Jugular bulb anatomical variations and pneumatization patterns: a comprehensive CBCT analysis.

PURPOSE: This study aims to assess the anatomical possibilities of the jugular bulb (JB). METHODS: Fifty archived CBCT scans were analyzed. RESULTS: The average distance between the internal acoustic canal (IAC) and the JB was 7.97 mm on both sides (Right: SD = 2.56 mm, range 3.16-13.3 mm; Left: SD = 2.5 mm, range 2.9-13.6 mm). JB walls' pneumatization was classified into eight patterns. Deep petrosal cells (DPCs) prevailed in the lateral wall of the JB. The absence of pneumatization (NP) was commonly found on the left side. The presence of infralabyrinthine and hypotympanic cells varied. Less common types included accessory occipital cells (AOCs), posteromedial tracts (PMTs), and basi-occipital cells (BOCs), which determined a consistent variation of the lateral wall pneumatization patterns. Pneumatization of the medial wall was not observed in 50 right sides and 49 left sides. The inferior wall analysis revealed symmetry in AOC distribution and a predominant occurrence of NP. Cases with hypotympanum (HT) in the lateral wall showed a statistically significant IAC-JB distance increase by an average of 4.67 mm compared to NPs. Specific pneumatizations, particularly HT on the lateral side, have a significant effect on the IAC-JB distance, showing a clear pattern of increasing distance from DPC to NP and then to HT. A significant distance increase in HT pneumatization was noted. There were also recorded instances of JB hypoplasia and hyperplasia, JB diverticula, dehiscent JBs, and high JBs. CONCLUSION: This study establishes a novel classification of JB pneumatizations to aid in the understanding of the temporal bone anatomy.

The Anterolateral Approach, Revisited for Benign Jugular Foramen Tumors With Predominant Extracranial Extension: Microsurgical Anatomy and Case Series (SevEN-012).

BACKGROUND AND OBJECTIVES: The anterolateral approach (ALA) enables access to the mid and lower clivus, jugular foramen (JF), craniocervical junction, and cervical spine with added anterior and lateral exposure than the extreme lateral and endoscopic endonasal approach, respectively. We describe the microsurgical anatomy of ALA with cadaveric specimens and report our clinical experience for benign JF tumors with predominant extracranial extension. METHODS: A stepwise and detailed microsurgical neurovascular anatomy of ALA was explored with cadaveric specimens. Then, the clinical results of 7 consecutive patients who underwent ALA for benign JF tumors with predominant extracranial extension were analyzed. RESULTS: A hockey stick skin incision is made along the superior nuchal line to the anterior edge of the sternocleidomastoid muscle (SCM). ALA involves layer-by-layer muscle dissection of SCM, splenius capitis, digastric, longissimus capitis, and superior oblique muscles. The accessory nerve runs beneath SCM and is found at the posterior edge of the digastric muscle. The internal jugular vein (IJV) is lateral to and at the level of the accessory nerve. The occipital artery passes over the longissimus capitis muscle and IJV and into the external carotid artery, which is lateral and superficial to IJV. The internal carotid artery (ICA) is more medial and deeper than external carotid artery and is in the carotid sheath with the vagus nerve and IJV. The hypoglossal and vagus nerves run along the lateral and medial side of ICA, respectively. Prehigh cervical carotid, prejugular, and retrojugular surgical corridors allow deep and extracranial access around JF. In the case series, gross and near-total resections were achieved in 6 (85.7%) patients without newly developed cranial nerve deficits. CONCLUSION: ALA is a traditional and invaluable neurosurgical approach for benign JF tumors with predominant extracranial extension. The anatomic knowledge of ALA increases competency in adding anterior and lateral exposure of extracranial JF.

Anatomy of small canals around the jugular foramen: Special reference to Jacobson's and Arnold's nerves.

