Why do marionette lines appear? Exploring the anatomical perspectives and role of thread-based interventions.

The pathogenesis of marionette lines involves a complex interplay of anatomical, physiological, and age-related factors leading to the development of wrinkles around the oral commissures. This exploration delves into the distinct anatomical predispositions observed among different ethnicities, emphasizing the role of compact modiolus structures and muscle compositions. Notably, individuals of East Asian descent exhibit inherent facial structures that predispose them to pronounced sagging around the oral commissures during aging. The emergence of distinct facial lines, such as the commissural line and the melolabial fold, contributes to the formation of marionette lines. This specific wrinkle pattern, resembling a marionette puppet's mouth contours, is influenced by various factors like bone resorption, gravitational forces, fat compartment variations, muscle compression, ligament tethering, and skin aging. Treatment strategies for marionette lines encompass diverse interventions, including filler injections, botulinum neurotoxin, surgeries targeting fat reduction, thread lifting, and volumizing fillers. These approaches aim to address the underlying causes and mitigate the appearance of marionette lines. Botulinum neurotoxin injections, for instance, weaken specific facial muscles, reducing downward strain and aiding in tissue retraction. Anatomical considerations during procedures are crucial to avoid nerve or vascular damage. Delicate manipulation and precise entry points are essential to prevent inadvertent injuries, particularly concerning blood vessels like the facial artery and nerves like the mental nerve. Technical guidelines for procedures targeting marionette lines involve specific techniques like cogged thread reverse methods and volumizing thread placements. Attention to entry points, tissue engagement, and the direction of threads is crucial for effective treatment outcomes, minimizing complications, and ensuring patient safety.

Anatomical and Ultrasonographic Analyses of the Levator Labii Superioris Alaeque Nasi Muscle at the Level of the Nasal Ala / Análisis Anatómico y Ecográfico del Músculo Elevador Nasolabial a Nivel del Ala Nasal

SUMMARY: We aimed to determine the width of the levator labii superioris alaeque nasi muscle (LLSAN) at the level of the nasal ala through cadaveric dissections and ultrasonography (US), to provide essential anatomical information for use during both invasive and noninvasive procedures in the nasal ala region. The LLSAN was investigated in the 40 hemifaces of 20 Korean cadavers, comprising 10 males and 10 females with a mean age of 73.6 years. The LLSAN width of the 40 specimens at the level of the midpoint of the nasal ala was 5.02±2.35 mm (mean±standard deviation), and ranged from 1.45 mm to 10.11 mm. The LLSAN widths were 5.96±2.36 mm and 3.93±1.89 mm in males and females, respectively, with ranges of 2.40-10.11 mm and 1.45-6.96 mm, respectively. The LLSAN widths on the left and right sides were 4.77±2.72 mm and 5.26±1.99 mm, respectively. The proportions of the LLSAN fibers inserting into the nasal ala and upper lip were similar in 13 specimens (32.5 %), while more fibers inserted into the nasal ala in 11 specimens (27.5 %) and more fibers inserted fibers of the LLSAN into the upper lip in 16 specimens (40 %). When clinicians need to target or avoid the LLSAN, the present width and range data can be helpful for ensuring the efficacy and safely of both invasive and noninvasive procedures. In addition, the possibility of asymmetry in the width of the LLSAN in the nasal ala region should be confirmed by US before performing such procedures.

