Yoko Tabira

Accessory mental foramina and nerves: Application to periodontal, periapical, and implant surgery.

Recent studies investigating accessory mental foramina using developments in diagnostic imaging have primarily defined the morphology of the foramina; however, few studies have described the structures passing through them. Additional clinical knowledge of the foramina is therefore required for preoperative diagnosis prior to surgery, including implant, periodontal and periapical surgery. In this study, we investigated the accessory mental foramina and the associated nerves and arteries in donated cadaveric mandibles using anatomical and radiological observation methods. We examined 63 mandibles with overlying soft tissue by cone‐beam computed tomography and noted the existence of the accessory mental foramina. Mandibles with accessory mental foramina were subsequently analyzed. Additionally, the neurovascular bundles passing through these foramina were dissected using anatomical methods.The incidence of accessory mental foramina was 14.3%. The larger foramina tended to be located anteriorly or superiorly and proximal to the mental foramen, while the smaller foramina tended to be located posterosuperiorly and distal to the mental foramen. The mental foramen ipsilateral to the accessory mental foramen was smaller than the one contralateral to it. The comparatively distant and large accessory mental foramen included an artery.This study elucidated the relationship between accessory mental foramina and the associated nerves and arteries. We believe that the results will contribute to the clinical dentistry field. Clin. Anat. 29:493–501, 2016.

The clinical anatomy of accessory mental nerves and foramina

Since three‐dimensional computed tomography was developed, many researchers have described accessory mental foramina. The anatomical and radiological findings have been discussed, but details of accessory mental nerves (AMNs) have only been researched in a small number of anatomical and clinical cases. For this article, we reviewed the literature relating to accessory mental foramina (AMFs) and nerves to clarify aspects important for clinical situations. The review showed that the distribution pattern of the AMN can differ according to the position of the accessory mental foramen, and the reported incidence of AMFs differs among observation methods. A review of clinical cases also revealed that injury to large AMF can result in paresthesia. This investigation did not reveal all aspects of AMNs and AMFs, but will be useful for diagnosis and treatment by many dentists and oral and maxillofacial surgeons. Clin. Anat. 28:848–856, 2015.

Influence of a fabella in the gastrocnemius muscle on the common fibular nerve in Japanese subjects

The fabella is a sesamoid bone located in the proximal tendon of the gastrocnemius muscle. In rare cases, its presence may lead to a variety of clinical problems, including fabella syndrome and common fibular (CF) nerve palsy. The purpose of this study was to analyze the morphology of the fabella and CF nerve and discuss the influence of any existing fabellae on the size of the CF nerve. The morphology of the fabella and CF nerve in the popliteal region of the lateral head of the gastrocnemius muscle was investigated in 102 knees of 51 Japanese cadavers. The maximum circumference of the thigh, knee, and calf and the frequency, position, and size of the fabella were measured. In addition, the CF nerve width and thickness were measured proximal to the fabellar region and again as the CF nerve passed posterior, lateral, or medial to the region. A fabella was observed in 70 knees (68.6%). The CF nerve adjacent to the fabella was significantly wider and thinner than in the region proximal to the fabella (P < 0.001). In cases in which a bony fabella was present, there was a significant relationship between the thickness of the CF nerve and the circumference of the thigh and knee. The following factors were observed to contribute to the presence of a fabella causing alterations in the size of the CF nerve: a bony fabella, a CF nerve path posterior or lateral to the fabella, and subjects with a thin physique and bony fabella. Clin. Anat. 26:893–902, 2013.

A rare case of dual origin of the left vertebral artery without convergence

A case of dual origin of the left vertebral artery was encountered in a dissection course for medical students in 2014. Two vertebral arteries were observed on the left side. One arose from the aortic arch between the origin of the left common carotid artery and the left subclavian artery, entered the transverse foramen of the 4th cervical vertebra, and coursed upward into the transverse foramen. The other arose from the left subclavian artery as expected, divided into two branches anterior to the cervical vertebrae, and entered the transverse foramina of the 6th and 7th cervical vertebrae. Both branches flowed into the anterior spinal artery. Moreover, as seen in other anomalies, 3 arterial fenestrations were observed in the cranial arteries. This case is extremely unique with respect to the following points: the 2 ipsilateral vertebral arteries did not combine to form 1 vertebral artery, the vertebral artery of subclavian artery origin entered the transverse foramen of the 7th cervical vertebra, and 3 fenestrations were observed in the intracranial arteries. This is a very suggestive case for neurosurgeons and radiologists who perform treatments involving the vertebral artery.

Communicating branches between lingual and hypoglossal nerve: observation using Sihler’s staining technique

PurposeMany dental procedures are at risk of injuring the lingual nerve. We performed this study to better elucidate the microanatomy that exists between the ipsilateral lingual and hypoglossal nerves so that iatrogenic injury can be avoided.MethodsAdult human cadaveric tongues (ten sides) underwent Sihler’s staining to identify the microanatomy between the lingual and hypoglossal nerves.ResultsThe lingual nerve entered the middle part of the anterior two-thirds of the tongue from its lateral side and divided into two to four thick branches. These branches were then disseminated to the anterior, middle, and posterior parts of the anterior two-thirds of the tongue via 7–14 thin nerve bundles as terminal branches. The hypoglossal nerve entered the tongue at the posterior border of its anterior two-thirds and traveled forward to the apex of the tongue on all sides. All specimens were found to have communicating branches between the lingual and hypoglossal nerves at its anterior, middle, and posterior thirds.ConclusionsOur results indicate that the ipsilateral lingual and hypoglossal nerves constantly have three connections on each side between them. This knowledge might aid the dentist in minimizing iatrogenic nerve injury.

