA two-way and Sidak test as post-hoc. Masticatory performance was analyzed by the Friedman's test and Mann-Whitney test. Regarding inter-groups comparisons, there was a significant decrease in the left masseter muscle thickness in the G2 group at the 6 month follow-up (p < 0.02). For EMG, significant differences were evident at the 6 month assessment, with higher masseter activity for G1 (p < 0.05). For masticatory performance, no significant differences were observed throughout the study (p > 0.05) and a higher improvement in subjective perception of MH was observed in the 1 month follow-up for G2 (p < 0.05). In conclusion, BoNT-A is effective for MH, however multiple injections cause functional adverse effects in masseter muscle.

Functional and esthetic effects of botulinum toxin injection into the masseter muscles: evaluation of 80 patients from a dermatological perspective

BACKGROUND

Masseter muscle hypertrophy is characterized by a symmetrical or asymmetrical increase in muscle volume. Although it can be asymptomatic, it may be associated with bruxism. Therefore, patients may seek intervention for esthetic and/or functional concerns. This study aimed to establish patient characteristics, purpose of undergoing botulinum toxin injection into the masseter muscles, efficacy, and side effects of the procedure at a dermatology clinic.

METHODS

A retrospective chart review was carried out over a period of one year from January 2022 to January 2023 for the patients who underwent botulinum toxin injection into the masseter muscles. The general characteristics of patients, the purpose of botulinum toxin treatment, relief levels regarding bruxism according to the Visual Analog Scale (VAS), side effects, and complications were recorded.

RESULTS

The study group comprised 74 female and 6 male patients with a mean age of 31.20 ± 6.71 years. Eighteen (22.5%) patients were treated only for narrowing the lower face contour, 28 (35%) patients were treated only for the relief of bruxism, and 34 (42.5%) patients were treated for both indications. Fifteen (18.8%) patients experienced 16 treatment-related side effects, including two (2.5%) with smile asymmetry and two (2.5%) with paradoxical bulging.

CONCLUSIONS

Botulinum toxin injection into the masseter muscles with the intention of lower face contouring and/or relieving bruxism offers a minimally invasive, safe, and effective treatment option. Although it has a favorable safety profile, the risks of significant side effects or complications remain.

Efficacy and Safety of PrabotulinumtoxinA in Subjects With Benign Masseteric Hypertrophy: A Double-Blind, Randomized, Placebo-Controlled, Multicenter, Phase 3 Trial and Open-Label Extension Study

BACKGROUND

Despite the widespread use of botulinum toxin (BTX) injection for the treatment of masseter muscle hypertrophy (MMH), there is no standard treatment option.

OBJECTIVE

We report the efficacy and safety for BTX in MMH over a period of 48 weeks.

METHODS

In double-blinded, placebo-controlled phase 3 trials, 180 patients (randomized 1:1) received treatment with placebo (normal saline) or prabotulinumtoxinA (48 units). Masseter muscle thickness (at maximal clenching and resting positions), 3D imaging analysis, and masseter muscle hypertrophy scale grades were analyzed at each time point. After the 24-week CORE study, all patients who met the same criteria of the CORE study at week 24 ( n = 114) received only prabotulinumtoxinA, regardless of previous treatment, for an additional 24 weeks (48 weeks in total) for the open-label extension study.

RESULTS

The largest differences in mean and percent changes from baseline in masseter muscle thickness were observed at 12 weeks, and there were significant differences between the 2 groups at all time points (all p < .001). The effect was independent of the number of injections. No serious adverse event was observed.

CONCLUSION

PrabotulinumtoxinA could effectively ameliorate MMH without major complications.

Temporalis Muscle Changes Following Botulinum Toxin A Injections in Masseter Hypertrophy Patients: A Randomized Triple-Blinded Trial

BACKGROUND

This study aimed to elucidate the effects of botulinum toxin A (BoNT-A) treatment for patients diagnosed with masseter hypertrophy on the temporalis muscle, with a particular focus on assessing alterations in muscle thickness, electromyographic (EMG) activity, and the development of muscle pain.