Nuestro objetivo fue determinar el ancho del músculo elevador nasolabial (MENL) a nivel del ala nasal mediante disecciones cadavéricas y ecografía, para proporcionar información anatómica esencial, para su uso durante procedimientos invasivos y no invasivos, en la región del ala nasal. El MENL se estudió en 40 hemicaras de 20 cadáveres coreanos (10 hombres y 10 mujeres) con una edad media de 73,6 años. El ancho de MENL de las 40 muestras a nivel del punto medio del ala nasal fue de 5,02 ± 2,35 mm (media ± desviación estándar) y osciló entre 1,45 mm y 10,11 mm. Los anchos de MENL fueron 5,96 ± 2,36 mm y 3,93 ± 1,89 mm en hombres y mujeres, respectivamente, con rangos de 2,40 a 10,11 mm y 1,45 a 6,96 mm, respec- tivamente. Los anchos de MENL en los lados izquierdo y derecho fueron 4,77 ± 2,72 mm y 5,26 ± 1,99 mm, respectivamente. Las proporciones de fibras de MENL que se insertaban en el ala nasal y en el labio superior fueron similares en 13 muestras (32,5 %), mientras que se insertaron más fibras en el ala nasal en 11 muestras (27,5 %) y además, se insertaron fibras de MENL en el labio superior en 16 ejemplares (40 %). Cuando los médicos necesitan apuntar o evitar el MENL, los datos actuales de ancho y rango pueden ser útiles para garantizar la eficacia y seguridad de los procedimientos, tanto invasivos como no invasivos. Además, la ecografía puede ser utilizada para confirmar una posible asimetría en el ancho del MENL en la región del ala nasal antes de realizar los procedimientos.

Ultrasonographic findings of facial muscles in patients with severe facial palsy who showed no improvement for more than 3 months on acute stage.

INTRODUCTION/AIMS: The study aimed to visualize the changes in the facial muscles of patients with severe facial palsy who showed no improvement for more than 3 months on acute stage. METHODS: The 102 patients with severe facial palsy over House-Brackmann grade IV or an 80% degenerative ratio on ENoG at the initial examination, who showed no improvement for more than 3 months on acute stage were indicated to undergo ultrasonography of the face to evaluate the facial muscles. RESULTS: Muscular degeneration was observed in 537/918 muscles (58.5%). Muscle volume shrinkage was observed in 209/918 muscles (22.8%). Fascial adhesions were observed in 209/918 muscles (22.7%). Among all the muscles assessed for degenerative changes, zygomaticus major/minor was the most affected by degenerative changes (91.2%). Degenerative changes were observed in the levator labii superioris muscle in 84.3% patients. The shrinkage was most frequently observed in the zygomaticus major muscle (61/102 patients [59.8%]), followed by the zygomaticus minor muscle (43.1%). Shrinkage of the levator labii suprioris was observed in 24.5% patients. The zygomaticus major/minor muscle had the highest proportion of fascial adhesions in 61.8% and 66.7% patients respectively. The levator labii suprioris muscle showed the lowest proportion of fascial adhesions, with only 7.8% patients being affected. DISCUSSION: This study confirmed that the zygomaticus major, zygomaticus minor, and levator labii suprioris muscles, which raise the corner of the mouth, are the first to degenerate in patients with severe facial paralysis. This study demonstrated that ultrasonography is a simple and non-invasive examination for facial paralysis.

Objectifying the Role of the Depressor Anguli Oris Muscle Using High-Resolution Ultrasound: A Prospective Study.

BACKGROUND: In the setting of facial palsy, synkinesis of the depressor anguli oris (DAO) muscle is a common pathology, impairing dynamic and resting facial symmetry.In this prospective study, the authors used high-resolution ultrasound (HRUS) to evaluate the morphologic features of DAO and to quantify bilateral differences in DAO cross-sectional diameter (CSD) in individuals with unilateral synkinesis. METHODS: From June of 2020 to May of 2021, 30 patients (19 women, 11 men) with clinically diagnosed unilateral synkinesis underwent evaluation with HRUS. DAO CSD was measured bilaterally, 1 cm inferior to the modiolus, in both the resting and smiling positions. RESULTS: The Sunnybrook Facial Grading System Synkinesis Score was 6.20 ± 2.48 (range, 0 to 10). DAO CSD at rest measured 2.41 ± 0.67 mm (range, 1.40 to 4.00 mm) on the control side and 2.66 ± 0.98 mm (range, 1.60 to 5.10 mm) on the affected side. On the control side, DAO CSD was reduced by -0.19 ± 0.43 mm (range, -1.10 to 1.12 mm) during smiling. In contrast, the synkinetic DAO CSD increased by 0.64 ± 0.38 mm (range, 0.00 to 1.59 mm) ( P < 0.001) with animation. The pattern of increased CSD in synkinetic DAO muscles and decreased or unchanged CSD on the control side during smiling was identified in 70% of patients. CONCLUSIONS: HRUS demonstrates increased CSD in synkinetic DAO muscles during active smiling. The opposite is true for DAO muscles on the control side, which exhibit decreased CSD with animation. HRUS can be performed preoperatively to objectify DAO dysfunction and guide targeted therapy. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, IV.