Tortuous Common Carotid Artery: A Report of Four Cases Observed in Cadaveric Dissections

A tortuous common carotid artery poses a high risk of injury during tracheotomy. Preoperative diagnosis is therefore important to avoid serious complications. We found four cases of tortuous common carotid artery during an anatomical dissection course for students. The first case was a 91-year-old woman who had bilateral tortuous common carotid arteries without arteriosclerosis. Case 2 was a 78-year-old woman who had bilateral tortuous common carotid arteries without arteriosclerosis. Case 3 was an 86-year-old woman who died from bladder cancer and who also had a right tortuous common carotid artery without arteriosclerosis. Case 4 was an 89-year-old woman who had bilateral tortuous common carotid arteries and a tortuous brachiocephalic artery with severe arteriosclerosis. Case 4 was also examined using computed tomography to evaluate the arteriosclerosis. Computed tomography revealed severe calcification of the vascular wall, which was confirmed in the aortic arch and origins of its branches. In all four cases, the tortuosity was located below the level of the thyroid gland. Based on prior study results indicating that fusion between the carotid sheath and visceral fascia was often evident at the level of the thyroid gland, we speculated that the major region in which tortuosity occurs is at the same level or inferior to the level of the thyroid gland.

A Rare Case of an Artery Passing through the Median Perforating Canal of the Mandible

Along with the popularization of dental implant surgery, there has been considerable research on the lingual foramen using cone-beam computed tomography. Anatomical research has also revealed that the arteries entering the lingual foramina are branches of the submental and sublingual arteries. There have been no reports, however, of the submental or sublingual artery entering the mandible from the lingual foramen, perforating it, and then distributing to the inferior labial region. A 69-year-old man who donated his body to our department in 2015 was dissected. The mandible with overlying soft tissue of the mental region was resected and examined with microcomputed tomography, which showed that the canal perforated from the lingual foramen to the midline of the labial cortical plate. The canal was thus named the median perforating canal. To the best of our knowledge, there have been no other reports of a perforating artery of the mandible, so this case is thought to be rare. Hence, the existence of perforating arteries, such as in the present case, should be taken into consideration in preoperative diagnoses such as for dental implant surgery. Thus, the fusion of anatomical and radiological study is useful and necessary to understand surgical anatomy.

Anatomical Research of the Three-dimensional Route of the Thoracodorsal Nerve, Artery, and Veins in Latissimus Dorsi Muscle.

Background: The latissimus dorsi (LD) muscle flap has been widely used in facial reanimation surgery. However, there are no standards to what degree the muscle flap may be safely thinned because the three-dimensional positional relationship of thoracodorsal artery, vein, and nerve inside the LD muscle is poorly understood. Methods: From 18 formalin-fixed cadavers, we made 36 transparent specimens of LD muscles using a newly developed decoloration technique. In 26 specimens, nerve staining (Sihler’s staining method) and silicone rubber (Microfil) injection to the thoracodorsal artery were performed, and the relationship of the artery and the vein was examined in 10 specimens. Results: The thoracodorsal artery and vein always ran parallel in a deeper layer compared to the nerve. The thoracodorsal nerve constantly existed in a deeper layer than half (50%) of the muscle in the range of use of the muscle flap in facial reanimation surgery. Conclusions: The thoracodorsal nerves ran in a shallower layer, and the depth to the nerve in the muscle flap in actual facial reanimation surgery is safe enough to avoid damage to the nerves. The LD muscle may be thinned to half its original thickness safely.

An anatomical study of the transversus nuchae muscle: Application to Better Understanding Occipital Neuralgia

The transversus nuchae muscle appears inconsistently in the occipital region. It has gained attention as one of the muscles composing the superficial musculoaponeurotic system (SMAS). The purpose of this study was to clarify its detailed anatomical features. We examined 124 sides of 62 cadavers. The transversus nuchae muscle was identified when present and examined after it had been completely exposed. We also examined its relationship to the occipital cutaneous nerves.The transversus nuchae muscle was detected in 40 sides (40/124, 32.2%) of 26 cadavers; it was present bilaterally in 14 and unilaterally in 12. It originated from the external occipital protuberance; 43% of the observed muscles inserted around the mastoid process, and 58% curved upward around the mastoid process and became the uppermost bundle of the platysma. In one case, an additional bundle originated from the lower posterior border of the sternocleidomastoid muscle and coursed obliquely upward along with platysma. Ninety percent of the muscles ran below the sling through which the greater occipital nerve passed; 65% of the lesser occipital nerves ran deep to the muscle, and 55% of the great auricular nerves ran superficial to it. Our observations clarify the unique anatomical features of the transversus nuchae muscle. We found that it occurs at a rate similar to that described in previous reports, but its arrangement is variable. Further investigations will be performed to clarify its innervation and other anatomical features. Clin. Anat. 30:32–38, 2017.

A Novel Method for Observation of the Mandibular Foramen: Application to a Better Understanding of Dental Anatomy

Cone‐beam computed tomography gives us much useful morphological information about the mandibular bone. Many studies of the mandible include findings from this technique. However, there have been no endoscopic studies of the mandible. Sixteen sides of eight dry mandibles resected from cadavers (age range 38–83 years) were examined by endoscopy. The head of the endoscope was 2.0 mm in diameter. We examined the mandibular foramen, lingula, mylohyoid groove, and mandibular canal. The mylohyoid grooves showed variations such as double grooves and canals. The mandibular lingula was located superior or medial to the the mandibular foramen. In a single case, the medial wall inside the mandibular canal showed a porous surface. The retromolar canal was observed in three sides. None of the images in the present study have been seen in other studies. Observation of the retromolar canal from the mandibular canal in particular can help dental students as well as oral and maxillofacial surgeons to understand its morphology. Anat Rec, 2017.