The jugular foramen harbors anatomically complex bony, venous and neural structures. It is closely associated with small canals including the mastoid, tympanic, and cochlear canaliculi, and the stylomastoid foramen. The minute intraosseous branches of Arnold's and Jacobson's nerves (<1 mm in length) remain difficult to study with current imaging techniques, and cadaveric dissection is the most reliable approach. Our aim was to examine the variations of Jacobson's and Arnold's canaliculi and nerves and to provide detailed cadaveric graphics. To reveal the anatomical structures of small canals around the jugular foramen, 25 sides of dry skulls and 14 sides of cadaveric heads were examined. Intraosseous branches varied more in Arnold's nerve than Jacobson's nerve. In our cadaveric dissection, all specimens formed a single canal for Jacobson's nerve connecting the jugular foramen to the tympanic cavity. The intraosseous course of Arnold's nerve varied in its communication with the facial nerve. A descending branch crossing the facial nerve was identified in five of 14 sides, an ascending branch in 13. In two specimens, an ascending branch clearly reached the base of the stapedius muscle. Classical anatomical studies of cadavers remain a supplementary tool for analyzing these tiny structures. The present study confirms Gray's findings of 1913. Variations of these nerves could be even more complex than previously reported. Our study provides additional information regarding the anatomy of Jacobson's and Arnold's nerves.

Endoscopic Endonasal Approach to the Ventral-Medial Portion of Posterior Paramedian Skull Base: A Morphometric Perspective of Surgical and Radiologic Anatomy.

OBJECTIVE: This study aims to provide morphometric analysis of endoscopic endonasal approach (EEA) to the ventral-medial portion of posterior paramedian skull base. Furthermore, it aims to investigate the surgical exposure obtained through EEA with and without eustachian tube (ET) removal, emphasizing the role of contralateral nostril (CN) access. METHODS: Five fresh adult head specimens were prepared for dissection. A predissection and a postdissection computed tomography study was performed. A surgically oriented classification into 4 regions was used: 1) tubercular region; 2) occipital condyle region; 3) parapharyngeal space (PPhS) region; and 4) jugular foramen (JF) region. The Student t-test was used to compare angulations and measures of EEA with access from the ipsilateral and CN, respectively, with and without ET removal. RESULTS: EEA to the ventral-medial portion of posterior paramedian skull base encompasses 2 medial trajectories (transtubercular and transcondylar) and 2 lateral pathways to the PPhS and JF. The CN access, without removal of the ET, allows a complete exposure of the petrous and intrajugular portion of the JF and superior PPhS without exposition of the parapharyngeal segment of internal carotid artery. The ipsilateral nostril approach with ET removal allows to obtain a wider exposure, reaching the medial sigmoid part of the JF. No significant differences exist in regard to transtubercular and transcondylar approaches. CONCLUSIONS: This study suggests that EEA to posterior paramedian skull base allows the realization of a corridor directed to the jugular tubercle, occipital condyle, medial PPhS, and ventral-medial JF. The CN approach with ET preservation can expose the petrous and intrajugular parts of the JF and PPhS. Case series are needed to demonstrate benefits and drawbacks of these approaches.

Presence of complete or incomplete septa in human jugular foramens / Presencia de septos completos o incompletos en forámenes yugulares humanos

SUMMARY: The objective of this study was to determine the occurrence of anatomical variants in the exocranial surface of the jugular foramen, specifically, the presence of single or double and complete or incomplete septation. A cross-sectional anatomical study was performed using 96 Brazilian dry human skulls (53 male and 43 female). One examiner determined the number (single or double) and type (i.e. complete or incomplete) of osseous septation at the outer surface of jugular foramens. Data went through statistical analysis on GraphPad Prism 6.01. Our results shown that Male individuals where more likely to present normal jugular foramens (male = 71.69%, female = 34.88%; p = 0.003). However, one incomplete septation occurred more often on the right side of female individuals (1 incomplete septation, male = 16.98%; 1 incomplete septation, female = 34.88%; p = 0.044). Similarly, one complete septation (i.e. the presence of two fully divided jugular compartments) also occurred more often on the right side of female individuals (1 complete septation, male = 9.43%; 1 complete septation, female = 25.58%; p = 0.038). Anatomical variants of the jugular foramen regarding single or double complete or incomplete septations were more likely to be found on the right side of female individuals, whose also presented a higher rate of jugular foramens with any type of septation than regular non-altered jugular foramens.