High-Resolution Ultrasound of Facial Muscles: Sonoanatomy, Scanning Technique, and Pathological Cases.

The aim of the present work is to review the sonographic appearance of facial muscles with high-frequency transducers and to illustrate a step-by-step scanning technique that enables an effective evaluation of them. In addition, we highlighted the clinical application showing some pathological cases demonstrated with ultrasound (US). The recent technological advances have greatly enlarged the potential of high-resolution US in the evaluation of the face. Furthermore, the clinical indications of this technique are expected to increase in the near future.

Application of 3-Dimensional Technology for Evaluating Muscular Type and Muscle-Fat Pad Mixed-Type Nasolabial Folds With Botulinum Toxin-A Treatment.

BACKGROUND: Botulinum toxin-A (BTX-A) is used in the treatment of nasolabial folds (NLFs). However, lighting and clinician subjectivity play a major role in evaluating the efficacy of this treatment. OBJECTIVES: By applying 3-dimensional (3D) technology, this study aimed to quantitatively evaluate the effects of BTX-A injection on muscular (M) and muscle-fat pad mixed-type (MF) NLFs. METHODS: BTX-A was injected into bilateral marked points on the NLFs, where the levator labii alaeque nasi, zygomaticus minor, and zygomaticus major pull the skin to form the NLF (2 U at each injection site). Pretreatment and posttreatment 3D facial images were captured with static and laughing expressions. The curvature, width, depth, and lateral fat volume of the NLFs were measured to compare the therapeutic efficacy for type M and MF NLFs. RESULTS: Thirty-nine patients with type M and 37 with type MF NLFs completed the follow-up data. In these patients, the curvature, width, and depth of the NLF showed a significant reduction at 1 month and gradually recovered at 3 and 6 months after treatment, with more significant improvement when laughing than when static. Variations compared to the pretreatment values of type MF were greater than those of type M at each time point. The lateral fat volume of the type MF NLF was significantly reduced (P < .05). CONCLUSIONS: 3D technology can quantitatively evaluate the effects BTX-A injection for treating type M and type MF NLFs. BTX-A is more effective on type MF than on type M NLFs.

Basic Consideration for Facial Aging: Age-Related Changes of the Bony Orbit and Orbicularis Oculi Muscle in East Asians.

BACKGROUND: Age-related changes in the periocular areas are mainly caused by anatomic changes of the bony orbit and orbicularis oculi muscle (OOM). To achieve effective rejuvenation, it is necessary to understand the age-related aspects of these anatomic changes. OBJECTIVES: The aim of this study was to analyze the configuration of the bony orbit and OOM with computed tomography (CT) and to evaluate the effects of aging on these structures. METHODS: A total of 220 orbits and OOMs of 110 Japanese participants (55 males, 55 females) aged 20 to 87 years were enrolled. The long diameter of the orbits, orbital ellipticity, OOM thickness, and OOM attachment to the inferior orbital rim were analyzed. These variables were statistically evaluated for their relationship with age. RESULTS: The long diameter of the orbit was significantly longer in those over than in those under 60 years, with a moderate and significant positive correlation between orbital ellipticity and age. OOM thickness and age showed a strong negative correlation. The degree of OOM attachment to the inferior orbital rim decreased significantly with age. CONCLUSIONS: This study showed that age-related changes of the bony orbit in Japanese individuals tended to be the same as those in Caucasians, but there were differences in the degree of changes observed. As a new finding in the Japanese population, the OOM not only thins with aging, but also gradually loosens from the facial bone. In the elderly, only the nasal side of the OOM was attached to the bone. In clinical applications, this knowledge could contribute to the development of cosmetic surgeries.

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.

Effect of dimensions on function: A 2-dimensional sonographic assessment to correlate facial muscle and smile type.