METHODS

The present randomized triple-blinded clinical trial enrolled 26 female participants aged between 25 and 50 years complaining about masseter hypertrophy. Participants received 75U of BoNT-A (abobotulinumtoxinA) in both masseter muscles and after three months were randomized to receive a second treatment session of saline solution (S-BoNT-A) or BoNT-A (M-BoNT-A). Longitudinal assessments included temporalis muscle thickness through ultrasound, EMG activity, subjective pain, and masseter prominence severity after one, three, and six months of the first injection session. Muscle thickness, EMG, and subjective pain were analysed using two-way ANOVA with repeated measures and post hoc Sidak test, and for masseter prominence severity, Friedman and Mann-Whitney tests were used.

RESULTS

Regarding inter-group comparisons, a higher muscle thickness (p < 0.02) and a higher EMG activity (p < 0.01) were found in the M-BoNT-A group at the 6-month follow-up. For subjective pain assessments, inter-group comparisons showed a higher prevalence of painful regions in M-BoNT-A group at the 6-month follow-up (p < 0.02). No significant differences were found in masseter prominence severity at the 6 months assessment between groups.

CONCLUSION

BoNT-A treatment for masseter hypertrophy lead to structural and functional changes in the temporalis muscle, presenting higher changes after multiple injections of this treatment.

LEVEL OF EVIDENCE I

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Three-Dimensional Photography for Evaluating the Effectiveness of Botulinum Toxin Injection for Masseter Hypertrophy

BACKGROUND

Masseter hypertrophy is a common condition that causes a undesirable square face, and often treated with botulinum toxin type A (BoNTA). Subjective assessments of BoNTA effectiveness vary from physician to patient, necessitating an objective approach for evaluation. This study introduces three-dimensional photography (3DP) for the first time in clinical assessment to evaluate BoNTA treatment for masseter hypertrophy.

METHODS

Ten patients received 36U of BoNTA at three injection points on each side masseter muscle. 3DP scanner using Artec Eva® was taken at the first, third, and sixth postoperative months for objective evaluation. Patient's self-perceived prominence, patients self-rated satisfaction, and physicians provided 5-grade scores were the subjective indicators.

RESULTS

A significant decrease in left masseter volume at the sixth month (P = 0.002, P = 0.004 at rest and clenching, respectively) was observed. Patient's self-perceived prominence decreased at the first (P = 0.021) and third (P = 0.039) months. Physicians' scores significantly decreased at all postoperative months. No significant changes were noted in the right masseter volume and patients self-rated satisfaction. Patient self-rated satisfaction did not consistently correlate with objective measures, except for left masseter with clenching at the sixth month.

CONCLUSION

Three-dimensional photography accurately quantifies facial changes post-BoNTA treatment. Despite objective improvements, patient satisfaction may not align consistently. Reliable assessment tools are crucial in cosmetic surgery to manage expectations and prevent disputes.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Impact of SARS-CoV-2 Vaccination or Infection on the Safety and Efficacy of Aesthetic Injections: A Systematic Review

BACKGROUND

Aesthetic injections have become increasingly popular for maintaining a youthful appearance. However, with the rise of SARS-CoV-2, there have been concerns about potential complications. This study aims to summarize and understand the complications that occur in individuals who have received cosmetic injections after SARS-CoV-2 infection or vaccination. By doing so, we hope to provide recommendations to minimize these complications and ensure the safety of aesthetic treatments in the current COVID-19 era.

METHODS

The PRISMA guidelines, the Preferred Reporting Program for Systematic Reviews and Meta-Analyses, were used for this review. Databases including PubMed, EMBASE, Medline, Web of Science and ScienceDirect were searched. The last search time of each database was May 10, 2023. In addition, relevant references were manually searched.

RESULTS

A total of 26 studies containing 139 patients were searched. The complication with the highest percentage of reported patients was delayed inflammatory response (DIR) (n = 68; 48.92%), followed by diminished efficacy (n = 45; 32.37%) and filler reaction (n = 12; 8.63%). The remaining complications include hypersensitivity reactions, symptomatic hypercalcemia, sub-acute hypersensitive reactions, hyperalgesia, infection, fat necrosis and granulomatous reaction.

CONCLUSIONS

Cosmetic injectable procedures are generally safe but may have adverse effects, particularly during the pandemic. It is important for individuals to fully understand these risks beforehand. Clinicians should be knowledgeable about adverse event mechanisms and management to prevent issues. Industry leaders should strengthen risk management efforts to ensure safe and steady development of cosmetic injections. Overall, a comprehensive understanding, effective communication and risk management are crucial for the safe use of cosmetic injectable procedures.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors at www.springer.com/00266 .

