Introduction  The surgical management that achieves minimal morbidity and mortality for patients with glomus and non-glomus tumors involving the jugular foramen (JF) region requires a comprehensive understanding of the complex anatomy, anatomic variability, and pathological anatomy of this region. Objective  The aim of this study is to propose a rational guideline to expose and preserve the lower cranial nerves (CNs) in the lateral approach of the JF. Methods  The technique utilized is the gross and microdissection of 4 fixed cadaveric heads to revise the JF\'s surgical anatomy and high part of the carotid sheath compared with surgical cases to understand and preserve the integrity of lower CNs. The method involves radical mastoidectomy, microdissection of the JF, facial nerve, and high neck just below the carotid canal and the JF. The CNs IX, X, XI, and XII are microscopically dissected and kept in sight up to the JF. Results  This study realized well the surgical and applied anatomy of the lower CNs with relation to the facial nerve and JF. Conclusions  The JF anatomy is complicated, and the key to safely operate on it and preserving the lower CNs is to find the posterior belly of the digastric muscle, to skeletonize the facial nerve, to remove the mastoid tip preserving the stylomastoid foramen, to skeletonize the sigmoid sinus and posterior fossa dura not only anterior but also posteroinferior to reach and drill the jugular tubercle.

Objective  The jugular foramen is one of the most challenging surgical regions in skull base surgery. With the development of endoscopic techniques, the endoscopic endonasal approach (EEA) has been undertaken to treat some lesions in this area independently or combined with open approaches. The purpose of the current study is to describe the anatomical steps and landmarks for the EEA to the jugular foramen and to compare it with the degree of exposure obtained with the lateral infratemporal fossa approach. Materials and Methods  A total of 15 osseous structures related to the jugular foramen were measured in 33 adult dry skulls. Three silicone-injected adult cadaveric heads (six sides) were dissected for EEA and three heads (six sides) were used for a lateral infratemporal fossa approach (Fisch type A). The jugular foramen was exposed, relevant landmarks were demonstrated, and the distances between relevant landmarks and the jugular foramen were obtained. High-quality pictures were obtained. Results  The jugular foramen was accessed in all dissections by using either approach. Important anatomical landmarks for EEA include internal carotid artery (ICA), petroclival fissure, inferior petrosal sinus, jugular tubercle, and hypoglossal canal. The EEA exposed the anterior and medial parts of the jugular foramen, while the lateral infratemporal fossa approach (Fisch type A) exposed the lateral and posterior parts of the jugular foramen. With EEA, dissection and transposition of the facial nerve was avoided, but the upper parapharyngeal and paraclival ICA may need to be mobilized to adequately expose the jugular foramen. Conclusion  The EEA to the jugular foramen is anatomically feasible but requires mobilization of the ICA to provide access to the anterior and medial aspects of the jugular foramen. The lateral infratemporal approach requires facial nerve transposition to provide access to the lateral and posterior parts of the jugular foramen. A deep understanding of the complex anatomy of this region is paramount for safe and effective surgery of the jugular foramen. Both techniques may be complementary considering the different regions of the jugular foramen accessed with each approach.

OBJECTIVE: To investigate the feasibility of an endoscopic surgical approach through the neck to the jugular foramen, to determine the relevant techniques and extent of exposure, and to provide a new surgical approach with minimal trauma.
METHODS: Nine cadaveric head specimens with attached necks were fixed with 10% formalin solution. Two of the heads were fixed and injected with colored silicone rubber. Through the dissection of these cadaver head and neck specimens, we designed a surgical approach from the neck to the jugular foramen area with the use of a neuroendoscope and performed simulated surgery to determine which anatomical structures were encountered in the approach.
RESULTS: The posterior aspect of the internal jugular vein is adjacent to the rectus capitis lateralis. The internal carotid artery is anteromedial to the internal jugular vein, with the glossopharyngeal nerve, accessory nerve, vagus nerve and hypoglossal nerve in between. Removal of the rectus capitis lateralis can reveal the jugular process, and exposing the space between the superior oblique muscle and the jugular process can reveal the atlanto-occipital joint. Drilling through the occipital condyle can facilitate entrance into the skull, expose the flank of the medulla oblongata, and reveal the medullary olive and accessory nerve, vagus nerve, hypoglossal nerve, vertebral artery and posterior inferior cerebellar artery. Removing the jugular vein and completely opening the posterior wall of the jugular foramen can expose the inferior wall of the jugular bulb and the inferior wall of the sigmoid sinus. Drilling through the styloid process, which is lateral to the internal jugular vein, can expose the lateral area and upper wall of the jugular bulb and cranial nerves (CN) IX-XII; and near the top of the jugular bulb, the tympanic cavity and the external auditory canal can be easily opened.
CONCLUSIONS: Endoscopic surgical access from the neck to the jugular foramen is feasible. This surgical approach can simultaneously remove intracranial and extracranial tumors and can also be used to remove tumors in the ventral region of the occipital foramen and the hypoglossal canal. Furthermore, this approach is advantageous in that minimal trauma is inflicted. With judicious patient selection, this approach may have significant advantages and may be used as a primary or secondary surgical approach in the future. Nonetheless, this approach is still in development in a laboratory setting, and further research and improvements are needed before facing more complicated situations in clinical practice.