OBJECTIVE: The aim of this study was to measure the dimensions of the select facial muscles and correlate them with different types of smiles. METHODS: The study group included 30 South Asian adults (17 men and 13 women) aged between 24 and 30 years divided into 3 groups of 10 subjects each according to Rubin's classification of smile. The zygomaticus major, levator labii superioris, depressor anguli oris, and mentalis muscles were ultrasonographically evaluated. The length and thickness of the muscles were measured bilaterally. The data obtained were analyzed statistically. RESULTS: The maximum mean value thickness of the zygomaticus major was found in the canine smile group. The maximum mean value thickness of the depressor anguli oris and mentalis was seen in the full denture smile group. However, the thickness of the levator labii superioris muscle was similar between the different smile groups. There was no significant difference in the measurements of the length of the muscles between the right and the left sides. CONCLUSIONS: This study did not find any statistically significant correlation between the type of smiles described in Rubin's classification and the dimensions of the associated facial muscle.

Similarities and disparities between visual analysis and high-resolution electromyography of facial expressions.

Computer vision (CV) is widely used in the investigation of facial expressions. Applications range from psychological evaluation to neurology, to name just two examples. CV for identifying facial expressions may suffer from several shortcomings: CV provides indirect information about muscle activation, it is insensitive to activations that do not involve visible deformations, such as jaw clenching. Moreover, it relies on high-resolution and unobstructed visuals. High density surface electromyography (sEMG) recordings with soft electrode array is an alternative approach which provides direct information about muscle activation, even from freely behaving humans. In this investigation, we compare CV and sEMG analysis of facial muscle activation. We used independent component analysis (ICA) and multiple linear regression (MLR) to quantify the similarity and disparity between the two approaches for posed muscle activations. The comparison reveals similarity in event detection, but discrepancies and inconsistencies in source identification. Specifically, the correspondence between sEMG and action unit (AU)-based analyses, the most widely used basis of CV muscle activation prediction, appears to vary between participants and sessions. We also show a comparison between AU and sEMG data of spontaneous smiles, highlighting the differences between the two approaches. The data presented in this paper suggests that the use of AU-based analysis should consider its limited ability to reliably compare between different sessions and individuals and highlight the advantages of high-resolution sEMG for facial expression analysis.

Ultrasound Imaging of the Facial Muscles and Relevance with Botulinum Toxin Injections: A Pictorial Essay and Narrative Review.

High-resolution ultrasound is preferred as the first-line imaging modality for evaluation of superficial soft tissues, such as the facial muscles. In contrast to magnetic resonance imaging and computed tomography, which require specifically designated planes (axial, coronal and sagittal) for imaging, the ultrasound transducer can be navigated based on the alignment of facial muscles. Botulinum toxin injections are widely used in facial cosmetic procedures in recent times. Ultrasonography is recognized as a useful tool for pre-procedure localization of target muscles. In this pictorial review, we discuss the detailed sonoanatomy of facial muscles and their clinical relevance, particularly with regard to botulinum toxin injections. Furthermore, we have summarized the findings of clinical studies that report ultrasonographic imaging of facial muscles.

Reevaluation of the Layered Anatomy of the Forehead: Introducing the Subfrontalis Fascia and the Retrofrontalis Fat Compartments.

BACKGROUND: Novel imaging methods have provided new insights into the layered anatomy of the forehead. This study seeks to critically reevaluate the layered anatomy of the forehead by using ultrasound imaging and cadaveric dissection to provide an accurate anatomical description that can be used to guide safer surgical and minimally invasive frontal procedures. METHODS: This study used ultrasound imaging in a sample of 20 volunteers (12 female and eight male volunteers; aged 35.25 ± 4.2 years; body mass index, 24.28 ± 3.5 kg/m2) and cadaveric dissections of 16 body donors (12 female and four male body donors; aged 72.76 ± 9.5 years) to reevaluate the layered anatomy of the forehead. Layer-by-layer dissections and ultrasound-based measurements of the frontal structures guided conclusions. RESULTS: The following layered arrangement was identified: layer 1, skin; layer 2, superficial fatty layer; layer 3, suprafrontalis fascia; layer 4, orbicularis oculi and frontalis muscle (same plane); layer 5, a homogenous layer of fat [preseptal fat (in the upper eyelid), retro-orbicularis fat (deep to the orbicularis oculi muscle), and retro-frontalis fat (deep to the frontalis muscle); layer 6, subfrontalis fascia; layer 7, preperiosteal fat within the prefrontal space in the lower forehead and deep compartments in the upper forehead; and layer 8, periosteum. CONCLUSIONS: The results of this study add to the current understanding of the layered arrangement of the forehead. The combination of ultrasound imaging and cadaveric dissections provided evidence for a continuous fatty layer deep to the frontalis muscle.