Oculomotor and trochlear nerve neuritis following botulinum toxin injection for masseter hypertrophy - a case report with literature review

OBJECTIVE

To report a rare complication of oculomotor and trochlear nerve neuritis following botulinum toxin injection for masseter hypertrophy.

CASE PRESENTATION

A previously healthy 31-year-old man presented with a two-week history of left eye (OS) ptosis and diplopia, following botulinum toxin injection over the masseter area for masseter hypertrophy at an aesthetic centre. He had no proptosis or facial asymmetry. Visual acuity was 6/6 in the right eye (OD) and 6/9 in the OS. There was anisocoria, with pupils measuring 3 mm in the OD and 5 mm in the OS but no relative afferent pupillary defect. OS appeared hypertropic in primary gaze with impaired intorsion. Extraocular movement of the OS was restricted in all gazes, except for laevoversion; that of the OD was normal. This was associated with diplopia in all gazes except on laevoversion. Both eyes' anterior and posterior segment examinations were otherwise unremarkable. Besides the oculomotor and trochlear nerve, the other cranial nerves and neurological examinations were normal. Investigations including blood and cerebrospinal fluid, magnetic resonance imaging and angiography of the brain, were normal. Our impression was left oculomotor and trochlear nerve neuritis secondary to botulinum toxin injection. He was started on oral prednisolone 1 mg/kg daily and tapered by 5 mg per week. His condition improved gradually with no residual ptosis or anisocoria after three months. Extraocular movements normalised except for minimal residual restriction on depression.

CONCLUSION

Oculomotor and trochlear nerve neuritis can occur following botulinum toxin injection over the masseter area. Healthcare professionals should be aware of this potential complication before offering the injection.

Ultrasonographic Analysis of Trapezius Muscle for Efficient Botulinum Toxin Type A Injection

BACKGROUND

Patients nowadays seek medical reduction of the upper trapezius muscle to achieve aesthetic pleasing necklines. Botulinum toxin type A (BoNT-A), a neurotoxin that reduces the force of muscle contraction, is widely used for shoulder contouring. However, detailed metrical data are lacking to guide clinical injection.

METHODS

Forty healthy young women were enrolled. All subjects were seated for point marking and measuring of trapezius muscle (TM) anatomical data. At marked locations, the thickness of the subcutaneous tissue, the thickness of the TM, the TM's anterior border, and the depth from the skin surface to the middle of TM were measured using a real-time ultrasound scanner. In addition, photos were taken to assess the shoulder area proportion and shoulder angle.

RESULTS

The shoulder area size among participants was 90 ± 15.2 cm2, the average area proportion was 0.55 ± 0.1, and the shoulder angle was 23.12° ± 2.9°. Ultrasonography data reveal that the thickness of the subcutaneous tissue, the thickness of the TM, and the depth from the skin surface to the middle of TM all thickened from the anterior line to the posterior line (P < 0.001). The length of the TM extending forward was 1.47 ± 0.4 cm (range 0.51-1.31 cm). To better evaluate the appearance of the trapezius muscle, we constructed a grading system correlated to shoulder angle.

CONCLUSION

In this study, ultrasonography and photos were applied to assess the TM's anatomical features. Trapezius hypertrophy was described on a scale from 0 to 2 based on the shoulder angle. The findings of the present study provide a practical clinical guidance for precise and efficient BoNT-A administration.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Treatment of Facial Flaccidity and Sagging after Botulinum Toxin A Injection into the Masseter

BACKGROUND

Botulinum toxin A injection for masseter reduction is generally considered minimally invasive, safe, and effective. However, this approach may lead to facial flaccidity and sagging, especially in older patients with reduced elasticity of the skin and the soft tissue.

METHODS

The authors analyzed 27 cases of patients who presented with the above complications and treated them with botulinum toxin A injections into the platysma and the depressor anguli oris muscle. The efficacy of treatment was evaluated by both patients and physicians.

RESULTS

Ninety-six percent of patients were satisfied with the treatment outcome. One patient considered the treatment outcome unsatisfactory because of the lack of significant improvement in nasolabial folds. Physician evaluation suggests significant improvement in all patients, including the one who considered the treatment outcome unsatisfactory.