UNASSIGNED: Neurological presentation with isolated multiple cranial nerve palsies is common and its diverse causes include infectious, neoplastic, and inflammatory pathologies. The aetiological spectrum may depend upon geographical regions. We undertook this study to explore clinical spectrum and aetiological profile of multiple cranial nerve palsies.
UNASSIGNED: This hospital-based prospective observational study was conducted from August 2015 to August 2017. All the consecutive patients of multiple cranial palsies presenting to the neurology department were included in the studies. Primary objectives were to define anatomical syndromes/cranial nerve combinations and to establish aetiology. Secondary objectives were to study associated factors. The multiple cranial nerve palsy was defined as involvement of two or more non-homologous nerves. Patients of neuromuscular junction disorders, anterior horn cell disorders, myopathies, brain stem syndromes were excluded. All patients underwent structured protocol of clinical evaluation, investigations and few specialized investigations in accordance with clinical suspicion to establish the diagnosis.
UNASSIGNED: Fifty-four patients with a mean age of 39.9 ± 14.2 years were included. Commonest cranial nerve involved was the abducens (75.9%) among all nerve combinations. The cavernous sinus syndrome (37%), orbital apex syndrome (22.2%) and jugular foramen syndrome (11.1%) were the most frequent anatomical patterns. Infections (40.7%) were the commonest aetiology followed by neoplastic and idiopathic in four patients.
UNASSIGNED: Cavernous sinus syndrome was the commonest anatomical syndrome of multiple cranial nerve palsies and infections were the commonest cause in this study.

The extradural neural axis compartment (EDNAC) is an adipovenous zone that is located between the meningeal (ML) and endosteal (EL) layers of the dura mater and has been minimally investigated in the jugular foramen (JF) region. In this study, the authors aimed to explore the fine architecture of the EDNAC within the JF and evaluate whether the EDNAC can be used as a component for JF compartmentalization.
A total of 46 cadaveric heads (31 male, 15 female; age range 54-96 years) and 30 dry skulls were examined in this study. Twelve of 46 cadaveric heads were plastinated as a series of transverse (7 sets), coronal (3 sets), and sagittal (2 sets) slices and examined using stereomicroscopy and confocal microscopy. The dural entry points of the JF cranial nerves were recorded in 34 cadaveric skulls. The volumes of the JF, intraforaminal EDNAC, and internal jugular vein (IJV) were quantified.
Based on constant osseous landmarks, the JF was subdivided into preforaminal, intraforaminal, and subforaminal segments. The ML-derived fascial sheath along the anteromedial wall of the IJV demarcated the \"venous portion\" and the \"EDNAC portion\" of the bipartite JF. The EDNAC did not surround the intraforaminal IJV and comprised an ML-derived dural fibrous network and an adipose matrix. A fibrovenous curtain subdivided the intraforaminal EDNAC into a small anterior column containing cranial nerve (CN) IX and the anterior condylar venous plexus and a large posterior adipose column containing CNs X and XI. In the intraforaminal segment, the IJV occupied a slightly larger space in the foramen (57%; p < 0.01), whereas in the subforaminal segment it occupied a space of similar size to that of the EDNAC.
Excluding the IJV, the neurovascular structures in the JF traverse the dural fibrous network that is dominant in the foraminal EDNAC. The results of this study will contribute to anatomical knowledge of the obscure yet crucially important JF region, increase understanding of foraminal tumor growth and spread patterns, and facilitate the planning and execution of surgical interventions.

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.
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.
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).
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.

Access to the jugular foramen (JF) requires extensive approaches. An endoscopic endonasal far medial (EEFM) approach combined with a postauricular transtemporal (PTT) approach may provide adequate exposure with limited morbidities.
To provide a quantitative anatomic comparison of the EEFM, the PTT, and the combined EEFM/PTT approaches. A clinical case of the combined approach is presented.
Five cadaveric heads were dissected. Each specimen received PTT and EEFM approaches on opposite sides followed by an EEFM approach on the side of the PTT approach. Morphometric and quadrant analyses were conducted. Three groups were obtained and compared: PTT (group A), EEFM (group B), and combined (group C).
Group B had a significantly higher area of exposure of the JF as compared to group A (112.3 and 225 mm2, respectively, P = .004). The average degree of freedom (DOF) in the cranio-caudal plane for groups A and B was 63.6 and 12.6 degrees, respectively (P < .00001). Group A had a higher DOF in the medial-lateral plane than group B (49 vs 13.4 degrees, respectively, P < .00001. The average volume of exposure in groups A and B was 1469.2 and 1897.4 mm3, respectively (P = .02). By adding an EEFM approach to the PTT approach, an additional 56.1% of the anterior quadrant was exposed, representing a 584.4% increase in the anterior exposure.
The PTT and EEFM approaches provide optimal exposures to different aspects of the JF and in combination may constitute a less invasive alternative to the more extensive approaches.

