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

Ultrasonographic assessment of the lateral pterygoid muscle for BoNT-A injection

The upper head of the lateral pterygoid muscle (LPM) is known to insert into the capsule of the temporomandibular joint and articular disc, and therefore its relationship with temporomandibular disorders (TMD) has been consistently suggested. The aim of the study was to determine the anatomical features of the LPM using ultrasonographic (US) imaging. Around 120 hemifaces from 60 healthy Korean volunteers were included in this study. US images were taken with the subject's mouth 2 cm open. The transducer was placed at a position where the infratemporal fossa could be observed through the mandibular notch, and its position was recorded. The locations of the coronoid process (CorP), lateral margin of the condylar process (ConP), and midpoint of CorP and ConP (MP) were measured with reference to the ala-tragus line. The thicknesses of the skin and subcutaneous tissue, the masseter muscle, the temporalis muscle, and the depth of the LPM were measured at the MP. The masseter muscle, temporalis muscle, and LPM were observed in all cases and located in order from superficial to deep. The MP was located 39.6 ± 3.3 mm anterior and 7.8 ± 1.6 mm inferior to the tragus. The thicknesses of the skin and subcutaneous tissue, the masseter muscle, the temporalis muscle, and the depth of the LPM at the MP were 9.7 ± 1.0, 10.3 ± 1.3, 10.9 ± 1.6, and 30.9 ± 1.9 mm, respectively. The information reported in this study may be useful for determining the location of the LPM and adjacent anatomical structures in TMD patients and provide accurate and safe injection guidelines.

An Ultrasonographic Analysis of the Deep Inferior Tendon in the Masseter Muscle: Implications for Botulinum Toxin Injections

(1) Background: With the increasing aesthetic pursuit of facial features, the clinical use of Botulinum Toxin Type A (BoNT-A) injections for masseter hypertrophy has been on the rise. However, due to variations in masseter muscle structure and differences in clinicians' injection techniques, blind injections may lack precision, potentially compromising treatment accuracy and increasing the risk of complications. (2) Objectives: The study aims to use ultrasonography to detail the deep inferior tendon (DIT) within the masseter muscle in a young Chinese cohort, refine its classification, analyze muscle belly thickness and variations across groups, and propose a customized ultrasound-guided BoNT-A injection protocol. (3) Methods: Ultrasound imaging was used to observe the bilateral masseter muscles at rest and during clenching. The features of the DIT were classified from these images, and the thickness of the masseter's distinct bellies associated with the DIT types was measured in both states. (4) Results: The study cohort included 103 participants (27 male, 76 female), with 30 muscles in the normal masseter group and 176 muscles in the hypertrophy group. The DIT was categorized as Type A, B (subtypes B1, B2), and C. The distribution of these types was consistent across normal, hypertrophic, and gender groups, all following the same trend (B > A > C). In hypertrophy, Type B1 showed uniform thickness across masseter bellies, B2 presented with a thinner intermediate belly, and Type C had mainly superficial muscle enlargement. Changes in muscle thickness during clenching were noted but not statistically significant among different bellies. (5) Conclusions: The study evidences individual variation in the DIT, highlighting the importance of precise DIT classification for effective BoNT-A injections. A tailored ultrasound-guided BoNT-A injection strategy based on this classification may enhance safety and efficacy of the therapy.

A prospective and randomized study comparing ultrasound-guided real time injection to conventional blind injection of botulinum neurotoxin for glabellar wrinkles

BACKGROUND

Botulinum neurotoxin injections are the most frequently performed cosmetic procedures, but conventional blind injection for glabellar wrinkles remains to have some limitations.

AIMS

We intend to directly inject botulinum neurotoxin into the glabella complex guided by real time ultrasound. We aim to propose a more efficient and safer botulinum neurotoxin injection strategy for glabellar wrinkles.