RESUMEN: El objetivo de la presente investigación fue determinar la presencia de variaciones anatómicas en la superficie exocraneal del foramen yugular, especificamente, la presencia de septos únicos o dobles, completos o incompletos. El estudio fue realizado en 96 cráneos secos (53 masculinos y 43 femeninos) de indivíduos Brasileños. Se determinaron septos óseos completos o incompletos y número de ellos. Los resultados obtenidos fueron tratados estadísticamente con el programa GraphPad Prism 6.01. Los sujetos de sexo masculino fueron más propensos a presentar forámenes yugulares normales (sexo masculino: 71,69%; sexo femenino: 34,88%, p= 0,003). Sin embargo, se observaron septos incompletos con mayor frecuencia en el lado derecho y en el sexo femenino (sexo masculino: 16,98%; sexo femenino: 34,88%, p=0,044). Adicionalmente, una septación completa (presencia de dos compartimientos yugulares, divididos completamente), se presentaron más frecuentemente en el lado derecho de indivíduos femeninos (sexo masculino: 9,43%; sexo femenino: 25,58%, p= 0,038). Las variantes anatómicas del foramen yugular, en relación a septos simples o dobles, completos o incompletos, se encontraron con mayor frecuencia en el lado derecho de las mujeres, las que presentaron un alto rango de forámenes yugulares con algún tipo de septos respecto a los forámenes yugulares regulares no alterados.

Does measurement of the jugular foramen diameter on MRI help to differentiate transverse sinus thrombosis from unilateral transverse sinus hypoplasia?

BACKGROUND AND PURPOSE: The transverse sinus (TS) is a frequent location of cerebral venous thrombosis. However, unilateral TS hypoplasia is a frequent variation and radiological imaging pitfall in the diagnosis because it may mimic unilateral TS thrombosis. The purpose of this study is to find a cutoff value for bilateral jugular foramen (JF) diameter ratios on magnetic resonance imaging (MRI) for differentiating TS thrombosis from TS hypoplasia. MATERIALS AND METHODS: We retrospectively reviewed magnetic resonance venography results for 174 patients with reduced unilateral TS caliber resulting from either unilateral thrombosis (80 patients) or unilateral hypoplasia (94 patients). We calculated the ratio by proportioning the diameter of the JF ipsilateral to the TS with caliber reduction to the diameter of the contralateral JF. The Mann-Whitney U test was used to compare the ratios between thrombosis and hypoplasia groups, and the cutoff value was calculated by receiver-operating characteristic curve analysis. RESULTS: The ratio of bilateral JF diameters was lower in patients with hypoplasia than those with thrombosis (P < .01). The cutoff value to determine the diagnosis of TS hypoplasia with maximum accuracy was 0.638, with a sensitivity of 91.3% and specificity of 64.9%. CONCLUSION: In equivocal cases, calculating the cutoff value by proportioning the diameter of JF ipsilateral to the TS with caliber reduction to the contralateral JF seems to be an efficient, quick, and straightforward method and valuable aid to differentiate TS thrombosis from TS hypoplasia.

Intraforaminal Dural Septations of the Jugular Foramen: A Cadaveric Study.

OBJECTIVE: The aim of this study was to define the types, prevalences, and diameters of dural septations (DSs) on the inner surface of the jugular foramen (JF) and to describe the distances between the JF, the glossopharyngeal nerve (cranial nerve [CN] IX), vagus nerve (CN X), and accessory nerve (CN XI), the internal acoustic meatus, and nearby surgical landmarks on cadaveric heads. METHODS: Seventeen adult (9 men and 8 women) formalin-fixed cadaveric heads were used to analyze the types and prevalence of DS bilaterally. Diameters and distances between the DS and the adjacent CNs (CN IX-XI) were measured by digital microcaliper. The multiple t test (SPSS version 25) was used to analyze the comparison between both sides via diameters, numbers, distance, length, and thickness of DS. RESULTS: The most frequent type of DS was type I (62.5%, right; 56.3%, left), followed by type II (18.8%, right; 25%, left), type III (12.5%, right; 6.3%, left), and type IV (6.3%, right; 12.5%, left). The mean diameter of the septum was 0.6-1 mm, and the mean length of the dural septa was 4.01 mm (right) and (3.83 mm) left. The difference in the length and thickness of the DS between the genders was statistically significant on both sides (P < 0.05). The DS-CN X and DS-JF distances of women were greater than those of men on the right side (P < 0.05). CONCLUSIONS: The significant differences between dural septum types on the 2 sides of the body may indicate asymmetric location or a variant emerging site of CNs in the same individual.

