Anatomical analysis of the distribution patterns of occipital cutaneous nerves and the clinical implications for pain management.

PURPOSE: Establishing the distribution patterns of occipital cutaneous nerves may help us understand their contribution to various occipital pain patterns and ensure that a proper local injection method for treatment is employed. The aim of this study was to demonstrate the detailed distribution patterns of the greater occipital nerve (GON), lesser occipital nerve (LON), and third occipital nerve (TON) using the modified Sihler's staining technique. METHODS: Ten human cadavers were manually dissected to determine the nerve distributions. Specimens from eight human cadavers were treated using the modified Sihler's staining. RESULTS: In all cases, distinct GON branches proceeded laterally and were intensively distributed in the superolateral area from their emerging point. Very thin twigs were observed at the middle-trisected area, which had a fan-like shape, in the middle-upper occipital region. CONCLUSION: The LON and TON distribution areas were biased to the lateral side below the superior nuchal line, although these nerves exhibited multiple interconnections or overlapping areas with the GON. Furthermore, a nerve rarified zone in the shape of an inverted triangle was identified in the middle occipital area. Our findings improve our understanding of the occipital nerve anatomy and will aid in the management of occipital pain in clinical practice.

Topographic Anatomy of the Infraorbital Artery and Its Clinical Implications for Nasolabial Fold Augmentation.

BACKGROUND: Understanding the topography of the blood vessels distributed around the nasolabial fold region is essential for ensuring the safety of dermal filler injections into the nasolabial fold. The purpose of this study was to provide anatomical information on the infraorbital artery distribution and its relationship with the facial artery for use in clinical procedures involving filler injection during nasolabial fold augmentation. METHODS: The infraorbital artery was investigated in the nasolabial fold region divided into zones I to XII based on clock-hour meridians centered on the infraorbital foramen. The running layers of the infraorbital artery and infraorbital nerve were also compared in the infraorbital foramen. Changes in the infraorbital artery were observed according to vascular dominance of the facial artery. RESULTS: The infraorbital artery was divided into three main branches, palpebral, nasal, and labial infraorbital artery branches in 34.7, 100, and 100 percent of the specimens, respectively; with these branches of palpebral, nasal, and labial infraorbital artery observed most commonly in zones I, V, and VI, respectively. Analysis of the bilateral facial artery topography revealed that its vascular dominance was observed in 19.4 percent. The infraorbital artery was thicker and had a wider distribution on the nondominant side of the facial artery, whereas the nasal infraorbital nerve anastomosed with the facial artery in the lateral nasal region in 57.1 percent. CONCLUSION: Investigating and verifying the vascular structure regarding its interactions with the facial artery and infraorbital artery will provide critical information to physicians performing facial surgery and cosmetic procedures.

Anatomical consideration of the occipital cutaneous nerves and artery for the safe treatment of occipital neuralgia.

There is no standardized approach to the greater occipital nerve (GON) block technique for treating occipital neuralgia. The aim of the present study was to validate the previously-suggested guidelines for conventional injection techniques and to provide navigational guidelines for safe GON block. The GON, lesser occipital nerve (LON) and occipital artery (OA) were carefully dissected in the occipital region of embalmed cadavers. Using a 3 D digitizer, the GON, LON, and OA were observed on the two reference lines. The distances between the landmarks were recorded and statistically analyzed. On the superior nuchal line, the mean distances between the external occipital protuberance (EOP) and the most medial branch of the GON was 33.5 mm. The mean distance between the EOP and the most medial branch of the OA was 37.4 mm. On the EOP-mastoid process (MP) line, the GON was on the medial third and the LON the lateral third of the EOP-MP line. The safe injection points on the EOP-MP line are about 3 cm from the EOP, 1 cm inferior parallel to the EOP-MP line, and about 3 cm away from the MP. Clin. Anat. 31:1058-1064, 2018. © 2018 Wiley Periodicals, Inc.

Stereotactic topography of the greater and third occipital nerves and its clinical implication.