METHODS

A total of 40 subjects with moderate to severe glabellar lines were enrolled in this study to receive botulinum neurotoxin injection, either through ultrasound-guided real time injection or conventional blind injection. Facial Wrinkle Scale (ranging from 0 = none to 3 = severe) and inter-brow distance (from 3D scanned face images) were used to evaluate the glabellar wrinkles improvement. Paired t test and two-sample t test were performed to analyze the within-group and between-group differences.

RESULTS

The wrinkle score reduction was significant (p < 0.0001) immediately after the injection in ultrasound-guided injection group, but not in blind injection group (p = 0.163). Ultrasound-guided injection also showed a higher performance of wrinkle score reduction and more effective inter-brow distance increase over blind injection at Day 0 (p < 0.0001), Day 1 (p < 0.0001), Day 21 (p < 0.01) and Day 35 (p < 0.01) after initial treatment.

CONCLUSIONS

The results of the study confirmed that botulinum neurotoxin injection for glabellar wrinkles under ultrasound guidance achieves quicker onset of action and better final outcomes compared to conventional blind injection.

Ultrasound-Guided Injections for Treatment of Facial Paralysis Sequelae: A Randomized Study on Body Donors

BACKGROUND

Botulinum toxin injection is the accepted standard treatment for synkinesis and gustatory hyperlacrimation in patients with facial paralysis. However, poor injection accuracy can result in inconsistent treatment outcomes, variable treatment durations, and complications. Ultrasound guidance should increase injection accuracy in the facial region; however, this has not been proven.

METHODS

Twenty-six hemifaces of nonembalmed cadavers were studied in a randomized split-face manner. Ink was injected with ultrasound or landmark guidance into the lacrimal gland and three common synkinetic muscles: the orbicularis oculi, depressor anguli oris, and mentalis. Injection accuracy was evaluated using several measures.

RESULTS

Using ultrasound guidance, most ink (>50%) was found inside the correct target in 88% of cases, compared with 50% using landmark guidance ( P < 0.001). This was most pronounced in the lacrimal gland (62% versus 8%), depressor anguli oris (100% versus 46%), and mentalis (100% versus 54%) ( P < 0.05). All ink was found inside the correct target (no ink outside) in 65% using ultrasound guidance versus 29% without ( P < 0.001). Injection accuracy (any ink in target) was 100% when using ultrasound guidance versus 83% without ( P < 0.01). Twenty-three percent of the landmark-guided depressor anguli oris injections stained the facial artery ( P = 0.22).

CONCLUSIONS

Ultrasound guidance significantly increased injection accuracy and reduced the amount of ink lost in the surrounding tissue compared with landmark guidance. Clinical trials are needed to explore the effects of ultrasound guidance on treatment outcome, duration, and complications in patients with facial paralysis.

Do repetitive botulinum neurotoxin injections induce muscle fibrosis? Sonographic observation of the masseter muscle

OBJECTIVE

In the esthetic field, the masseter muscle is commonly targeted by botulinum neurotoxin for facial contouring. However, multiple botulinum neurotoxin injections have been reported to cause muscle fibrosis. Ultrasonography can be useful for clinical consideration in such cases.

MATERIALS AND METHODS

This study presents nine cases of masseteric fibrosis caused by repeated botulinum neurotoxin injections with ultrasonographic analysis of full and partial masseteric fibrosis.

RESULTS

Repetitive botulinum neurotoxin injections resulted in reduced masseter muscle volume, which frequently appeared hyperechoic on ultrasonography. The hyperechoic region was mostly located in the deep and posterior portions; however, in some cases, it was observed throughout the muscle, including the superficial, deep, or both areas.

CONCLUSION

The fibrotic masseter muscles appear hyperechoic, and ultrasonography is necessary to analyze the degree and location of fibrosis. Predictions can be made for cases in which botulinum neurotoxin injections may have less of an effect after ultrasonography. Because muscle fibrosis can be localized, it is necessary to confirm the degree and location of fibrosis before determining the effective area of injection. In clinical practice, muscle fibrosis may be visible in a specific area where blind injections are administered.