Quantitative Analysis of the Vascular and Neural Compartments of the Jugular Foramen in Dry Skulls.

AIM: To compare the right and left sides and the endo?exocranial orifices of the jugular foramen (JF) considering the vascular compartment (VC) and the neural compartment (NC). MATERIAL AND METHODS: A total of 20 human dry skulls belonging to the inventory of Medical Faculty, Department of Anatomy, were included in this study. Numerical values were obtained using direct anatomical and also computed tomography measurements. RESULTS: The endocranial and exocranial VC occupied wider areas on the right side than on the left side (p < 0.05). However, there was no statistically significant difference between the surface area of the endocranial and exocranial NC in terms of the sides (p > 0.05). The length of the endocranial VC was greater on the right than on the left side. The right exocranial VC was wider than the left exocranial VC. However, the widths and lengths of the endocranial and exocranial NC showed no statistically significant difference between the sides (p > 0.05). CONCLUSION: The right-sided dominance of JF observed in this study was attributed to the length of endocranial VC and the width of exocranial VC.

Anatomical study of jugular foramen in the neck / Estudo anatômico do forame jugular no pescoço

Abstract Introduction The anatomical complexity of the jugular foramen makes surgical procedures in this region delicate and difficult. Due to the advances in surgical techniques, approaches to the jugular foramen became more frequent, requiring improvement of the knowledge of this region anatomy. Objective To study the anatomy of the jugular foramen, internal jugular vein and glossopharyngeal, vagus and accessory nerves, and to identify the anatomical relationships among these structures in the jugular foramen region and lateral-pharyngeal space. Methods A total of 60 sides of 30 non-embalmed cadavers were examined few hours after death. The diameters of the jugular foramen and its anatomical relationships were analyzed. Results The diameters of the jugular foramen and internal jugular vein were greater on the right side in most studied specimens. The inferior petrosal sinus ended in the internal jugular vein up to 40 mm below the jugular foramen; in 5% of cases. The glossopharyngeal nerve exhibited an intimate anatomical relationship with the styloglossus muscle after exiting the skull, and the vagal nerve had a similar relationship with the hypoglossal nerve. The accessory nerve passed around the internal jugular vein via its anterior wall in 71.7% of cadavers. Conclusion Anatomical variations were found in the dimensions of the jugular foramen and the internal jugular vein, which were larger in size on the right side of most studied bodies; variations also occurred in the trajectory and anatomical relationships of the nerves. The petrosal sinus can join the internal jugular vein below the foramen.

Resumo Introdução A complexidade anatômica do forame jugular torna a realização de procedimentos cirúrgicos nessa região delicada e difícil. Devido aos avanços obtidos nas técnicas cirúrgicas, as abordagens do forame jugular têm sido feitas com maior frequência, o que requer uma melhoria correspondente no conhecimento de sua anatomia. Objetivo Estudar a anatomia do forame jugular, da veia jugular interna e dos nervos glossofaríngeo, vago e acessório, assim como as relações anatômicas entre estas estruturas na região do forame jugular e no espaço parafaríngeo. Método Foram examinados 60 lados de 30 cadáveres frescos algumas horas após a morte. Os diâmetros e suas relações anatômicas foram analisados. Resultados Os diâmetros do forame jugular e da veia jugular interna foram maiores no lado direito na maioria dos espécimes estudados. O seio petroso inferior terminava na veia jugular interna até 40 mm abaixo do forame jugular, em 5% dos casos. O nervo glossofaríngeo exibiu uma relação íntima anatômica com o músculo estiloglosso após a sua saída do crânio e o nervo vago exibiu uma relação semelhante com o nervo hipoglosso. O nervo acessório passou em torno da veia jugular interna via sua parede anterior em 71,7% dos cadáveres. Conclusão Foram encontradas variações anatômicas nas dimensões do forame jugular e da veia jugular interna, que apresentaram tamanhos maiores à direita na maioria dos espécimes estudados; variações também ocorreram na trajetória e nas relações anatômicas dos nervos. O seio petroso pode se unir à veia jugular interna abaixo do forame.

Compartmental Subdivisions of the Jugular Foramen: A Review of the Current Models.

