Electrophysiologic Frontalis Muscle Response Following Neuromodulator Injections

Understanding the Interplay Between Skin, Fascia, and Muscles of the Midface in Facial Aging

BACKGROUND

Surgical, minimally-invasive, and non-invasive aesthetic procedures try to ameliorate the signs of facial aging, but also focus on enhancing various individual features of beauty in each patient. Herein, the midface plays a central role due to its location but also its importance for the aesthetic perception and facial expression.

OBJECTIVE

To date, no study has investigated the interplay between facial muscles and its connecting subdermal architecture during facial aging to provide a more comprehensive understanding of the middle face.

MATERIALS AND METHODS

A total of 76 subjects, consisting of 30 males (39.5%) and 46 females (60.5%) with a mean age of 42.2 (18.7) years [range 19-80] and a mean BMI of 24.6 (3.7) kg/m2 [range 18-35], were enrolled in this investigation. Cutometry (skin aging), 3D skin displacement analyses (subdermal connective tissue aging), and sEMG (muscle aging) analyses were utilized.

RESULTS

The results revealed that overall skin firmness increased, and skin elasticity decreased (p < 0.001), sEMG signal of the investigated muscles decreased (p < 0.001), whereas midfacial mobility remained unaltered (p = 0.722).

CONCLUSION

The results of this study indicate that midfacial aging is a measurable effect when utilizing individual measurement modalities for assessing skin, subdermal fascia, and midfacial muscles. The function of midfacial muscles revealed a potential threshold effect, which is not reached during midfacial aging due to the unchanged soft tissue mobility at older age. However, to understand its clinical presentation all midfacial soft tissues need to be factored in and a holistic picture needs to be created.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes review articles, book reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 .

Investigating Facial Muscle Physiology Following Soft Tissue Filler Injections-A Surface-derived Electromyographic and Skin Vector Displacement Analytic Study

The use of hyaluronic acid-based soft tissue fillers has often been reported to modulate the muscle, that is, to cause myomodulation. To our knowledge, there has been so far no scientific study investigating the potential of hyaluronic acid-based soft tissue fillers to modulate or actually alter the function of facial muscles. To further assess this three-dimensional (3D) surface imaging and electromyography (EMG)-based prospective study investigated the changes of facial muscle contraction after injection of strategically placed hyaluronic acid-based soft tissue fillers to assess the actual validity of the term myomodulation. A total of 13 subjects with a mean age of 37.8 years (12 females, 1 male) were injected according to a predefined injection protocol. Surface EMG and 3D surface imaging were performed prior to the injection and 5 days after the injection. The results showed no significant change in the strength of the muscles (measured in μV) after injection of hyaluronic acid-based soft tissue fillers. However, horizontal and vertical skin displacement upon contraction of the zygomaticus major muscle changed significantly between baseline and follow-up, with a mean horizontal skin displacement increase from 3.2 to 4.1 mm. Upon contraction of the depressor anguli oris muscle, the horizontal skin displacement did not change significantly (2.15 vs. 2.05 mm), while vertical skin displacement increased significantly from 2.9 to 4.3 mm. The modification of the surrounding tissue caused an alteration of the vectorial skin displacement upon contraction of the muscle. A potential explanation could be the increased distance between the origin and insertion of the muscle due to the material deposition in the proximity of the relevant facial muscles, leading to a change of contraction vector.

Investigating the Contraction Pattern of the Zygomaticus Major Muscle and its Clinical Relevance: A Functional MRI Study

BACKGROUND

Our understanding of facial anatomy has significantly evolved, yet the detailed contraction patterns of facial muscles and their presentation during clinical imaging remain largely unexplored. Understanding the contraction patterns and visual presentation of these muscles, particularly the zygomaticus major could enhance pre-surgical facial assessments and the development of new treatment strategies.

METHODS

A total of 34 healthy young individuals (17 female, 17 male) with a mean age of 23.6 (2.4) years [range: 20-30] were investigated regarding the length, thickness, width, and angle of the zygomaticus major muscle in five different facial expressions (i.e., repose, anger, joy, surprise, and sadness) utilizing MR imaging.

RESULTS

Joyful expressions caused a reduction in muscle length to 85.6% of its original length and an increase in width (103.4%), thickness (108.4%), and facial angle (2.72°) when compared to that in repose, suggesting isotonic contraction. Conversely, expressions of anger, surprise, and sadness generally led to muscle stretching, seen through changes in length (98.9%, 104.3%, and 102.7%, respectively), width (98.8%, 96.5%, and 99.4%, respectively), and thickness (91.2%, 91.0%, and 102.7%, respectively), with variable alterations in facial angle (0.55°, 1.85°, and 1.00°, respectively) depending on the specific expression.

