Koichi Watanabe

The intracranial arachnoid mater: A comprehensive review of its history, anatomy, imaging, and pathology

IntroductionThe arachnoid mater is a delicate and avascular layer that lies in direct contact with the dura and is separated from the pia mater by the cerebrospinal fluid-filled subarachnoid space. The subarachnoid space is divided into cisterns named according to surrounding brain structures.MethodsThe medical literature on this meningeal layer was reviewed in regard to historical aspects, etymology, embryology, histology, and anatomy with special emphasis on the arachnoid cisterns. Cerebrospinal fluid dynamics are discussed along with a section devoted to arachnoid cysts.ConclusionKnowledge on the arachnoid mater and cerebrospinal fluid dynamics has evolved over time and is of great significance to the neurosurgeon in clinical practice.

Neuroanatomy of the female abdominopelvic region: A review with application to pelvic pain syndromes

Pelvic pain can be a life altering disease. Multiple pathologies can affect this region resulting in neurologic issues. Therefore, a thorough understanding of the nerve supply to this region is important for the clinician who treats such patients. The current review outlines the anatomy of the nervous system of the abdominopelvic region with special attention to this anatomy in the female. Clin. Anat. 26:66–76, 2013.

L5 spondylolysis/spondylolisthesis: a comprehensive review with an anatomic focus

IntroductionSpondylolysis is most commonly observed in the lumbar spine, particularly L5, and is associated with spondylolisthesis, or anterior “slippage” of a vertebra in relation to an adjacent vertebra. Isthmic spondylolisthesis is the result of a pars interarticularis defect and will be the only type of spondylolisthesis addressed in this review.ConclusionsSpondylolysis and spondylolisthesis represent a relatively common cause of low back pain, especially in young athletes, and a less common cause of neurologic compromise. When discovered in a symptomatic patient with corroborating imaging findings, early intervention provides an excellent prognosis. Herein, we review the anatomy and pathology of spondylosis and spondylolisthesis of the L5 vertebra.

The intramuscular course of the greater occipital nerve: Novel findings with potential implications for operative interventions and occipital neuralgia

Background: A better understanding of the etiologies of occipital neuralgia would help the clinician treat patients with this debilitating condition. Since few studies have examined the muscular course of the greater occipital nerve (GON), this study was performed. Methods: Thirty adult cadaveric sides underwent dissection of the posterior occiput with special attention to the intramuscular course of the GON. Nerves were typed based on their muscular course. Results: The GON traveled through the trapezius (type I; n = 5, 16.7%) or its aponeurosis (type II; n = 15, 83.3%) to become subcutaneous. Variations in the subtrapezius muscular course were found in 10 (33%) sides. In two (6.7%) sides, the GON traveled through the lower edge of the inferior capitis oblique muscle (subtype a). On five (16.7%) sides, the GON coursed through a tendinous band of the semispinalis capitis, not through its muscular fibers (subtype b). On three (10%) sides the GON bypassed the semispinalis capitis muscle to travel between its most medial fibers and the nuchal ligament (subtype c). For subtypes, eight were type II courses (through the aponeurosis of the trapezius), and two were type I courses (through the trapezius muscle). The authors identified two type IIa courses, four type IIb courses, and two type IIc courses. Type I courses included one type Ib and one type Ic courses. Conclusions: Variations in the muscular course of the GON were common. Future studies correlating these findings with the anatomy in patients with occipital neuralgia may elucidate nerve courses vulnerable to nerve compression. This enhanced classification scheme describes the morphology in this region and allows more specific communications about GON variations.

The pia mater: a comprehensive review of literature

IntroductionThe pia mater has received less attention in the literature compared to the dura and arachnoid maters. However, its presence as a direct covering of the nervous system and direct relation to the blood vessels gives it a special importance in neurosurgery.MethodA comprehensive review of the literature was conducted to study all that we could find relating to the pia mater, including history, macro- and microanatomy, embryology, and a full description of the related structures.ConclusionThe pia mater has an important anatomic position, rich history, complicated histology and embryology, and a significant contribution to a number of other structures that may stabilize and protect the nervous system.

