Joe Iwanaga

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.

Clinical anatomy and surgical significance of the lingual foramina and their canals

The lingual foramina and canals can be categorized as median or lateral based on their relation to the midline of the mandible. Investigation of the mandibular lingual region is often done with gross anatomical dissections of cadavers, 2D panoramic radiographic imaging, CT, and cone beam CT (CBCT). While gross studies are the most reliable at qualifying canal contents and course, CBCT proved to be superior to other radiographic techniques for visualizing lingual foramina and canals. The submental and sublingual arteries, and their branches are found in the lingual vascular canals. There is tremendous variation between individuals in terms of the course of the lingual canals and their anastomosis with other vascular canals. Performing the dental implantation procedures in the anterior and posterior regions of the mandible can result in perforation of the lingual cortex, which could injure the arteries that lie within the lingual canal. If hemorrhage occurs, it could lead to life‐threatening upper airway obstruction. Pre‐surgical investigation to identify the diameter of the lingual foramina and canal as well as their distance from the alveolar process might be necessary to prevent hemorrhage for all patients. Clin. Anat. 30:194–204, 2017.

The filum terminale internum and externum: A comprehensive review

INTRODUCTION The filum terminale has oven been overlooked in the literature probably due to its small size and historical lack of research on its true morphology. However, this structures roll in the tethered cord syndrome has become more apparent. Therefore, the current comprehensive review seemed timely. METHODS Using standard search engines, the history, embryology, anatomy, pathology and surgery of the filum terminale were reviewed. CONCLUSIONS It is only recently that the true anatomy and pathological involvement of the filum terminale in the tethered cord syndrome have been elucidated.

Aortic Arch Origin of the Left Vertebral Artery: An Anatomical and Radiological Study with Significance for Avoiding Complications with Anterior Approaches to the Cervical Spine

Complications from anterior approaches to the cervical spine are uncommon with normal anatomy. However, variant anatomy might predispose one to an increased incidence of injury during such procedures. We hypothesized that left vertebral arteries that arise from the aortic arch instead of the subclavian artery might take a more medial path in their ascent making them more susceptible to iatrogenic injury. Fifty human adult cadavers were examined for left vertebral arteries having an aortic arch origin and these were dissected along their entire cervical course. Additionally, two radiological databases of CTA and arteriography procedures were retrospectively examined for cases of aberrant left vertebral artery origin from the aortic arch over a two‐year period. Two cadaveric specimens (4%) were found to have a left vertebral artery arising from the aortic arch. The retrospective radiological database analysis identified 13 cases (0.87%) of left vertebral artery origin from the aortic arch. Of all cases, vertebral arteries that arose from the aortic arch were much more likely to not only have a more medial course (especially their preforaminal segment) over the cervical vertebral bodies but also to enter a transverse foramen that was more cranially located than the normal C6 entrance of the vertebral artery. Spine surgeons who approach the anterior cervical spine should be aware that an aortic origin of the left vertebral artery is likely to be closer to the midline and less protected above the C6 vertebral level. Clin. Anat. 30:811–816, 2017.

Leonardo da Vinci (1452–1519) and his depictions of the human spine

IntroductionFew individuals in history have exerted so great an influence and made such extensive contributions to so many disciplines as Leonardo da Vinci. Da Vinci’s inquisitive, experimental mentality led him to many discoveries, such as spinal cord function and the proper anatomy of several organ systems. Respected not only as an artist but also as an anatomist, he made many significant contributions to the field.ConclusionsThis article explores da Vinci’s drawings, in relation to the anatomy of the human spine.

Translation of Hecker's 1922 “the occipital–atlanto–axial ligament system”: A study in comparative anatomy

In 1922, Paul Hecker, a French physician and Head of Anatomy at the Medical College of Strasbourg, published a sentinel thesis on the ligaments of the craniocervical junction based on a study of comparative anatomy. Unfortunately, this dissertation has been lost to history and until now, was unavailable in the English language. Herein, we present a translation of Heckers work with an update in its nomenclature, which with modern imaging capabilities of the craniocervical junction is germane and timely. Clin. Anat. 30:322–329, 2017.

Meningocele manqué: a comprehensive review of this enigmatic finding in occult spinal dysraphism

The term meningocele manqué (MM) was coined in 1972 to describe a broad range of surgical findings characterized by intradural bands tethering neural structures to the dorsal dura. Over the following decades, reports continued to lump intradural tethering bands associated with a variety of comorbidities under the umbrella term MM. In more recent years, disorders previously called MM have been identified as embryologically distinct and were reclassified. While this sectioning continues, there remains a set of intradural tethering disorders for which no better term than MM exists. Herein, we comprehensively review the literature surrounding MM, including embryological disorders, clinical, radiographic, and surgical presentation, as well as alternative classification methods and MM treatment.

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.

The influence of ancient Greek thought on fifteenth century anatomy: Galenic influence and Leonardo da Vinci

Leonardo da Vinci (1452–1519) can be called one of the earliest contributors to the history of anatomy and, by extension, the study of medicine. He may have even overshadowed Andreas Vesalius (1514–1564), the so-called founder of human anatomy, if his works had been published within his lifetime. While some of the best illustrations of their time, with our modern knowledge of anatomy, it is clear that many of da Vinci’s depictions of human anatomy are inaccurate. However, he also made significant discoveries in anatomy and remarkable predictions of facts he could not yet discover with the technology available to him. Additionally, da Vinci was largely influenced by Greek anatomists, as indicated from his ideas about anatomical structure. In this historical review, we describe da Vinci’s history, influences, and discoveries in anatomical research and his depictions and errors with regards to the musculoskeletal system, cardiovascular system, nervous system, and other organs.