Sihler-stain study of buccal nerve distribution and its clinical implications

Requirement of the Preservation of Mental Nerve During the Transfer of Depressor Anguli Oris Composite Flap

Objectives

Reconstruction of wide lower lip defects is still a challenging subject in terms of obtaining functional and aesthetically acceptable results. Lower lip reconstruction with depressor anguli oris muscle was first described by Tobin in 1983. Since the sensory innervation of this composite muscle flap is provided by the mental nerve, it has been advocated that the mental nerve should be preserve during flap elevation. However, no further study has been conducted about this subject since then.

Methods

Sixteen patients with lower lip mass have undergone excisional biopsy. The resultant defects were higher than 30% of the total lower lip. All the defects were reconstructed with Depressor anguli oris composite flaps. In 9 of the patients, the mental nerve was preserved and included to the flap, while in remaining patients it was sacrificed. The results were evaluated in terms of sensation, function, and aesthetic appearance.

Results

In unilaterally reconstructed cases, the results regarding sensation and general complications were similar. However, in bilaterally reconstructed cases, especially where the mental nerve was preserved, the limited arc of rotation has resulted in functional complications, such as whistle deformity in the midline and drooling.

Conclusion

The mental nerve does not just limit the arc of rotation of the Depressör anguli oris composite flap but also remains as a potential route for metastasis via perineural invasion. Preservation and inclusion of the mental nerve during reconstruction with Depressor anguli oris flap do not provide any superior outcome; on the contrary, these results in various unfavorable events make this flap a poor option. The skin and mucosa of the DAO flap are innervated by the buccal branch of the trigeminal nerve; thus, the mental nerve should not be preserved during surgery.

A Detailed Analysis of the Blood Supply to the Subscapularis Muscle

This study aimed to provide a comprehensive description of the arterial supply to the subscapularis (SSC) muscle. This will provide critical information for various surgical procedures. Ten specimens of embalmed Korean cadavers were dissected and subjected to modified Sihler's method to reveal the branching pattern of the arteries surrounding the subscapularis, and its intramuscular blood supply. The SSC muscle was generally supplied by branches from the subclavian artery (suprascapular artery, supraSA; circumflex scapular artery, CxSA; and dorsal scapular artery, dSA) and the axillary artery (subscapular artery, subSA; lateral thoracic artery, LTA; posterior circumflex humeral artery, PCxHA; and a branch of the axillary artery, AAbr). The anterior aspect of the muscle was supplied by the subSA, LTA, CxSA, supraSA, and AAbr. The posterior aspect of the muscle was supplied by the supraSA, PCxHA, and subSA. The dSA was more scarcely distributed than the other arteries. In two cases, the dSA supplied the portion of the muscle near the medial border of the scapular. The anterior side of the muscle tendon was supplied by the CxSA, and its posterior side was supplied by the PCxHA. The subSA can be considered to be the main branch supplying the SSA based on its distribution area of arteries. It was mostly situated within the lower region of the SSC. After distributing to the anterior surface of the SSC, some branches of the subSA reached the posterior surface as perforating branches. Clin. Anat. 32:642-647, 2019. © 2019 Wiley Periodicals, Inc.

Morphological analysis and three-dimensional reconstruction of the SMAS surrounding the nasolabial fold

BACKGROUND

The superficial musculoaponeurotic system (SMAS), a structure that has been discussed with some controversy, has a complex morphological architecture.

MATERIAL AND METHODS

Histological analysis was performed on tissue blocks of the nasolabial fold (NLF) collected postmortem from formalin-fixed bodies of one male and one female donor. Serial histological sections were made, stained and digitized. Three-dimensional reconstructions of the histological structures were performed. Specimen- and location-specific differences were determined. SEM analysis of the NLF tissue block was performed.

RESULTS

The NLF SMAS is a fibro-muscular, three-dimensional meshwork bolstered with fat cells. Two SMAS structure types were identified adjacent to the NLF. The cheek SMAS structure showed a regular, vertical and parallel alignment of the fibrous septa, building a three-dimensional meshwork of intercommunicating compartments. It changed its morphology, condensing while transiting the NLF and passing over to form an irregular structure in the upper lip region. SEM analysis demonstrated the connection between the fibrous meshwork and the fat cells. SMAS blood circulation expanded subcutaneously without perforating the fibro-muscular septa.

CONCLUSIONS

The NLF has a recognizable condensed cheek SMAS structure and represents the transition zone between the two SMAS types. Specimen-specific morphological differences necessitate individual planning and area-specific surgical procedures.

The course and distribution of the buccal nerve: clinical relevance in dentistry

BACKGROUND

The buccal branch of the mandibular division of the trigeminal nerve is commonly anaesthetized for dental procedures and may be damaged during surgery. Descriptions of the distribution of the buccal nerve (BN) in anatomical texts are generally lacking in detail and do not provide information about the extent of its variation between individuals. There are also commonly-held clinical beliefs about the BN that lack support from anatomical dissections.

METHODS

Detailed dissections of the course and distribution of the BN were performed in a sample of 12 hemi-heads from 11 edentulous and partially dentate human adult cadavers.

RESULTS

A broader distribution of the BN was found than described previously, with innervation extending to the lips in all cases. Approximately half of the lateral sides of the lips were innervated by the BN in two cases and approximately one-third of their lateral sides in the other 10 cases. Distribution of the BN to the lower lips was wider than to the upper lips.