This study aimed to provide topographic information of the greater occipital (GON) and third occipital (3ON) nerves, with the three-dimensional locations of their emerging points on the back muscles (60 sides, 30 cadavers) and their spatial relationship with muscle layers, using a 3D digitizer (Microscribe G2X, Immersion Corp, San Jose CA, USA). With reference to the external occipital protuberance (EOP), GON pierced the trapezius at a point 22.6 ± 7.4 mm lateral and 16.3 ± 5.9 mm inferior and the semispinalis capitis (SSC) at a point 13.1 ± 6.0 mm lateral and 27.7 ± 9.9 mm inferior. With the same reference, 3ON pierced, the trapezius at a point 12.9 ± 9.3 mm lateral and 44.2 ± 21.4 mm inferior, the splenius capitis at a point 10.0 ± 5.3 mm lateral and 59.2 ± 19.8 mm inferior, and SSC at a point 11.5 ± 9.9 mm lateral and 61.4 ± 15.3 mm inferior. Additionally, GON arose, winding up the obliquus capitis inferior, with the winding point located 52.3 ± 11.7 mm inferior to EOP and 30.2 ± 8.9 mm lateral to the midsagittal line. Knowing the course of GON and 3ON, from their emergence between vertebrae to the subcutaneous layer, is necessary for reliable nerve detection and precise analgesic injections. Moreover, stereotactic measurement using the 3D digitizer seems useful and accurate for neurovascular structure study.

An anatomical study of the risorius in Asians and its insertion at the modiolus.

PURPOSE: Detailed explanations of the insertion, interaction patterns, and arrangement of the risorius muscle fibers at the modiolus have still not been clearly shown. The aim of this study is to clarify the arrangement of the risorius muscle by means of topographic examination, and to evaluate the anatomical variations in its attachments and pattern of shape to other perioral muscles, and eventually to understand the various features of the facial animation of Asians. MATERIALS AND METHODS: Eighty embalmed Korean and Thai adult hemifaces from cadavers of both genders were dissected in this study. Detailed dissection at the modiolus revealed the insertion of the risorius muscle in relation to its attachments and fiber interaction forms. RESULTS: When categorized into three common anatomical types--zygomaticus risorius (ZR), platysma risorius (PR), and triangularis risorius (TR). PR was most common with 45 % (36 cases) frequency. Risorius muscle also inserted into the modiolus in three distinct layers in relation to the depressor anguli oris: superficial, flush, and deep. Superficial attachment was most commonly found with 56.3 % (45 cases) frequency. CONCLUSIONS: These results will provide critical information for future planning and performing of reconstructive, reanimation, and cosmetic surgical procedures for cases such as developmental defect, facial trauma, facial muscle paralysis, and restoring the natural personal appearances.

Three-dimensional courses of zygomaticofacial and zygomaticotemporal canals using micro-computed tomography in Korean.

The zygomatic nerve (ZN), which originates from the maxillary nerve at the pterygopalatine fossa, enters the orbit through the inferior orbital fissure. Within the lateral region of the orbit, the ZN divides into the zygomaticofacial (ZF) and zygomaticotemporal (ZT) nerves. The ZF and ZT nerves then pass on to the face and temporal region through the zygomaticoorbital foramen and enter their own bony canals within the zygomatic bone. However, multiple zygomaticofacial and zygomaticotemporal canals (ZFCs and ZTCs, respectively) can be observed, and their detailed intrabony courses are unknown. The aim of this study was clarify the three-dimensional intrabony courses and running patterns of the ZFCs and ZTCs, both to obtain a detailed anatomical description and for clinical purposes. Fourteen sides of the zygomatic bones were scanned as two-dimensional images using a micro-computed tomography (CT), with 32-µm slice thickness. Intrabony structures of each canals were three-dimensionally reconstructed and analyzed using Mimics computer software (Version 10.01; Materialise, Leuven, Belgium). We found that some ZTC was originated from ZFC. In 71.4% of the specimens, the ZTC(s) divided from the intrabony canal along the course of the ZFC(s). In other cases, 28.6% of ZTCs were opened through each corresponding ZT foramen. Zygomaticofacial canal originates from zygomaticoorbital foramen, divided into some of ZTCs, and is finally opened as ZF foramen. This new anatomical description of the intrabony structures of the ZFC(s) and ZTC(s) within the zygomatic bone by micro-CT technology provided helpful information to surgeons performing clinical procedures such as Le Fort osteotomy and reconstructive surgeries in the midface region.