CONCLUSION

Botulinum toxin A injection into the platysma and the depressor anguli oris muscles is a safe, convenient, and effect treatment to correct the complication of facial flaccidity and sagging after masseter reduction.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Botulinum Toxin Injection for Masseteric Hypertrophy Using 6 Point Injection Technique - A Case Report. Proposal of a Clinical Technique to Quantify Prognosis

Introduction

Masseter hypertrophy presents as unilateral or bilateral swellings over the ramus and angle of the mandible. It is caused by malocclusion, clenching, TMJ disorders, etc and alters facial symmetry, leading to discomfort and negative cosmetic impact in many patients, making this a popular request for aesthetic and functional correction.

Materials and Methods

This case report involves injecting Botulinum toxin into 6 equidistant bulging points on the masseter. Standardized photography and clinical parameters were used to assess facial contour and masseter muscle thickness at baseline and successive follow ups.

Results and Discussion

Significant masseteric bulk reduction was observed in subsequent follow ups.

Conclusion

The 6-point technique was found to be an effective treatment modality for Botox injection in masseteric hypertrophy. The clinical method to quantify prognosis was easy and economical.

Combined Effects of Botulinum Toxin Injection and Oral Appliance Therapy on Lower Facial Contouring: A Randomized Controlled Trial

(1) Background: Botulinum toxin (BoNT) injection is an esthetically effective and safe treatment for contouring the lower face. This study aimed to evaluate the combined effects of BoNT and supplementary oral appliance (OA) therapy on lower facial contouring. (2) Methods: We conducted a prospective randomized controlled trial from January 2015 to June 2016 at the Yonsei University Dental Hospital. Volunteers aged 20−45 years with masseter hypertrophy were randomly assigned to one of two groups: the non-OA group and the OA group. The non-OA group received BoNT injections alone, whereas the OA group received an OA in addition to BoNT injections. Changes in the bulkiest height of the lower face were evaluated by three-dimensional laser scanning before and 4, 8, 12, and 24 weeks after injections in both groups. (3) Results: In both groups, the bulkiest height reductions decreased, with a significant interaction between group (p = 0.046) and time (p < 0.001), although the overall reduction was at a similar level at 24 weeks. (4) Conclusions: The pattern of the bulkiest height reduction of the lower face after BoNT injection differed between standalone treatment and OA therapy, implying a normalizing effect of OA on masseter muscle activity.

Guidelines for botulinum neurotoxin injection for facial contouring

SUMMARY

The hypertrophied temporalis and masseter muscles give a muscular shaped and bulky contour to the face. Botulinum neurotoxin injection methods are commonly used for facial contouring; however, adverse effects have been reported owing to a lack of delicate anatomical information. The anatomical considerations when injecting botulinum neurotoxin into the temporalis and masseter muscles have been reviewed in the present study. Current knowledge on the localization of the botulinum neurotoxin injection point with more recent anatomical dissection and modified Sihler's staining procedures was assessed. We found that for the muscles, the injection point can be more precisely demarcated. Optimal injection sites are presented for the temporalis and masseter muscles, and the injection technique has been suggested. We propose the optimal injection sites in relation to external anatomical landmarks for the frequently injected muscles of the face to facilitate the efficiency of botulinum neurotoxin injections. In addition, these guidelines would aid in more precise practice without the adverse effects of botulinum neurotoxin.

Botulinum toxin A in dentistry and orofacial surgery: an evidence-based review - part 2: cosmetic applications

Objective An evidence-based review on the role of botulinum toxin type A (BoNTA) on diverse cosmetic applications of interest to dental practitioners and allied specialities. In this context, to identify the cosmetic treatments that have an evidence-based rationale against areas requiring further research, with a view to assess the safety and efficacy of BoNTA.Data source and selection A comprehensive search was conducted using Cochrane Library of Systematic Reviews, Cochrane Central Register of Controlled Trials, and PubMed (Medline) electronic databases. Thirty-nine studies of variable quality were included. The Best Evidence Topics (BETs) Critical Appraisal Tool was used to facilitate the quality assessment of relevant studies.Data extraction Based on current level II evidence, BoNTA was safe and effective to improve facial contour, reduce volume and thickness of bilateral hypertrophic masseter. Conservative doses using a combined approach of BoNTA and hyaluronic acid was recommended as a safe and effective treatment for perioral enhancement supported by level II evidence. There was limited evidence, not higher than level III, to support BoNTA effectiveness for gummy smile associated to perioral musculature hyperactivity, while jawline sculpting targeting the platysma muscle had lower level IV evidence up to this date.Conclusion BoNTA has been widely used off-label for the investigated cosmetic orofacial conditions, with reports of 'good patient and practitioner satisfaction'. However, there is limited high-quality evidence to support the long-term safety and effectiveness of repetitive BoNTA injections. Additionally, no studies were found that provided a cost-effectiveness evaluation of BoNTA formulations against other current cosmetic interventions. Well-designed clinical trials, including long-term follow-up, would help to provide robust evidence-based recommendations for clinical practice, supporting BoNTA popularity, independently or in a combined approach.