CONCLUSIONS

Our findings provide a stronger anatomical basis to underpin clinical procedures involving the BN and indicate that some commonly-held clinical views about this nerve are not supported by anatomical evidence.

A Cadaveric Study of the Communication Patterns Between the Buccal Trunks of the Facial Nerve and the Infraorbital Nerve in the Midface

Most nerve communications reported in the literature were found between the terminal branches. This study aimed to clarify and classify patterns of proximal communications between the buccal branches (BN) of the facial nerve and the infraorbital nerve (ION).The superficial musculoaponeurotic system protects any communication sites from conventional dissections. Based on this limitation, the soft tissues of each face were peeled off the facial skull and the facial turn-down flap specimens were dissected from the periosteal view. Dissection was performed in 40 hemifaces to classify the communications in the sublevator space. Communication site was measured from the ala of nose.A double communication was the most common type found in 62.5% of hemifaces. Triple and single communications existed in 25% and 10% of 40 hemiface specimens, respectively. One hemiface had no communication. The most common type of communication occurred between the lower trunk of the BN of the facial nerve and the lateral labial (fourth) branch of the ION (70% in 40 hemifaces). Communication site was deep to the levator labii superioris muscle at 16.2 mm from the nasal ala. Communications between the motor and the sensory nerves in the midface may be important to increase nerve endurance and to compensate functional loss from injury.Proximal communications between the main trunks of the facial nerve and the ION in the midface exist in every face. This implies some specific functions in normal individuals. Awareness of these nerves is essential in surgical procedure in the midface.

Neurovascular structures of the mandibular angle and condyle: a comprehensive anatomical review

BACKGROUND

Various surgical interventions including esthetic surgery, salivary gland excision, and open reduction of fracture have been performed in the area around the mandibular angle and condyle. This study aimed to comprehensively review the anatomy of the neurovascular structures on the angle and condyle with recent anatomic and clinical research.

METHODS AND RESULTS

We provide detailed information about the branching and distributing patterns of the neurovascular structures at the mandibular angle and condyle, with reported data of measurements and proportions from previous anatomical and clinical research. Our report should serve to help practitioners gain a better understanding of the area in order or reduce potential complications during local procedures. Reckless manipulation during mandibular angle reduction could mutilate arterial branches, not only from the facial artery, but also from the external carotid artery. The transverse facial artery and superficial temporal artery could be damaged during approach and incision in the condylar area. The marginal mandibular branch of the facial nerve can be easily damaged during submandibular gland excision or facial rejuvenation treatment. The main trunk of the facial nerve and its upper and lower distinct divisions have been damaged during parotidectomy, rhytidectomy, and open reductions of condylar fractures.

CONCLUSION

By revisiting the information in the present study, surgeons will be able to more accurately prevent procedure-related complications, such as iatrogenic vascular accidents on the mandibular angle and condyle, complete and partial facial palsy, gustatory sweating (Frey syndrome), and traumatic neuroma after parotidectomy.

Surgical consideration of the anatomic origin of the risorius in relation to facial planes

BACKGROUND

Confusion exists as to the plane of the risorius with respect to the superficial musculoaponeurotic system (SMAS), the parotid fascia, and the masseteric fascia, which generally are considered origins of the risorius.

OBJECTIVES

The authors attempted to clarify the origin of the risorius by topographic examination and dissection, which would provide valuable anatomic information for flap dissection in facelift surgery.

METHODS

Detailed dissection was performed in the perioral region of 46 cadaveric specimens to discern the origin of the risorius in relation to the fascial layer. The anatomic aspects of the muscular arrangement and origin of the risorius were classified according to the location of attachment.

RESULTS

The risorius originated solely from the fascial layer superficial to the SMAS in 27 specimens (58.7%; type A). It originated solely from the masseter tendon in 3 specimens (6.5%; type B) and from the fascial layers, both superficial and deep to the SMAS, in 16 specimens (34.8%; type C).

CONCLUSIONS

The patterns of risorius origination identified in this study represent important anatomic reference information for flap dissection in facelift surgery.

Sihler staining study of anastomosis between the facial and trigeminal nerves in the ocular area and its clinical implications

INTRODUCTION

The trigeminal nerve (CN V) supplies mostly sensory innervation to the face, and the facial nerve (CN VII) conveys primarily motor fibers. The aim of this study was to elucidate their distributions and anastomoses.

METHODS

Fourteen specimens of hemisectioned faces were gathered from human cadavers and stained with Sihler staining.

RESULTS

The temporal (Tbr), zygomatic (Zbr), and buccal (Bbr) branches of CN VII formed trigeminofacial anastomoses in the ocular area. Communications were observed between the supraorbital nerve and the Tbr (85.7%), the infraorbital nerve and the Bbr (100%) and Zbr (28.6%), and the zygomaticofacial nerve and the Zbr (41.7%). Anastomoses were formed between the supratrochlear nerve and the Tbr (57.1%) and Bbr (50%), and the infratrochlear nerve and the Bbr (85.7%).

CONCLUSIONS

Motor and sensory axons to the face contribute to trigeminofacial anastomoses, which may play key roles in subtle movements of muscles of facial expression.