Analysis of Sexual Dimorphic Features of the Jawline and Chin in White Celebrity Faces

BACKGROUND

The jawline greatly influences facial shape and contributes to facial dimorphism. Analysis of lower facial shape and sexual dimorphic differences in contemporary attractive white faces can advance the goals of lower facial aesthetics and facial gender-affirming surgery (FGAS).

METHODS

Full-face, front-view photos of 47 white female and 21 white male celebrities were included from a list generated using GQ magazine's Highest Paid Models issue, People Magazine's Beautiful issue (1991-2022), and celebrities featured on lifestyle websites. Facial landmarks were detected through a facial analysis program using Vision framework and MATLAB. After converting pixel distances to absolute distances, lower face measurements were compared between males and females.

RESULTS

The mean lower facial height was 6.08 cm in females and 7.00 cm in males (P value<0.001). The mean bigonial width was 11.21 cm in females and 12.30 cm in males (P value<0.001). The ratio of facial height to lower facial height was 2.98 in females and 2.76 in males (P value<0.001), signifying that symmetry in facial thirds is more prevalent in attractive female faces, while a longer lower face is more common in attractive male faces. The greatest differences in female and male facial contours were at gonial angles and chin.

CONCLUSIONS

Analysis of contemporary white celebrity faces demonstrated significantly wider and longer lower facial measurements in males. The overall contour of the female lower face was more tapered at the gonial angles and chin compared to males. These results are important when planning lower facial rejuvenation or FGAS, as lower face size and proportions influence perceived gender and attractiveness.

Neurectomy of the Masseteric Nerve Using an Extra-Oral Approach to Treat Masseter Hypertrophy: Case Report and Literature Review

Masticatory muscle hypertrophy is a benign clinical anomaly which leads to facial asymmetry or a squared face appearance. We report a case of masticatory muscle hypertrophy, particularly on the right side, that was successfully treated by neurectomy of the right masseteric nerve through an extra-oral approach. Clinical examination showed significant aesthetic improvement of the facial symmetry with complete paralysis and atrophy of the right masseter muscle. The impaired postoperative function of the frontal branch of the right facial nerve was fully restored 10 weeks postoperatively. The patient no longer experiences headaches or discomfort with eating or sleeping on her right side.

The Deep Temporal Arteries: Anatomical Study with Application to Augmentations Procedures of the Temple

The aim of this study was to determine the anatomical features of the deep temporal arteries (DTAs) and thereby provide clinical information for the temple augmentation procedure. Forty-two adult hemifaces from 15 Korean and 6 Thai cadavers (12 males, 9 females; mean age at death, 79.6 years) with no history of trauma or surgical procedure on the temple area were used for anatomical study. A detailed dissection was performed to identify the locations of the anterior and posterior deep temporal arteries (ADTA and PDTA) with reference to the vertical plane passing through the zygomatic tubercle. Fifty-eight healthy Korean participants (31 males and 27 females; mean age, 24.7 years) were included in the ultrasonographic study. The distance from the bone to the DTAs was measured at the level of the zygomatic tubercle (H_Zt ) and the eyebrow (H_Eb ). The DTAs were not found within 7.2-12.6 mm posterior to the zygomatic tubercle; instead, the locations varied widely at the H_Eb . The distances between the bone and the ADTA were 1.7 ± 1.2 mm (mean ± SD) and 1.3 ± 0.8 mm, and those between the bone and the PDTA were 2.1 ± 1.2 mm and 2.0 ± 1.4 mm at H_Zt and H_Eb , respectively. Our findings indicate that at H_Zt , the area 1 cm posterior to the zygomatic tubercle may be a safe area for deep temple augmentation procedures. However, because the distribution patterns of the DTAs at H_Eb and depth of the DTAs are variable, additional care is required to minimize the risks of the procedure.