Real-Time Ultrasound Imaging of the Tear Trough: Lessons Learned From Functional Anatomy.

BACKGROUND: The tear trough is one of the most challenging facial regions for soft-tissue filler injections. A thorough understanding of the underlying facial, muscular, and vascular anatomy is crucial to perform safe and effective tear trough injectable treatments. OBJECTIVES: The authors sought to evaluate the location and function of the angular vein in the tear trough in 3 different facial expressions: repose, smiling, and max. orbicularis oculi contraction. METHODS: Twenty study participants with a mean age of 48.3 years and mean BMI of 24.5 kg/m2 were investigated via functional ultrasound imaging. The diameter of the angular vein and the velocity and direction of venous blood flow were analyzed in repose, smiling, and during max. orbicularis oculi contraction. RESULTS: The angular vein was identified in 100% of the cases to travel inside the orbicularis oculi muscle (intra-muscular course) within the tear trough, whereas the angular artery was not identified in this location. The distance between the angular vein and the inferior orbital rim was (lateral to medial): 4.6 mm, 4.5 mm, 3.9 mm, and 3.8 mm. The caudally directed blood flow was in repose 10.2 cm/s and was 7.3 cm/s at max. orbicularis oculi muscle contraction; however, no blood flow was detectable during smiling. CONCLUSIONS: The diameter and the venous blood flow of the angular vein varied between the 3 tested facial expressions. Based on these anatomical findings, the deep injection approach to the tear trough is recommended due to the intramuscular course of the angular vein.

Atlas of voluntary facial muscle activation: Visualization of surface electromyographic activities of facial muscles during mimic exercises.

Complex facial muscle movements are essential for many motoric and emotional functions. Facial muscles are unique in the musculoskeletal system as they are interwoven, so that the contraction of one muscle influences the contractility characteristic of other mimic muscles. The facial muscles act more as a whole than as single facial muscle movements. The standard for clinical and psychosocial experiments to detect these complex interactions is surface electromyography (sEMG). What is missing, is an atlas showing which facial muscles are activated during specific tasks. Based on high-resolution sEMG data of 10 facial muscles of both sides of the face simultaneously recorded during 29 different facial muscle tasks, an atlas visualizing voluntary facial muscle activation was developed. For each task, the mean normalized EMG amplitudes of the examined facial muscles were visualized by colors. The colors were spread between the lowest and highest EMG activity. Gray shades represent no to very low EMG activities, light and dark brown shades represent low to medium EMG activities and red shades represent high to very high EMG activities relatively with respect to each task. The present atlas should become a helpful tool to design sEMG experiments not only for clinical trials and psychological experiments, but also for speech therapy and orofacial rehabilitation studies.

Clinical anatomy considerations on the muscular and vascular components of the midface by ultrasonographic imaging.

The first signs of face aging appear in the midface, so procedures such as botulinum toxin and filler injections are performed there. However, no guidelines based on clinical anatomy describing the muscular and vascular components in vivo have been published. The aim of this research was to describe the depths of the midface muscles and the locations of vessels using ultrasonographic (US) imaging. US was applied at 12 landmarks on the midface in 88 volunteers (49 males and 39 females; 19-36 years) to detect sex differences in the depths of muscles and the locations of the vessels. The depths of the orbicularis oculi (OOc), levator labii superioris alaeque nasi (LLSAN), and zygomaticus minor (Zmi) differed significantly with sex at P7 (p = 0.001) and P8 (p = 0.017), P1 (p = 0.028), and P4 (p = 0.035), respectively. The facial artery, facial vein, angular artery, angular vein, and perforator vessels were found at P9, P2 and P10, P1, P1 and P5, and P8, P11 and P12, respectively. The findings indicate that the depths of the OOc, LLSAN, and Zmi muscles differ between the sexes and that the vessels appear at specific landmarks. This information could help in developing anatomical guidelines for several procedures.

