Overview of the History of the Cranial Nerves: From Galen to the 21st Century.

Throughout history the description and classification of the cranial nerves has been linked to the development and characteristics of anatomy and the role that it played as a tool in providing rationality to medicine, together with social, cultural, religious, and philosophical factors. Anatomists were interested in the cranial nerves, but they disagreed on their number and their paths. We can divide the history of the cranial nerves into three different periods: the first, early or macroscopic period; the second or microscopic period; and the third period or ontogenesis and genoarchitecture. The main aim of this article is to show how the description and knowledge of the cranial nerves were developed in the course of these three periods, and to highlight the main changes produced and the factors related to these changes. We describe how the first period was mainly focused on establishing the definition, number and paths of the cranial nerves, through contributions ranging from Galen's studies in the second century to Sömmerring's Doctoral Dissertation in 1778 that described 12 cranial nerves for the first time. Then, the microscopic period was concentrated on the identification of the real nuclei of origin of the different cranial nerves located in the brain stem. Finally came the third period, or ontogenesis and genoarchitecture of the rhombecephalic and mesencephalic cranial nerve nuclei. Anat Rec, 302:381-393, 2019. © 2018 Wiley Periodicals, Inc.

Morphogenesis of the human laryngeal ventricles.

BACKGROUND: Two theories explain the origin of human laryngeal ventricles: (1) ventricles derive from the fifth pharyngeal pouches; (2) development independent from the pouches. METHODS: In all, there were 21 serially sectioned human embryos from stages 15 to 23, and 11 fetuses of 9 to 18 weeks. Computer-aided 3-dimentional reconstructions were made. RESULTS: The cranial part of the laryngeal sulcus and future vestibule expands from the pharyngeal floor between the third and fourth pharyngeal pouches during stages 15 and 16 (33-37 days). The primordia of the ventricles appeared at stage 18 (44 days) as 2 lateral swellings in the caudal end of the future vestibule, limited by the third pharyngeal pouches. Active epithelial expansion and subsequent canalization during late embryonic and early fetal periods finalizes their development. CONCLUSIONS: The laryngeal ventricles do not derive from the pharyngeal pouches but the median region of the pharyngeal floor between the third and fourth pharyngeal pouches and arches at the caudal end of the future vestibule.

Recurrent laryngeal nerve landmarks revisited.

BACKGROUND: The aim of this work was to evaluate, to prove their reliability, the different surgical landmarks previously proposed as a mean to locate the recurrent laryngeal nerve (RLN). METHODS: The necks of 143 (68 male and 76 female) human adult embalmed cadavers were examined. RLN origin and length and its relationship to different landmarks were recorded and results compared with those previously reported. Statistical comparisons were performed using the chi-square test (significance, p ≤ .05). RESULTS: Mostly, RLN is located anterior to the tracheoesophageal sulcus (41.6%), posterior to the inferior thyroid artery (35.8%), lateral to Berry's ligament (88.1%), below the inferior rim of the inferior constrictor muscle (90.4%), and entering the larynx before its terminal division (54.6%). CONCLUSIONS: The position of the RLN in relation to those structures classically considered as landmarks is highly variable. The most reliable relationships are those with Berry's ligament or the inferior constrictor muscle.

Potential structures that could be confused with a nonrecurrent inferior laryngeal nerve: an anatomic study.

OBJECTIVES: Study and detailed description of the large connections between the normally recurrent inferior laryngeal nerve (RILN) and the sympathetic trunk (ST) because these may be mistaken for a nonrecurrent inferior laryngeal nerve (NRILN). STUDY DESIGN: Morphologic study of adult human necks. METHODS: The necks of 144 human, adult, embalmed cadavers were examined (68 males, 76 females). They had been partially dissected by Cambridge preclinical medical students and then further dissected by the authors using magnification. The RILN, the ST, and their branches were identified and dissected. A total of 277 RILNs and STs (137 rights, 140 lefts) were observed. RESULTS: A communicating branch (CB) with a similar diameter to the RILN occurred between the ST and the RILN in 48 of the 277 (17.3%) dissections, 24 from the 137 (17.5%) right dissections, and 24 from the 140 (17%) left dissections. In 12 cases, the CB was bilateral. The CB arose from the superior cervical sympathetic ganglion in 3 of the 48 (6.25%) cases, from the middle ganglion in 10 (21%) cases, from the stellate ganglion in 3 (6.25%) cases, and from the ST in 32 (66.6%) cases. One (0.36%) NRILN associated with a right retro-esophageal subclavian artery (arteria lusoria) was found. CONCLUSIONS: 1) The CB between the RILN and the ST may have a diameter and course similar to an NRILN and may be confused with it. 2) The occurrence of the CB is greater than the occurrence referred to in previous studies. 3) The occurrence of the CB is similar by side and sex. 4) The CB may arise at different levels from the cervical ST and ganglia and end in the thyroid area. 5) Other neural elements may also be confused with an RILN, such as the cardiac nerves and the collateral branches from an NRILN to the trachea and esophagus.

Anatomic study of blood supply of the dorsum of the foot and ankle.

PURPOSE: This project was to study the different patterns of the anterior tibal and dorsalis pedis arteries in relation to the blood supply of the dorsum of the foot and ankle. METHODS: A reliable sample of 150 human embalmed cadavers was dissected. RESULTS: Four different patterns were identified. The dorsalis pedis artery was most frequently (287 cases, 95.7%) found to be the continuation of the anterior tibial artery distal to the ankle, and lay between the tendon of extensor hallucis and the first tendon of extensor digitorum longus. The other 13 cases (4.3%) showed 3 variant patterns of the anterior tibial-dorsalis pedis vascular axis: the anterior tibial artery took a more lateral course, passing in front of the lateral malleolus (6 cases, 2%); the perforating branch of the peroneal artery assumed the expected course of the dorsalis pedis artery (4 cases, 1.3%); the anterior tibal artery gave a lateral branch that replaced the perforating branch of the peroneal artery to supply the lateral aspect of the ankle (3 cases, 1%). CONCLUSION: Arterial variations of the anterior tibial-dorsalis pedis axis occurred in almost 5% of cases. CLINICAL RELEVANCE: An awareness of the existence of such variations is helpful during a preoperative assessment and could prevent injury during surgery.