The mental artery: anatomical study and literature review

Filling the Gap: Facial Anatomy and Safe Lower Lip Injection Practices

Background/Objectives: Anatomical knowledge of the arterial supply to the lower face is critical to prevent unnecessary harm to patients seeking cosmetic procedures, particularly lower lip dermal filler injections. Our study sought to characterize the prominent vascular structures of the lower lip: inferior labial (ILA), labiomental (LMA) and mental (MA) arteries. Methods: Forty-eight hemiface specimens from 30 formalin-embalmed donors were utilized in this study. Dissection was performed of the LMA, ILA, and MA to determine their diameter, branching pattern for characterization, and to assess their supply to the lip distally. Results: The ILA (mean diameter, 1.5 ± 0.49 mm) was found to be prevalent in 90% of sampled donors. The LMA (1.2 ± 0.53 mm) was found in 75% of donors. All 48 hemifaces were found to have a MA (1.6 ± 0.51 mm). 88% of ILAs, 43% of LMAs, and 96% of MAs were identified as directly supplying the lower lip. Mean location of the MA as it supplied the lower lip was determined to be (-17 mm, -8.2 mm) and (20 mm, -8.1 mm) in the left and right hemifaces, respectively. F-Test for variance found no significant differences amongst the horizontal (p = 0.82) and vertical distances (p = 0.41) bilaterally. Conclusions: Our findings demonstrate the high variability in vascular supply of the lower lip, suggesting the need for high-resolution ultrasound guidance and the integration of anatomical training within injection courses for the safe injection of dermal fillers.

Unilateral double facial artery: an anatomic variant and clinical implications

Background

This paper reports a rare anatomical variant of the facial artery (FA) - namely, a double FA pattern - which has significant implications in a wide range of surgical and aesthetic medicine disciplines.

Case

The study involves a case report and literature review of the FA and its variants. The case is that of a 61-year-old female cadaver with a unilateral FA variant branching pattern discovered during a cadaveric dissection for an anatomy course.

Discussion

The dissection revealed an unusual supply of the typical FA distribution by two separate branches from either side of the maxillary artery. The first branch, termed FA1, followed a typical FA course arising from the external carotid to supply the lower portion of the face via lingual, inferior labial, and mental arterial branches. The second branch, termed FA2, arose superior to the maxillary artery near the origin of a typical transverse facial artery, to supply the upper portion of the face via superior labial, lateral nasal, and angular arterial branches. No direct communication between the two branches was observed grossly via dissection. The observed branching pattern has not previously been reported in literature and has critical implications for surgical planning and intervention.

Conclusion

This study emphasizes the importance of understanding variant FA anatomy in procedures requiring precise anatomical knowledge of arterial supply to the face. Duplicate and/or secondary facial arteries necessitate careful consideration for their potential consequences on the success of surgery of the head and neck, dermal fillers, and embolization for epistaxis procedures.

The inferior alveolar nerve and its relationship to the mandibular canal

Previous work on the mandibular canal, mental foramen, and mandibular foramen has focused on humans and some other non-primate mammals (with small sample sizes), but little work has investigated the mandibular canal and inferior alveolar nerve (IAN) across primates. However, it is important to understand the relationship between the IAN and mandibular canal due to the IAN's close relationship to the teeth and mastication, and thus dietary adaptations. While it is assumed that most bony canals within the skull grow around and form to pre-existing nervous structures, this relationship has never been validated for the IAN and mandibular canal. MicroCT scans of 273 individuals (131 females, 134 males, and 8 unknown sex) from 68 primate species and three mammalian outgroups, and diceCT scans of 66 individuals (35 females, 23 males, and 8 unknown sex) from 33 primate species and the same mammalian outgroups were used to create 3D models of the IAN and mandibular canal from which cross-sectional areas were taken at various points on the structures. Using qualitative descriptions, phylogenetic generalized least squares analysis, and phylogenetic ANOVAs, we were able to establish three main conclusions: (1) the mandibular canal is most often not a defined canal within the mandible of primates, (2) when the canal can be identified, the IAN does not comprise most of the space within, and (3) there are significant relationships between the IAN and the corresponding canals, with most showing isometry and the mental foramen/nerve showing negative allometry.

The notch of the mandible: what do different fields call it?

The bony notch on the inferior border of the mandible, anterior to the attachment of the masseter muscle, where the facial vessels commonly pass, has been called different names in the literature, e.g., premasseteric notch, antegonial notch, and notch for the facial vessels. Interestingly, various disciplines have leaned toward different names for this notch. Therefore, to aid in consistent communication among professionals, the present study aimed to analyze usage of these varied terms and make recommendations for the best terminology. Based on the adjacent anatomical structures used to name this notch, three groups were analyzed in this study, a group using masseter in the term, a group using gonion in the term, and a group using facial vessels in the term. A literature search found that the group using gonion in the term was found most in the literature. The orthodontics field used gonion in the term the most (29.0%: 31/107) followed by the oral and maxillofacial surgery field (14.0%: 15/107), the plastic surgery field (4.7%: 5/107), and the anatomy field (3.7%: 4/107). The dental field used gonion in this term the most (43.9%: 47/107) and the medical field used facial vessels in the term the most (33.3%: 6/18). Based on these results, the use of gonial terms for this notch seems to be preferred.

A rare anatomical variation of the submental artery

The submental artery usually runs anteriorly on the inferior surface of the mylohyoid muscle, giving branches to that muscle and to the anterior belly of the digastric muscle, finally supplying the submental skin. Branches of it often perforate the mylohyoid muscle and enter the sublingual space. During a routine anatomy dissection, we encountered a case in which the main trunk of the submental artery perforated the mylohyoid muscle, where the sublingual artery usually runs. No branches coursed anteriorly to supply the submental skin. To our knowledge, this submental artery variation has not been reported in the English literature. Any surgical procedure in the submandibular area, such as the axial pattern submental local flap, requires knowledge of such arterial variations.