Extended effect after a single dose of type A botulinum toxin for asymmetric masseter muscle hypertrophy

Ultrasound-Guided Botulinum Toxin-A Injections into the Masseter Muscle for Both Medical and Aesthetic Purposes

With the increasing use of Botulinum toxin type A (BoNT-A) injections in the masseter muscles for both medical and aesthetic purposes, there is a constant need to continually enhance the efficacy of these treatments and reduce the risk of potential adverse events. This review provides an in-depth analysis of the masseter muscle's anatomical structure and essential landmarks and emphasizes the advantages of ultrasound (US) guidance in improving the precision of BoNT-A injections compared to conventional blind methods. The review is supplemented with comprehensive figures, including graphics, clinical images, and ultrasound visuals, to support the discussion. Potential complications such as paradoxical bulging, inadvertent injections into the risorius muscle or parotid gland, facial paralysis, and the risk of bone resorption are examined. Future research should aim at refining injection techniques and assessing the long-term effects of repeated treatments to ensure optimal patient care and safety.

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.

Obvious morphologic changes in the mandible and condylar cartilage after triple botulinum toxin injections into the bilateral masseter

INTRODUCTION

Nonsurgical treatments that can prevent or reduce the extent of the mandibular excess at an early stage are desirable. A single botulinum toxin (BTX) injection into the unilateral and bilateral masseter can regulate mandibular contour and condylar cartilage. However, BTX injection is frequency dependent when used in facelifts. This study aimed to evaluate the effect of BTX injection into the bilateral masseter at different frequencies on the mandibular contour and condylar cartilage.

METHODS

In the present study, 24 female Sprague Dawley rats (4 weeks old) were divided into 3 groups: control, single injection, and triple injection. Contour measurement of the mandible was carried out by radiographic imaging. Microcomputerized tomography was performed to determine the change in bone volume in the subchondral bone. Hematoxylin and eosin staining was used to observe the morphologic changes of condylar cartilage. Immunohistochemistry was performed to detect the expression level of biomechanically sensitive factors, including transforming growth factor-β1, parathyroid hormone-related protein, SRY-box 9, and type II collagen.

RESULTS

Bone volume and/or total volume, trabecular number, and trabecular thickness of the mineralized cartilage and subchondral bone significantly decreased in the triple injection group when compared with the single injection group. Mandibular contour also diminished after increased BTX injection frequencies. Chondrocyte proliferation ability and the expression levels of transforming growth factor-β1, parathyroid hormone-related protein, SRY-box 9, and type II collagen significantly decreased in all BTX injection groups and more in the triple injection group.

CONCLUSIONS

Morphologic changes of the mandible and condylar cartilage become more obvious after increased BTX injection frequencies, suggesting that multiple BTX injections into the masseter of patients may relieve the severity of mandibular deformity at an early stage.

Botulinum Toxin in Aesthetic Medicine: Myths and Realities

Several formulations of Botulinum toxin serotype A (BoNT-A) for aesthetic indications are available, with numbers likely to increase. Preparations are not interchangeable, based on dose unit comparisons.

Consensus Recommendations for Treatment Strategies in Indians Using Botulinum Toxin and Hyaluronic Acid Fillers

BACKGROUND

Indians constitute one of the largest population groups in the world. Facial anthropometry, morphology, and age-related changes in Indians differ from those of other ethnic groups, necessitating a good understanding of their facial structure and the required aesthetic treatment strategies. However, published recommendations specific to Indians are few, particularly regarding combination treatment.

METHODS

The Indian Facial Aesthetics Expert Group (19 dermatologists, plastic surgeons, and aesthetic physicians with a mean 15.5 years' aesthetic treatment experience) met to develop consensus recommendations for the cosmetic facial use of botulinum toxin and hyaluronic acid fillers, alone and in combination, in Indians. Treatment strategies and dosage recommendations (agreed by ≥ 75% of the group) were based on results of a premeeting survey, peer-reviewed literature, and the experts' clinical experience.

RESULTS

The need for combination treatment increases with age. Tear trough deficiency is the most common midface indication in Indian women aged 20-40 years. In older women, malar volume loss and jowls are the most common aesthetic concerns. Excess medial soft tissue on a relatively smaller midface precedes age-related sagging. Hence, in older Indians, fillers should be used peripherally to achieve lift and conservatively in the medial zones to avoid adding bulk medially. The shorter, wider lower face requires 3-dimensional correction, including chin augmentation, to achieve increased facial height and the oval shape desired by most Indian women.

CONCLUSIONS

These recommendations give physicians treating Indians worldwide a better understanding of their unique facial characteristics and provide treatment strategies to achieve optimal aesthetic outcomes.

Botulinum toxin in the management of head and neck disorders

Botulinum toxin is a polypeptide protoxin synthesized by Clostridium botulinum that results in localized reduction of muscle activity by inhibiting acetylcholine release at the neuromuscular junction. In 2004, the US Food and Drug Administration approved its application in the treatment of various medical conditions, such as facial wrinkles, strabismus, cervical dystonia, blepharospasm, and hyperhidrosis. Later, its application extended to improving dental esthetics and gummy smile. It was found to be a safe and effective alternative to medical therapy to treat various head and neck disorders that have a neurologic component. In this review, we will highlight the mechanism of action and therapeutic benefits of botulinum toxin in the management of head and neck disorders.