Botox Therapy for Hypertrophy of the Masseter Muscle Causes a Compensatory Increase of Stiffness of Other Muscles of Masticatory Apparatus

Little is known about the nature of masseter muscle hypertrophy. We investigated the masseter muscle stiffness change after a single intra-masseteric session of Botox injections in people with benign bilateral masseter hypertrophy and the effect of the treatment on the stiffness of the temporalis muscle. Stiffness of the muscles was measured with shear-wave elastography at baseline and 3 weeks after Botox injections in 22 otherwise healthy people. Before the treatment, the stiffness of the masseter was lower than of the temporalis muscle (10.18 ± 1.67 kPa vs. 11.59 ± 1.54 kPa; p = 0.002). After the treatment, this difference increased (6.38 ± 1.34 vs. 13.10 ± 1.92; p < 0.0001). The drop in the stiffness of the masseter muscle was symmetrical (left side by 3.78 kPa; right side by 3.83 kPa). No differences between the left and right sides of the face in terms of muscle stiffness were observed. The study shows that Botox injections reduce stiffness of the masticatory muscles which, in turn, increases the stiffness of the temporalis muscles. Due to the knock-on effect of the change in the masseter function on the other masticatory muscles, simultaneous evaluation and treatment of the temporalis muscle may be required to ensure the desired functional and cosmetic effect.

Botulinum Toxin Type A: Adverse Events and Management

Aesthetic medicine is witnessing an increasing exploitation of all the procedures. The demand has never been higher than it is today. The number of practitioners is also increasing year by year. Consequently complications and other kinds of related troubles and procedures are also rising. Never like today is fundamental, in case of troubles, how to properly manage with the most frequent issues. In aesthetic medicine field, botulinum toxin procedures are the safest. Lot of patients are worried about botulinum toxin despite the available scientific literature. Rare short-term complications are observed. In the most of cases, nothing severe occurs if the international recommendations and the most recent guidelines are closely followed, the majority of them are injection related. This study is a review of rare or common problems that can occur and how to manage or solve the situations.

The "Visible" Muscles on Ultrasound Imaging Make Botulinum Toxin Injection More Precise: A Systematic Review

BACKGROUND

Botulinum toxin (BoNT) injection is the most commonly performed procedure in cosmetic surgery. However, blind injection is unable to take individual anatomical variations into consideration, which is the main contributing factor to complications. Ultrasound (US) imaging was introduced to reduce complications and improve effects. This article will review uses of US in aesthetic BoNT injection.

METHOD

A systematic electronic search was performed using the PubMed, MEDLINE, Web of science. Search terms were set to focus on aesthetic BoNT injection. Two independent reviewers subsequently reviewed the resultant articles based on strict inclusion and exclusion criteria. Selected manuscripts were analysed and grouped by procedure categories. Clinical cases were all performed by one plastic surgeon in our department.

RESULTS

The search finally retained 24 articles. Five procedural categories were identified, including masseter (n = 16), frontalis (n = 2), glabella complex (n = 2), trapezius (n=1), and gastrocnemius (n = 3). US imaging is practical and instructive for pre-operative assessments as in needle-type selection, injection point localization and depth setting, as well as post-operative follow-ups regarding injection feedback (for instance, the extent of muscle volume decreases). What's more, ultrasound-guided injection makes needle trajectory visualized so as for the needle to reach the target muscle in avoidance of potential damage to neurovascular bundle, gland or adjacent muscle.

CONCLUSION

Muscles, such as masseter, frontalis, glabella complex, trapezius and gastrocnemius, and their adjacent structures can be well visualized using US, and as such, US can be a useful tool for a variety of pre-operative, intra-operative and post-operative procedures.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Pivotal role of injection volume on sunken cheek prevention in masseter muscle BoNT-A injection: A cadaver study

BACKGROUND

Botulinum neurotoxin A injection is a popular noninvasive alternative for the treatment of masseter hypertrophy. This study was conducted to identify a safe injection volume to avoid sunken lateral cheek after botulinum neurotoxin A injection in the masseter muscle.