Introduction  The jugular foramen occupies a complex and deep location between the skull base and the distal-lateral-cervical region. We propose a morphometric anatomical model to deconstruct its surgical anatomy and offer various quantifiable target-guided exposures and angles-of-attack. Methods  Six cadaveric heads (12 sides) were dissected using a combined postauricular infralabyrinthine and distal transcervical approach with additional anterior transstyloid and posterior far lateral exposures. We identified anatomical landmarks and combined new and previously described contiguous triangles to expose the region; we defined the jugular and deep condylar triangles. Angles-of-attack to the jugular foramen were measured after removing the digastric muscle, styloid process, rectus capitis lateralis, and occipital condyle. Results  Removing the digastric muscle and styloid process allowed 86.4° laterally and 85.5° anteriorly, respectively. Resecting the rectus capitis lateralis and jugular process provided the largest angle-of-attack (108.4° posteriorly). The occipital condyle can be drilled in the deep condylar triangle only adding 30.4° medially. A purely lateral approach provided a total of 280.3°. Cutting the jugular ring and mobilizing the vein can further expand the medial exposure. Conclusion  The microsurgical anatomy of the jugular foramen can be deconstructed using a morphometric model, permitting a surgical approach customized to the pathology of interest.

BACKGROUND: The lower clivus (LC) is one of the most difficult areas to access in neurosurgery. Several microsurgical approaches to the LC have been reported, including the subtonsillar, far-lateral (FL), extreme-lateral (EL), and endoscopic far-medial (Endo-FM). However, no consensus has been reached regarding the optimal approach. We aimed to quantify and compare the surgical exposure and freedom (angle of attack) for various targets at the LC using these 4 surgical approaches.
METHODS: The subtonsillar, FL, EL, and Endo-FM approaches were performed on 5 cadaveric specimens (total 10 sides). Surgical exposure and freedom were measured using the neuronavigation system.
RESULTS: At the LC, the Endo-FM approach provided the greatest area of exposure (459.3 ± 82.2 mm2). For surgical freedom, the EL approach provided the greatest angle of attack at the jugular foramen (98.1° ± 9.2°) and hypoglossal canal (128.8° ± 26.1°). The Endo-FM was the only approach that provided access to the midline of the LC in all specimens. However, the surgical freedom at the midline (20.9° ± 2.4° at the level of the jugular foramen; 24.2° ± 2.9° at the level of hypoglossal canal) was limited by its deep surgical corridor (104.3 ± 11.2 mm) compared with the EL and FL approaches.
CONCLUSIONS: The Endo-FM approach provided the greatest surgical freedom at the ventral aspect but the least freedom at the lateral aspect. The EL approach provided maximal values for most parameters among the open approaches; however, the craniotomy with the EL approach was the most complicated. Our quantitative results could guide neurosurgeons in preoperative planning for LC lesions, including awareness of the maximum exposure limits and the advantages and disadvantages of each surgical approach.

OBJECTIVE: This 3-dimensional histologic study aimed to provide a precise description of the meningeal structures in the jugular foramen.
METHODS: 22 posterior skull base tissue blocks containing the jugular foramen region were obtained from 11 human cadaveric heads. These blocks were plastinated and cut into serial sections. After staining, these sections were examined under an optical microscope and used to reconstruct a 3-dimensional visualization model.
RESULTS: At the intracranial orifice of the jugular foramen, the meningeal dura formed 2 separate dural perforations: the glossopharyngeal meatus and the vagal meatus. The arachnoid extended into 2 dural meatuses and terminated at the inferior ganglion of the glossopharyngeal nerve in the glossopharyngeal meatus and the superior ganglion of the vagus nerve in the vagal meatus. At the intraforaminal part of the jugular foramen, the meningeal dura encased the glossopharyngeal nerve to form a dural sheath while encasing the vagus and accessory nerves to form a dural network. At the extracranial orifice of the jugular foramen, the dural wall of the jugular bulb extended downward to form a dense connective tissue sheath. The initial end of the internal jugular vein invaginated into this sheath and fused with the jugular bulb.
CONCLUSIONS: Knowledge of the anatomy of the meningeal architecture of the jugular foramen can be helpful in avoiding surgical complications of the lower cranial nerves when this complex area is approached.