BACKGROUND: At present, no consensus has been reached on the compartmental subdivision of the jugular foramen (JF), which can complicate surgical planning in this area and hinder understanding of foraminal tumor growth patterns. The extradural neural axis compartment (EDNAC) might aid in producing a standardized model in the future. In the present review, we have summarized the models of JF compartmentalization and analyzed how sound they are anatomically. METHODS: The present narrative review identified the key studies and supporting reports that had discussed, referenced, or first presented models of JF compartmentalization. RESULTS: Three intraforaminal components serve as the basis for JF compartmentalization: the fibro-osseous bridge, neurovascular contents, and EDNAC. A total of 4 models have been proposed to date. These include the 2-part (bipartite) models by Hovelacque (1934) and Shapiro (1972) and the 3-part (tripartite) subdivisions by Katsuta (1997) and Bernard (2018). CONCLUSIONS: The bipartite model has been criticized as being oversimplified and lacking surgical validity. However, support for this compartmentation has persisted despite the increasing popularity of the tripartite model. The 3-part subdivision of Bernard can be considered the most anatomically faithful model to date owing to the consideration of the dura and EDNAC. It is important that future studies consider the entire anatomy of the JF, which may generate an anatomically accurate and surgically applicable compartmental model.

The Jugular Process: A Key Anatomical Landmark for Approaches to the Jugular Foramen.

OBJECTIVE: To describe the morphology and anatomical relationship of the jugular process (JP) and to elucidate its utility as a surgical landmark in the lateraland posterior lateral approaches to the jugular foramen. MATERIALS AND METHODS: Eight dry adult skulls and 10 silicon-injected cadaver heads were used for this study. The distances to selected structures and the thickness of the JP at 3 selected sites were measured. We also included the data of 20 thin-sliced 3-dimensional computed tomography scans. The radiology data of these patients were transferred to a workstation for 3-dimensional reconstruction. RESULTS: The JP, an irregular trapezoid structure, is an important surgical landmark when approaching the jugular foramen. Laterally the JP is rough with 1 or 2 prominences to which the rectus capitis lateralis is attached. The JP is relatively flat medially. The condylar part of the occipital bone could be conceived as a "3-story building." The JP, hypoglossal canal, and lateral and posterior condylar emissary veins are located on the middle floor. The stylomastoid foramen is found constantly in the triangle formed by the styloid process, JP, and the base of the mastoid process. CONCLUSIONS: The JP is an important surgical landmark in the identification of jugular foramen, especially in the lateral and posterior approaches. A better understanding of its morphology and its relationship with the surrounding structures is a prerequisite for accurate surgical planning and intraoperative orientation.

Anatomical study of jugular foramen in the neck.

INTRODUCTION: The anatomical complexity of the jugular foramen makes surgical procedures in this region delicate and difficult. Due to the advances in surgical techniques, approaches to the jugular foramen became more frequent, requiring improvement of the knowledge of this region anatomy. OBJECTIVE: To study the anatomy of the jugular foramen, internal jugular vein and glossopharyngeal, vagus and accessory nerves, and to identify the anatomical relationships among these structures in the jugular foramen region and lateral-pharyngeal space. METHODS: A total of 60 sides of 30 non-embalmed cadavers were examined few hours after death. The diameters of the jugular foramen and its anatomical relationships were analyzed. RESULTS: The diameters of the jugular foramen and internal jugular vein were greater on the right side in most studied specimens. The inferior petrosal sinus ended in the internal jugular vein up to 40mm below the jugular foramen; in 5% of cases. The glossopharyngeal nerve exhibited an intimate anatomical relationship with the styloglossus muscle after exiting the skull, and the vagal nerve had a similar relationship with the hypoglossal nerve. The accessory nerve passed around the internal jugular vein via its anterior wall in 71.7% of cadavers. CONCLUSION: Anatomical variations were found in the dimensions of the jugular foramen and the internal jugular vein, which were larger in size on the right side of most studied bodies; variations also occurred in the trajectory and anatomical relationships of the nerves. The petrosal sinus can join the internal jugular vein below the foramen.

The Comparison of the Right and Left Sigmoid Sinus Cross-Sectional Areas in Fetal Period and the Factors Affecting the Venous Dominance.