METHODS

One milliliter or 0.5 ml of indocyanine green was randomly injected into either side of the masseter muscles of 18 fresh cadaver heads. The bilateral spreads of indocyanine green within the masseter were observed by a fluorescence imager. The masseters were then dissected, and the spreading distance was measured.

RESULTS

Dye spreading showed an oval shape parallel to the long axis of the masseter muscle. The lower edges of the masseters were all stained with indocyanine green. The upward spreading exceeded the mouth corner-tragus line in 94.44% (17/18) of the masseters on the 1-ml side, and 11.11% (2/18) of the masseters on the 0.5-ml side. The spreading area and upward spreading distance on the 1-ml side (9.95 ± 0.48 cm² , 3.18 ± 0.31 cm) were significantly larger than the 0.5-ml side (7.13 ± 0.80 cm² , 2.08 ± 0.32 cm).

CONCLUSIONS

The spread of indocyanine green within the masseter occurs in direct proportion to its volume. A bolus of 1 ml easily exceeded the mouth corner-tragus line and cause sunken cheek.

Complications of Botulinum toxin A: An update review

Cosmetic surgery procedures have increased manifolds all over the world owing to the ever-increasing demand of people to look beautiful and young. Injectable treatments like botulinum toxin are becoming more popular owing to their rapid, well-defined, and lasting results for the reduction of facial fine lines, wrinkles, and facial rejuvenation. These emerging treatments are quite safe but can have certain adverse effects. In this article, we have highlighted the complications and side effects of botulinum toxin based on the anatomical location. The possible causes and precautions to prevent these complications are also discussed. The search of literature included peer-reviewed articles including clinical trials and scientific reviews. Literature was identified from electronic databases (MEDLINE/PubMed) through January 2021 and references of respective articles and only the articles published in English language were included.

Hyperhidrosis and Aesthetics

When one considers the avalanche of new indications and uses for botulinum toxins, it is truly surprising that this has all happened in such a short time. And the safety and dependability of these products are profound, when used appropriately. There is still much to be discovered about the potential of this agent when you contemplate the profound non-cosmetic benefits reported by clinicians and scientists from around the world. The mechanism of action has been studied in depth, and yet the benefits appreciated by people with chronic migraine or major depressive disorder, for instance, are unlikely to be explained by our current mechanistic understanding. Given that these toxins control acetylcholine at the motor end plates, and given that acetylcholine is central to practically every cell in the body, it will not be surprising to find that botulinum toxin researchers will be enjoying many decades of fruitful studies. The advent of the non-surgical aesthetic physician has helped push the clinical utilization of botulinum toxins well beyond its original adoption by oculoplastic surgeons in their patients with blepharospasm. We can expect that the next edition of this book to have a dozen or more new indications which will surprise us all.

Transverse facial artery: Its role in blindness after cosmetic filler and botulinum toxin injections

Masseter injections for cosmetic or pathological reasons are increasingly common, as are filler injections using dual or multiplane techniques in the lateral facial regions or for jawline contouring. The occurrence of blindness following these procedures often remains unexplained. This study aimed to determine the anatomical explanation for this debilitating complication by investigating the transverse facial artery and its relation to the masseter. For this purpose, we dissected 35 cheek specimens with latex injections and 10 specimens without latex. The external carotid artery was dissected up to its bifurcation into the maxillary and superficial temporal arteries. Results showed that the transverse facial artery arose from the superficial temporal or external carotid artery that runs between the zygomatic arch and the parotid duct. Three types of transverse facial arteries were observed: type I: a short artery that did not extend beyond the masseter muscle; type II: a transverse artery that ran to the nasolabial fold and anastomosed to the facial artery; and type III: a sizable transverse artery that substituted the hypoplastic facial artery, continued as the angular artery, and then anastomosed to the dorsal nasal artery. Knowledge of these three types of transverse facial arteries is a prerequisite to study the vascular territory. Type III provides an explanation for the occurrence of blindness after lateral face injections. We consequently define a line that runs from the tragus to the outer quarter of the upper lip as the risk area, while the safe zone is located on either side of this line.