Histomorphologic approach for the modiolus with reference to reconstructive and aesthetic surgery.

The modiolus is strongly associated with facial expression, beauty, and aging, and so it is often viewed as the main facial landmark, both functionally and aesthetically. This study examined the modiolus and the surrounding structures histomorphologically with the aim of providing useful information for reconstructive and aesthetic surgery. Nineteen embalmed cadavers (38 hemifaces; 8 males and 11 females; mean age at death, 66.9 years) were examined in this study. For macroscopic observations, the modiolus and facial artery in the perioral region of 28 hemifaces were revealed by meticulous dissection. The modiolus and its surrounding structures were then prepared from 12 hemifaces for routine histology and stained with hematoxylin-eosin and Masson trichrome. A tendinous tissue nodule in the modiolus was found in 21.4% of cases (ie, 6 hemifaces). The facial artery passed approximately 1 mm lateral to the lateral border of the modiolus. In the central region of modiolus, which was an area of convergence of muscle fibers, the tendinous structure appeared as dense irregular collagenous connective tissue. Particularly in the middle layer between the skin and the oral mucosa, it appeared as a dense, compact, and prominent shape horizontally. The finding of the existence of a tendinous structure in the central region of the modiolus, which could act as an anchor for the converging facial muscles, is expected to provide critical information in the field of facial plastic surgery.

Topography of the submental artery that should be considered in bleeding during dentoalveolar surgery.

The purpose of the present study was to provide precise data regarding the branching pattern of the submental artery, which should be considered in occasions of bleeding during various dentoalveolar surgical procedures of the mandible, such as implant surgeries, tori removal, and iatrogenic injuries. Twenty-six embalmed adult hemifaces from Korean cadavers were used in this study. The vertical distance, horizontal distance, and diameter of the submental artery were measured from the site of the first premolar to the third molar. In cases where there was penetration of the mylohyoid muscle by the main branches of the submental artery, the same items were measured at that point. The vertical distance between the submental artery and the inferior border of the mandible decreased toward the premolar, whereas the horizontal distance from the lingual plate of the mandible increased gradually as it traveled in the anterior direction. The diameter of the artery narrowed slightly toward the premolar. The main branches of the submental artery perforated the mylohyoid muscle in 14 (54%) of the 26 specimens. As a result of this study, the submental artery is located higher from the inferior border and closer to the lingual plate of the mandible in the region of the molar than that of the premolar. Therefore, clinicians should be more careful of bleeding when performing surgery in the molar region compared with the premolar region. Where the mylohyoid muscle is perforated by the main branches of the submental artery, its point of insertion can be observed in diverse locations.

Intramuscular nerve distribution pattern of the adductor longus and gracilis muscles demonstrated with Sihler staining: guidance for botulinum toxin injection.

INTRODUCTION: The aims of this study were to clarify the intramuscular branching patterns and arborizing area of hip adductor muscles with reference to surface landmarks on the thigh and to thus suggest effective and safe injection points for botulinum neurotoxin (BoNT). METHODS: Ten gracilis and 10 adductor longus specimens were subjected to Sihler staining to reveal intramuscular nerve arborization patterns, and findings were matched with and referred to surface landmarks. Using these results, we determined the optimal location for BoNT injection in hip adductors in relation to the long axis of the femur. RESULTS: The corrected, most dense areas of innervation in adductor longus and gracilis were typically 30-50% and 40-50% from the anterior superior iliac spine (ASIS) along the vertical line of the femur, respectively. CONCLUSIONS: The most effective and safest point for BoNT injection into adductor muscles appears to be between 35% and 50% from ASIS, where neuromuscular junctions are most densely distributed.