OBJECTIVES: Skull base is an important and a challenging area for surgeons. Success in skull base surgery depends on various factors such as pre-operative evaluation, appropriate surgical technique, anesthesia duration, intraoperative neuromonitorization and wound care. MATERIALS AND METHODS: This study was performed in the Anatomy dissection laboratory of M.U. Medical Faculty (Ethical committee approval number 2010-103). Twelve fetuses between 17-33 gestational weeks fixed with formaldehyde were enrolled to the study. RESULTS: This study was planned to investigate the cross sectional areas of the sigmoid sinus in three levels to compare the right-left sides and the probable relationship among the levels in fetuses to further delineate the developmental factors on jugular foramen asymmetry. The cross-sectional measurements of sigmoid sinus lumen were done on 3 levels which are described as A1 level; sinodural angle, A2 level; the midpoint between the sinodural angle and endocranial orifice and A3 level as the entrance (endo-cranial orifice) of the jugular foramen. There is a strong positive correlation between left (L) A1 and L A2 and also the same for L A1 and right (R) A2. These strong and positive correlations are all valid between L A2-L A3, L A2-R A2, L A2-R A3, L A3-R A3, R A1-R A2. CONCLUSION: Multicenter studies would be beneficial to investigate the topic with greater number of fetuses also on the different regions for genetic differences.

Rectus Capitis Lateralis Muscle: A Cadaveric Study of a Key Surgical Landmark in the Posterior and Lateral Approaches to the Jugular Foramen.

OBJECTIVE: The rectus capitis lateralis (RCL) is a small cervical muscle that arises from the transverse process of C1 and is intimately related to the jugular process and jugular foramen. We describe its morphology, neurovascular relationships, and its utility as one of the key surgical landmarks in approaches to the jugular foramen. METHODS: Eight cadaveric heads were used to perform far-lateral and transmastoid approaches to the jugular foramen. The neurovascular relationships of the RCL were studied. RESULTS: The RCL originates from the transverse process of C1 and inserts onto the jugular process. It can be found in the muscular interval between the posterior belly of the digastric muscle and the superior oblique muscle with the occipital artery coursing between it and the posterior belly of the digastric muscle. It lies directly posterior to the internal jugular vein and cranial nerves (CNs) IX-XI as they exit the jugular foramen. The vertebral artery courses medially to the RCL as it exits foramen transversarium of C1. As the facial nerve exits the stylomastoid foramen, it is anterolateral to the RCL before turning to enter the parotid gland. The CN XII is seen between the RCL and the occipital condyle from a posterior view. CONCLUSIONS: The RCL usually is preserved unless jugular process needs to be removed to expose the jugular foramen. The RCL is an important surgical landmark for the early identification of the vertebral artery, internal jugular vein, facial nerve, and CNs IX-XII in approaches to the jugular foramen.

Microsurgical Anatomy of the Jugular Process as an Anatomical Landmark to Access the Jugular Foramen: A Cadaveric and Radiological Study.

BACKGROUND: The jugular process forms the posteroinferior surface of the jugular foramen and is an important structure for surgical approaches to the foramen. However, its morphological features have not been well described in modern texts. OBJECTIVE: To elucidate the microsurgical anatomy of the jugular process and examine its morphological features. METHODS: Five adult cadaveric specimens were dissected in a cadaveric study, and computed tomography data from 31 heads (62 sides) were examined using OsiriX (Pixmeo SARL, Bernex, Switzerland) to elucidate the morphological features of the jugular process. RESULTS: The cadaveric study showed that it has a close relationship with the sigmoid sinus, jugular bulb, rectus capitis lateralis, lateral atlanto-occipital ligament, and lateral and posterior condylar veins. The radiographic study showed that 9/62 sigmoid sinuses protruded inferiorly into the jugular process and that in 5/62 sides, this process was pneumatized. At the entry of the jugular foramen, if the temporal bone has a bulb-type jugular bulb, and if surgery concerns the right side of the head, the superior surface of the jugular process is more likely to be steep. CONCLUSION: The jugular process forms the posteroinferior border of the jugular foramen. Resection of the jugular process is a critical step for opening the jugular foramen from the posterior and lateral aspects. Understanding the morphological features of the jugular process, and preoperative and radiographical examination of this process thus help skull base surgeons to access the jugular foramen.