A Comprehensive Ultrasound Evaluation Approach of Lower Facial Structure Before Masseter Muscle Botulinum Toxin Injection

BACKGROUND

Masseter reduction by botulinum neurotoxin A (BoNT-A) injection is a popular procedure in East Asia. Inappropriate injection can result in various complications.

OBJECTIVES

The aim of this study was to develop an approach for comprehensively evaluating the lower facial structure based on the shape of the mandible angle, the thickness of the masseter, and the thickness of subcutaneous fat.

METHODS

Clinical profiles and standard ultrasound images were collected from patients seeking masseter BoNT-A injections. Lower facial structures were evaluated based on 3 aspects: mandible, masseter, and subcutaneous fat and skin. The mandibular angle was classified as extroverted, straight, or introverted. The starting point of the middle part of the masseter was recorded. The thickness of the deep inferior tendon, the superficial and deep belly of the superficial part of the masseter, and their contractility were measured. Overall thickness and the thickness of subcutaneous fat and skin were also measured.

RESULTS

Eighty-four masseters from 42 patients were included. Straight mandibular angles were the most common type of angle (48.81%), followed by introverted (26.19%) and extroverted angles (25.00%). The middle part of the masseter starts from 2.33 [0.36] cm (mean [standard deviation]) above the mandible edge, which is above the usual injection points. The superficial belly was thicker than the deep belly in both static and clenching states (P = .048, P = .001) and had greater contractility. The average overall thickness was 1.87 [0.29] cm.

CONCLUSIONS

Comprehensive evaluation of the lower facial contour and structure based on ultrasound examination could be a reliable and replicable assessment approach.

LEVEL OF EVIDENCE: 4

Positional deformation of the parotid gland: application to minimally invasive procedures

Anatomical studies of the parotid gland are important for mid- and lower face filler, botulinum toxin, and thread lifting procedures. The purpose of this study was to observe the topographic anatomy of the parotid gland using cadaveric dissections. The superficial lobe of the parotid gland was studied in 30 hemisected heads. Reference lines were made on the lateral aspect of the face. A reference line (the line connecting the mandibular angle to the upper margin of the zygomatic arch, along the posterior border of the ramus) was divided into four sections (P1, P2, P3, and P4). The superior, inferior, anterior, and posterior borders of the parotid gland were measured using the reference lines and sections. Using these measurements, we categorized the superficial lobe of the parotid gland into two types: type Ia, pistol-shaped; Ib, pistol-shaped with an accessory lobe; and type II, oval-shaped. The superior border of the parotid gland started just below the inferior margin of the zygomatic arch. The parotid gland covered the posterior part of the masseter muscle near P1 and P2, but at P3 and below P3, the tail of the parotid gland was located posterior to the ramus and covered the anterior part of the sternocleidomastoid muscle. The topographic anatomy of the parotid gland serves as a reliable reference for esthetic procedures in the lower face and neck region. This article is protected by copyright. All rights reserved.

Ultrasonographic Analyses of Crow's Feet and Novel Guideline for Botulinum Toxin Injection

BACKGROUND

Crow's feet are bilateral orbital wrinkles formed by the orbital portion of the orbicularis oculi muscle, which is the target muscle for botulinum neurotoxin (BoNT) injection.

OBJECTIVES

This study's aim was to demonstrate a novel BoNT injection guideline by assessing muscle width, thickness, and dynamic features using ultrasonography.

METHODS

Twenty healthy Korean volunteers (10 men, 10 women; mean age, 25.6) participated. The width, thickness, and dynamic movement of the orbicularis oculi muscle were measured using ultrasonography. Two volunteers were selected to receive BoNT injections. Injections were administered using a novel method with two curved reference lines passing a point 15 mm lateral to the lateral canthus (conventional injection) and a point 5 mm lateral to the lateral margin of the frontal process of zygomatic bone (additional injection).