Desminopathy presenting as late onset bilateral facial weakness, with diagnosis supported by lower limb MRI.

A 63 year old male presented with a 20 year history of facial weakness and several years of nasal regurgitation and dysphonia. Examination revealed bilateral facial weakness with nasal speech. Serum creatine kinase was 918 U/L. Neurophysiological studies suggested a myopathy and biopsy of the left vastus lateralis showed serpentine basophilic inclusions in the sarcoplasm and strong oxidative enzyme activity suggesting mitochondria accumulation. The muscle MRI showed selective fatty replacement within semitendinosus, gastrocnemius and soleus indicative of a desminopathy. A heterozygous missense variant c.17C>G (p.Ser6Trp) was identified within DES, predicted to be pathogenic in silico and previously described in a family with distal limb weakness. There are no previous case reports of desminopathy presenting with facial weakness, to our knowledge. Diagnosis was suggested following myoimaging of clinically unaffected muscles. Our study highlights the importance of muscle MRI in the diagnostic evaluation of muscle disease and further expands the known phenotypic heterogeneity of desminopathies.

Effective Locations for Injecting Botulinum Toxin into the Mentalis Muscle; Cadaveric and Ultrasonographic Study.

The mentalis muscle is now considered key structures when performing procedures for rejuvenating the lower face. The aim of this study was to determine the anatomical morphology and location of the mentalis muscle and thereby provide anatomical information for facilitating clinical procedures designed to rejuvenate the lower face. Forty-four adult hemifaces from five Thai cadavers and 21 Korean cadavers were dissected to identify the locations of the mentalis muscle. Sixty-six hemifaces from 33 healthy young Korean subjects were included in an ultrasonographic study. The depth of the mentalis muscle below the skin surface, the thickness of the mentalis muscle, and the distance from the bone to the mentalis muscle were measured at the two points that were 5 mm lateral to the most-prominent point of the chin. The mentalis muscle was classified into two types based to its shape: in type A (86.4%, 38 of the 44 cases) it was dome shaped in three dimensions, while in type B (13.6%, 6 of the 44 cases) it was flat. The mentalis muscle was present mostly at the area 5-10 mm from the midsagittal line and 20-30 mm from a horizontal line connecting the mouth corners. The mentalis muscle was present between depths of 6.7 to 10.7 mm below the skin. This new information about the location of the mentalis muscle may help when identifying the most effective and safe botulinum toxin injection points and depths during esthetic procedures for weakened facial rhytides on the lower face.

The Course of the Angular Artery in the Midface: Implications for Surgical and Minimally Invasive Procedures.

BACKGROUND: Previous anatomic studies have provided valuable information on the 2-dimensional course of the angular segment of the facial artery in the midface and its arterial connections. The third dimension (ie, the depth of the artery) is less well characterized. OBJECTIVES: The objective of the present study was to describe the 3-dimensional pathway of the angular segment of the facial artery and its relationship to the muscles of facial expression. METHODS: The bilateral location and the depth of the midfacial segment of the facial artery was measured utilizing multi-planar computed tomographic image analyses obtained from contrast agent-enhanced cranial computed tomographic scans of 156 Caucasians aged a of 45.19 ± 18.7 years and with a mean body mass index of 25.05 ± 4.9 kg/m2. RESULTS: At the nasal ala, the mean depth of the main arterial trunk was 13.7 ± 3.7 mm (range, 2.7-25.0 mm), whereas at the medial canthus it was 1.02 ± 0.62 mm (range, 1.0-3.0 mm). This was reflected by the arteries' relationship to the midfacial muscles: at the nasal ala superficial to levator anguli oris in 62.0% but deep to the levator labii superioris alaeque nasi in 53.6%; at the medial canthus superficial to the levator labii superioris alaeque nasi in 83.1% and superficial to the orbicularis oculi in 82.7%. CONCLUSIONS: The results presented herein confirm the high variability in the course of the angular segment of the facial artery. Various arterial pathways have been identified providing evidence that, in the midface, there is no guaranteed safe location for minimally invasive procedures.