CONCLUSION

This MRI-based study indicates that the zygomaticus major muscle experiences isotonic contraction, characterized by decreased length and increased width and thickness. The findings underline the importance of muscle thickness as a reliable parameter in assessing facial muscle function and offer valuable guidance for practitioners in accurately evaluating muscle performance during different facial expressions.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 .

Efficacy and Safety of LetibotulinumtoxinA in the Treatment of Moderate and Severe Glabellar Lines in Females 35 to 50 Years of Age: Post Hoc Analyses of the Phase 3 Clinical Study Data

Background

Botulinum toxin type A (BoNT-A) injections continue to be widely used as a common treatment for both males and females. According to a recent survey conducted by the International Society of Plastic Aesthetic Surgeons, the majority of patients receiving these injections are females between the ages 35 and 50.

Objectives

A post hoc analysis was conducted to examine whether there were variances in the effectiveness and safety of letibotulinumtoxinA for treating vertical glabellar lines between the broader female study population and a particularly defined group of female participants aged 35 to 50.

Methods

For this post hoc analysis, data from females aged 35 to 50 were extracted and analyzed from the BLESS III study. In this Phase 3 clinical trial, 355 participants with moderate-to-severe glabella frown lines received either 20 U of letibotulinumtoxinA or a placebo. The study evaluated Glabella Line Severity (GLS) score, treatment onset, duration of effects, time to retreatment, and adverse events. A positive response was determined by achieving a GLS score of 0 or 1, as assessed by both patients and investigators, along with at least a 2-point improvement in GLS score relative to baseline at Week 4 after the injections.

Results

Composite responder rates for patients aged 35 to 50 receiving active treatment were significantly higher than for the remaining female population receiving active treatment at Weeks 1, 2, and 4. Females aged 35 to 50 showed higher rates of GLS improvement of ≥1 at Weeks 1, 2, 4, 8, 12, 16, and 20 compared with the remaining female population receiving active treatment. At Week 4, a higher percentage of females aged 35 to 50 achieved a GLS score of 0 upon maximum frowning compared with the remaining females. Females aged 35 to 50 had a shorter median time to onset of GLS improvement compared with the remaining female population. Safety assessments showed a low incidence of treatment-related adverse events in females aged 35 to 50.

Conclusions

LetibotulinumtoxinA showed significantly higher response rates in females aged 35 to 50 compared with other female patients at Weeks 1, 2, and 4. Response rates remained higher up to Week 16. The treatment demonstrated efficacy and safety in treating vertical glabellar lines in this patient group.

Level of Evidence 2

Aging of the Neck Decoded: New Insights for Minimally Invasive Treatments

BACKGROUND

Many signs of aging manifest in the neck region, including platysmal bands, excess skin, horizontal neck lines and decreasing contour of the neck. While the clinical signs of an aged neck are well-known, data determining the underlying aging process are limited.

OBJECTIVE

To decode aging of the neck.

MATERIALS AND METHODS

This prospective study investigated elasticity and firmness of skin, muscle activity and skin displacement upon muscular contraction in the neck in 77 young-, middle- and old-age individuals. Objective outcome measures, including 3-dimensional imaging, cutometry and surface electromyography, were utilized for all assessments.

RESULTS

Mean firmness of skin decreased significantly from young to old individuals (0.37 ± 0.13 mm, 0.30 ± 0.12 mm and 0.26 ± 0.12 mm in young, middle and old subjects, respectively; p < 0.001). Gross elasticity decreased significantly from 75.1 ± 13.0% in young subjects, to 64.53 ± 15.7% in middle-aged subjects and 55.79 ± 13.0% in old subjects (p < 0.001). The mean y-axis skin displacement increased from 2.48 ± 4.33 mm in young subjects, to 3.11 ± 4.49 mm in middle-aged subjects and 3.61 ± 5.38 mm in old subjects (p = 0.006). The mean signal-to-noise ratio decreased significantly from 16.74 ± 5.77 µV in young subjects, to 14.41 ± 4.86 µV in middle-aged subjects and to 12.23 ± 5.99 µV in old subjects (p < 0.001).

CONCLUSION

This study provides insights into the interplay between skin elasticity, muscular activity and the reflected movement of the skin of the neck. Appreciation of these age-related changes lays the fundament for aesthetic treatments in this delicate region.

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 .