RESULT

At the lateral canthus level, the distance between the lateral margin of the frontal process and the most lateral margin of the orbicularis oculi muscle was 12.5±1.3 mm. The thickness of the orbicularis oculi muscle at the midpoint of the frontal process, the lateral marginal of the frontal process, and 5 mm lateral to the lateral marginal of the frontal process was 0.7±0.3 mm, 1.1±0.3 mm, and 1.2±0.3 mm, respectively. The crow's feet of the two volunteers began to disappear from day 3 and completely disappeared on day 7 after the injection.

CONCLUSION

The novel injection technique based on the ultrasonographic anatomy resulted in improvements in the appearance of crow's feet.

Efficacy of botulinum toxin in masseter muscle hypertrophy for lower face contouring

BACKGROUND

Masseter muscle hypertrophy (MMH) usually presents with cosmetic concerns as it may lead to widening of the lower face. Apart from the traditional surgical approaches, botulinum toxin type A (BTA) injection is a non-invasive treatment option available. There are no standard guidelines for this procedure.

OBJECTIVES

To study the efficacy of botulinumtoxin A in MMH for lower face contouring.

METHODOLOGY

The Cochrane Library, PubMed/MEDLINE, Google-scholar, Science-Direct database, and ResearchGate from inception until September 2021 were searched using the keywords "botulinumtoxin type A," "masseter muscle hypertrophy," "lower face contouring," and "masseter botox." All available retrospective and prospective studies, case-series, case-reports, and expert reviews were included with an emphasis on efficacy of BTA in MMH and units injected into the muscle, points of placement, adverse events, and the duration of its effect. Reference lists of the resultant articles, as well as relevant reviews, were also searched.

RESULT

40 articles were shortlisted for the review, of which 14 studies with sample-size ≥10 in accordance with the study requirements were summarized in a tabular form for analysis and easy comparison and reference.

CONCLUSION

BTA injection is a non-invasive, safe, and effective treatment for MMH. The optimum number of BTA units could not be ascertained due to wide variability in the studies as well as ethnicity of patients and extent or some measurement of MMH. The points of placement of injection should be well within the boundaries of the masseter muscle. The maximum effect of BTA after a single injection session is usually seen in ~3 months, and the duration may last for 6-12 months. Multiple injection sessions may be required to maintain a long-term effect. Injection technique and total number of injection units of neuromodulator must be individualized for each patient.

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 .

Anatomical Injection Guidelines for Glabellar Frown Lines Based on Ultrasonographic Evaluation

When botulinum neurotoxin (BoNT) is injected to treat glabellar frown lines, the corrugator supercilia muscle (CSM) and procerus muscles are the main targets. Although there have been many studies on the treatment of glabellar frown lines, no study has confirmed the dynamic movement under ultrasonography (US). This study examined and evaluated dynamic muscle movements under US, thereby providing more effective BoNT injection guidelines for glabellar frowning. Glabellar frowning was categorized as either Type A or B. Type A is the general frowning pattern in which vertical wrinkles are made by contracting the CSM and procerus muscles (81%, n = 13). On US images, the procerus muscle thickens and the bilateral CSMs contract. Type B is an upward frowning pattern demonstrating upward elevation of vertical wrinkles due to hyperactive contraction of the frontalis muscle during frowning (19%, n = 3). On US images, the hypoechoic frontalis muscle thickens, forming horizontal forehead lines. After BoNT injection into the CSM and frontalis muscle but not the procerus muscle, Type B patterns showed improvements in the vertical crease and horizontal forehead line. Both types showed improvement in glabellar frown lines after conventional injection, but the horizontal forehead line did not improve in Type B. Type B wrinkles improved after additional injections into the frontalis muscle. This study provided novel anatomical findings related to the injection of glabellar frown lines with BoNT. Preliminary analysis and optimized procedures using US will enable more effective and safer injections.