Ultrasound dimensional changes of the anterior belly of the digastric muscle induced by orthognathic surgery and botulinum toxin A injection in Class II malocclusion

OBJECTIVES

The aim of the study is to evaluate the ultrasonographic dimensional changes of the anterior belly of the digastric muscle (ABDM), occurring after intramuscular botulinum toxin A (BTX-A) injection during orthognathic surgery, in a series of five Class II malocclusion patients.

METHODS

All the patients received 20 units of BTX-A, into both ABDM, intraoperatively. The length, width and cross-sectional area (CSA) of the ABDM were ultrasonographically measured at three different time points: T₀ (preoperatively), T₁ (postoperatively at 2 weeks after the surgical intervention), and T₂ (postoperatively at 6-9 months).

RESULTS

A statistically significant higher length of the ABDM was noted postoperatively, at T₁ and T₂ compared to T₀. The patients showed an increased length by 12.2% at 2 weeks postoperatively and continued to increase, reaching 24.6% at 6 months. A decreased width of ABDM by 6.5% at T₁ compared with T₀ was also found.

CONCLUSIONS

Postoperative ultrasound (US) follow-up measurements in patients with Class II malocclusion, orthognathic surgery and intraoperative BTX-A injection in the ABDM, showed dimensional changes of the muscle, with elongation and thinning. The muscular modifications were more pronounced at 6 months postoperatively, indicating consistency and potential benefit of using BTX-A in reducing the risk of surgical relapse. Further data on longer-term follow-up and larger number of cases are necessary.

Ultrasonographic Considerations for Safe and Efficient Botulinum Neurotoxin Injection in Masseteric Hypertrophy

There are still concerns about masseteric bulging due to a lack of knowledge about the internal architecture of the masseter muscle. Further investigations are therefore required of the most-effective botulinum neurotoxin (BoNT) injection points and strategies for managing masseteric bulging. The purpose of this study was to identify safer and more effective botulinum neurotoxin injection points and strategies by using ultrasonography to determine the structural patterns of the deep inferior tendon. We also measured the precise depths and locations of the deep inferior tendon of the masseter muscle. Thirty-two healthy volunteers participated in this study, and ultrasonography was used to scan the masseter muscle both longitudinally and transversely. Three structural patterns of the deep inferior tendon were identified: in type A, the deep inferior tendon covered the anterior two-thirds of the masseter muscle (21.8%); in type B, the deep inferior tendon covered the posterior two-thirds of the masseter muscle (9.4%); and in type C, the deep inferior tendon covered most of the inferior part of the masseter muscle (68.8%). Depending on the ultrasonography scanning site, the depth from the skin surface to the mandible in the masseteric region ranged from 15 to 25 mm. The deep inferior tendon was typically located 2 to 5 mm deep from the mandible. Ultrasonography can be used to observe the internal structure of the masseter muscle including the deep inferior tendon in individual patients. This will help to reduce the side effects of masseteric bulging when applying retrograde or dual-plane injection methods depending on the structural pattern of the deep inferior tendon.

Comparison between Conventional Blind Injections and Ultrasound-Guided Injections of Botulinum Toxin Type A into the Masseter: A Clinical Trial

The aim of the study was to propose a more efficient and safer botulinum toxin type A (BoNT-A) injection method for the masseter by comparing the conventional blind injection and a novel ultrasonography (US)-guided injection technique in a clinical trial. The 40 masseters from 20 healthy young Korean volunteers (10 males and 10 females with a mean age of 25.6 years) were included in this prospective clinical trial. The BoNT-A (24 U) was injected into the masseter of each volunteer using the conventional blind and US-guided injection techniques on the left and right sides, respectively, and analyzed by US and three-dimensional (3D) facial scanning. One case of PMB (paradoxical masseteric bulging) was observed on the side where a conventional blind injection was performed, which disappeared after the compensational injection. The reduction in the thickness of the masseter in the resting state differed significantly at 1 month after the injection between the conventional blind injection group and the US-guided injection group by 12.38 ± 7.59% and 17.98 ± 9.65%, respectively (t(19) = 3.059, p = 0.007). The reduction in the facial contour also differed significantly at 1 month after the injection between the conventional blind injection group and the US-guided injection group by 1.95 ± 0.74 mm and 2.22 ± 0.84 mm, respectively (t(19) = 2.908, p = 0.009). The results of the study showed that the US-guided injection method that considers the deep inferior tendon by visualizing the masseter can prevent the PMB that can occur during a blind injection, and is also more effective.