Distribution patterns of infraorbital nerve branches and risk for injury.

BACKGROUND: During oral and head and neck surgery, oral vestibular incisions may require a transverse incision on the upper lip mucosa, resulting in possible sensory disturbances in the area innervated by infraorbital nerve (ION) branches. Although sensory disturbances are attributed to nerve injuries, anatomy textbooks have not showed the precise distribution patterns of the ION branches in the upper lip. Furthermore, no detailed study has been available on this issue. This study aimed to reveal the precise distribution patterns of ION branches in the upper lip by dissecting the detached upper lip and cheek area using a stereomicroscope. METHODS: During a gross anatomy course at Niigata University (2021-2022), nine human cadavers were examined with special focus on the relationship between ION branches in the upper lip and the layered structure of facial muscles. RESULTS: The ION branched to the inferior palpebral (IP), external and internal nasal, and superior labial (lateral and medial) nerves. The ION branches in the upper lip did not run in a horizontal pattern from outside to inside but showed a predominantly vertical pattern. Considering their course, incising the upper lip mucosa transversely may cause paresthesia of the ION branches. The internal nasal (IN) and medial superior labial (SLm) branches tended to penetrate the orbicularis oris and descend between this muscle and labial glands, whereas the lateral superior labial (SLl) branches tended to innervate the skin. CONCLUSIONS: These findings suggest that a lateral mucosal incision is recommended for oral vestibular incisions of the upper lip and that deeper incisions to the labial glands should be avoided when incising the medial side to preserve the ION during surgery from an anatomical point of view.

Spindle cell squamous cell carcinoma exhibiting prominent neutrophil phagocytosis: a case report.

BACKGROUND: Spindle cell squamous cell carcinoma is an uncommon variant of squamous cell carcinoma; its diagnosis is sometimes challenging because it histopathologically resembles neoplastic or reactive spindle cell lesions of mesenchymal origins. Here, we report a rare case of spindle cell squamous cell carcinoma exhibiting prominent neutrophil phagocytosis. CASE PRESENTATION: A 69-year-old Japanese man presented with pain and a polypoid mass on the lower left gingiva. He had received chemoradiotherapy for squamous cell carcinoma of the buccal mucosa 15 years prior to this consultation. In addition, he was treated for mandibular osteonecrosis 6 years after chemoradiotherapy without evidence of cancer recurrence. A biopsy revealed atypical spindle or pleomorphic cells scattered in the edematous and fibrin-rich stroma; however, no malignant squamous components were apparent. These atypical cells frequently contained neutrophils within their cytoplasm that formed cell-in-cell figures. Immunohistochemically, the atypical cells were negative for cytokeratins, epithelial membrane antigen, and E-cadherin, but positive for p63, vimentin, and p53. Although these findings suggested spindle cell squamous cell carcinoma, it was difficult to reach a definitive diagnosis. Based on a clinical diagnosis of a malignant tumor, the patient underwent a hemimandibulectomy. The surgically resected specimen had a typical spindle cell squamous cell carcinoma histology consisting of biphasic spindle cells and conventional squamous cell carcinoma components. Moreover, the surgical specimen also exhibited spindle tumor cells that frequently included neutrophils, around which intense staining for lysosomal-associated membrane protein 1 and cathepsin B was observed. This suggested that the cell-in-cell figures represent active neutrophil phagocytosis by tumor cells, and not emperipolesis. CONCLUSION: The presence of neutrophil phagocytosis may be a potent indicator of malignancy.

Variations in the venous supply of the floor of the oral cavity: Assessment of relative hemorrhage risk during surgery.

There is little anatomical evidence about the venous plexus in the floor of the oral cavity, although venous injury can elicit late postoperative bleeding after oral surgery and it is difficult to identify the exact location of such an injury. The aim of this study was to assess the relative risk for venous injury during surgery. We investigated the course patterns of the venous plexus in the floor of the oral cavity and analyzed their relationships to those of the arteries using 23 human cadavers (41 halves) in the anatomy course at Niigata University during 2016-2018. The venous plexus in the floor of the oral cavity comprised the perforating submental vein, the vena comitans of the hypoglossal nerve, the vena comitans of the submandibular duct, the vena comitans of the lingual nerve, the sublingual vein, and the deep lingual vein. Individual variations of this plexus include duplications or absences of some veins. There is a high incidence of a submental branch running above the mylohyoid or perforating submental artery in the sublingual fossa among individuals with the perforating submental vein piercing the mylohyoid muscle, whereas the sublingual artery has a high incidence there when there is no perforating submental vein. The course patterns of arteries in the floor of the oral cavity can be predicted by estimating the course patterns of the submental veins. The course patterns of the submental veins or veins associated with the nerves and submandibular duct need to be carefully considered during surgery.

The Occurrence Rate and Diameter of Arteries Traveling Near the Mandible and an Assessment of the Relative Hemorrhage Risk in Implant Surgery.

BACKGROUND: Bleeding in the floor of the mouth during implant surgery is attributed to arterial injuries in the sublingual space. PURPOSE: This study aimed to assess the relative hemorrhage risk during implant surgery. MATERIALS AND METHODS: We investigated the occurrence rate and diameter of submental and sublingual arteries with special reference to their relationship with the course patterns of these arteries using 26 human cadavers. RESULTS: Three types of arteries were distinguished: main duct (MD), mucoperiosteal branches (MB), and cortical branches (CB). The occurrence rate of MB and CB was significantly high at the central incisor region in the upper part of the mylohyoid muscle, whereas the diameter of the MB and CB was significantly smaller than the occurrence rate of MD at the incisor regions. The occurrence rate of MD in the submental artery was significantly higher at the lateral incisor, canine, and premolar regions in the lower parts, whereas the occurrence rate of MD was significantly lower at the second and third molars in the upper parts. CONCLUSION: The susceptibility of the submental artery to injury is suggested at the incisors, canine, premolars, and first molar regions during implant surgery.

Variation in arterial supply to the floor of the mouth and assessment of relative hemorrhage risk in implant surgery.

OBJECTIVES: Bleeding in the floor of the mouth during implant surgery is attributed to arterial injuries in the sublingual space: clinicians may injure the submental and sublingual arteries, which originate from the facial and lingual arteries, respectively. This study aimed to clarify the three-dimensional courses of submental and sublingual arteries and their topographic relation to the mandible. MATERIALS AND METHODS: During the gross anatomy course at the Faculty of Dentistry and Graduate School, Niigata University (2009-2011), we investigated the relationship between the courses of submental and sublingual arteries and their dividing patterns of the mylohyoid muscle, sublingual gland, and mandible using 27 human cadavers. RESULTS: The courses of submental and sublingual arteries were divided into four patterns: (1) the sublingual space was supplied by the sublingual artery (type I: 63%), (2) it was supplied by both the sublingual and submental arteries (type II: 5.6%), (3) it was supplied by the submental artery without the sublingual artery (type III: 29.6%), and (4) type III without the deep lingual artery originated from the lingual artery (type IV: 1.8%). In type II, III, and IV, the submental artery perforates the mylohyoid muscle or takes a roundabout route to travel near the surface of the mandible. The percentage occurrence of arteries traveling between the sublingual gland and mandible in type II, III, and IV (55%) is higher than that in type I (8.8%). CONCLUSION: Susceptibility of the submental artery in type II, III, and IV to injury during implant surgery is suggested.