Histologic confirmation of neuronal cell bodies along the spinal accessory nerve

Abstract Introduction. Most sources conclude that the spinal accessory nerve (SAN) is a purely motor nerve. There are some reports that suggest a sensory component, although the exact nature of such sensory fibers has yet to be elucidated. With such discrepancies in the literature and with well-established pain syndromes of unknown etiology following SAN injury, the authors performed the present study to better clarify this anatomy. Materials and methods. The entire accessory nerve was harvested from 10 adult cadavers. Samples were then submitted for immunohistochemical analyses. Results. Occasional microganglia cells were identified along the SAN in all specimens. These ganglia were most numerous along the intracranial segment of the SAN, but none was found along the cranial rootlets of the accessory nerve. Conclusions. Neuronal cell bodies were identified along the course of the SAN in human cadavers. Although the function is not certain, such cells have been found in other animals to be nocioceptive in nature. Pending further study, these cells may be found to be involved in enigmatic pain syndromes thought to arise in the sternocleidomastoid and trapezius muscles.

Anatomy of the inferior petro-occipital vein and its relation to the base of the skull: application to surgical and endovascular procedures of the skull base.

Although the inferior petro‐occipital vein has been recently used for vascular access to the cavernous sinus, few detailed descriptions of its anatomy are in the literature. We aimed to investigate the morphology and relationships of this vessel. Twelve latex‐injected cadaveric heads (24 sides) were dissected to identify the inferior petro‐occipital vein and anatomic details documented. The petro‐occipital vein was identified on 83.3% of sides. Generally this vein united the internal carotid venous plexus to the superior jugular bulb. However, on 10% of sides, the anterior part of this vein communicated directly with the cavernous sinus, and on 15%, the posterior vein drained into the inferior petrosal sinus at its termination into the superior jugular bulb. The petro‐occipital vein was separated from the overlying inferior petrosal sinus by a thin plate of bone. On 40% of sides, small venous connections were found between these two venous structures. The vein was usually larger if a nondominant transverse sinus was present. The overlying inferior petrosal sinus was smaller in diameter when an underlying inferior petro‐occipital vein was present. On 20% of sides, the posterior aspect of the vein communicated with the hypoglossal canal veins. On three sides, diploic veins from the clivus drained into the inferior petro‐occipital vein. The inferior petro‐occipital vein is present in most humans. This primarily extracranial vessel communicates with intracranial venous sinuses and should be considered an emissary vein. Knowledge of this vessels exact anatomy may be useful to cranial base surgeons and endovascular specialists. Clin. Anat. 27:698–701, 2014.

Formaldehyde exposure and its effects during pregnancy: Recommendations for laboratory attendance based on available data.

Formalin is commonly used in fixation of cadaveric specimens. Exposure to formaldehyde, a component of formalin and a known carcinogen, during gross anatomy laboratory dissection is a continuing concern for pregnant students and instructors. Since there is little literature on this specific topic, the current review was compiled in the hope of offering recommendations to pregnant students and instructors who are engaged in human anatomical dissection where formalin is used. Relevant articles were obtained through searches of PubMed and Google Scholar for the terms “formaldehyde,” “pregnant,” “formalin,” and “exposure.” A literature search was conducted for chemical information and articles about exposure as issued by government regulatory agencies and chemical companies that produce formaldehyde. This led to the compilation of 29 articles each of which included references to previous, relevant, human research. The reviewed literature contains data strongly suggesting that pregnancy can be affected by formaldehyde exposure. Therefore, on the basis our analysis, female students who might be pregnant should avoid formaldehyde exposure, including that in a gross anatomy laboratory. Instructors should find other means of ensuring anatomical competence for these students. Clin. Anat. 28:972–979, 2015.

Benjamin Hobson (1816-1873)

Benjamin Hobson was a British missionary and physician who lived in China for twenty years. He founded multiple hospitals in Southern China and used his knowledge of Western medicine to educate Chinese doctors. He wrote several medical textbooks in Chinese of which the first was the A New Theory of the Body (1851). The illustrations from his book were renditions and originals from William Cheseldens Anatomical Tables (1730) and Osteographia (1733).The Japanese version of Hobsons work appeared in Japan during the bakumatsu period (1853–1867), when Japan ended its isolationist foreign policy and began opening itself to the West. During this time, many books from Europe were translated into Chinese to then find their way into Japan. The Chinese anatomy textbook by Hobson (Quanti Xinlun) was instrumental in introducing Western anatomic knowledge to the Chinese and thereby catalyzing a significant change in the practice of medicine in China. A Japanese translation (Zen Tai Shin Ron) of this text published in the 19th century is reviewed. Clin. Anat. 27:154–161, 2014.

The history of the surgical repair of spina bifida

IntroductionThe history of surgical spina bifida repair has seen many successes and failures. Many early surgeons attempted treatment of open spina bifida defects before a clear understanding of the disease process or pathology had been discovered.ConclusionsThe attempts, while often fruitless, served to better our understanding of the disease and represent stepping-stones to the treatment we successfully use today. The present paper reviews the history of the surgical treatment of myelomeningoceles.