Approaches to the jugular foramen can be challenging. Adding to this difficulty is the potential for a bony septation to occur in the foramen thus subdividing its contents. Although such bony septations in the jugular foramen are known, the anatomic details of these structures have not been studied well. Therefore, the present anatomic study was performed.
One hundred adult human skulls (200 sides) underwent evaluation for the presence or absence of a bony septation within the jugular foramen. The source, morphology, and size were all documented. A classification scheme was developed to better describe the varied types of morphology of the jugular foramen bony septa. Select bony septations were submitted to histologic analysis using hematoxylin and eosin and Masson\'s trichrome.
Bony bridges were found on 8.5% of sides. These were bilateral in 3% of skulls. Eight (47%) were incomplete (type I). Nine sides (53%) were found to have completely articulated bony bridges (type II) and these had articulation between the bony processes as either touching (type IIa), joint-like (type IIb), or completely fused (type IIc) morphologies. Multiple septa were observed on 2.5% of sides and these were classified as type III septa. Histologically, both incomplete and complete septa were found to be composed of normal bone tissue.
Our study found significant variations regarding the bony septa of the jugular foramen. Knowledge of this anatomy can be useful for preoperative planning and intraoperative navigation with approaches to the skull base that target pathology of the jugular foramen.

To identify MRI-based quantitative craniofacial variables linked to airways narrowing and obstructive sleep apnea (OSA) development in children with achondroplasia.
We evaluated skull base and midface MRI in two cohorts of children affected by achondroplasia, with (group 1) or without OSA (group 2). 3DFSPGR-T1weighted images were used to assess airways volume (nasopharynx, oropharynx, and laryngopharynx), jugular foramina (JF) and hypoglossal foramina (HF) areas, foramen magnum area, cervical cord area, and maxillary retrusion (SNA angle).
Nineteen out of 27 children with achondroplasia exhibited different degrees of obstructive respiratory impairment (n.4 mild, n.8 moderate, n.7 severe), while 8 children did not show OSA. Each group was compared with age-matched controls without neuroimaging abnormalities. Both groups showed reduced nasopharynx volume, JF areas, and SNA angle, while group 1 showed also reduced oropharynx volume, ratio of FM/cervical cord areas, and HF areas (p < 0.05). A positive correlation between nasopharynx volume and SNA angle was found in both groups, while a positive correlation among upper airways volume, JF and HF areas was found only in group 1. No correlation between upper airways volume and OSA severity was found.
In children with achondroplasia, multifaced craniofacial abnormalities contribute to airways volume reduction predisposing to sleep disordered breathing. MRI-based quantitative assessment allows the appraisal of craniofacial variables linked to the development of sleep-disordered breathing such as FM stenosis, jugular and hypoglossal foramina stenosis, and retruded maxillary position and may be a valuable tool for clinical surveillance.

BACKGROUND: Most infants and children with achondroplasia show delayed motor skill development; however, some patients may have clinical consequences related to cranio-cervical junction stenosis and compression.
OBJECTIVE: To assess, using brain magnetic resonance imaging (MRI), quantitative variables linked to neuromotor impairment in achondroplasic children.
METHODS: In total, 24 achondroplasic children underwent pediatric neurological assessment and were grouped in two cohorts according to relevant motor skill impairment. Achondroplasic children with (n=12) and without (n=12) motor symptoms were identified, and brain MRI scans were quantitatively evaluated. 3D fast spoiled gradient echo T1-weighted images were used to assess: supratentorial intracranial volumes (SICV); supratentorial intracranial brain volume (SICBV); SICV/SICBV ratio; posterior cranial fossa volume (PCFV); posterior cranial fossa brain volume (PCBFV); PCFV/PCFBV ratio; ventricular and extra-ventricular cerebrospinal fluid (CSF) volumes; foramen magnum (FM) area; and jugular foramina (JF) areas.
RESULTS: In both groups, SICV/SICBV ratio, supratentorial ventricular and extra-ventricular space volumes were increased while SICBV was increased only in the asymptomatic group (P < 0.05). PCFV/PCFBV ratio, IV ventricle, infratentorial extra-ventricular spaces volumes were reduced (P < 0.05) in the symptomatic group while PCFBV was increased only in the asymptomatic group (P < 0.05). Foramen magnum (FM) area was more reduced in the symptomatic group than the asymptomatic group (P < 0.05) but no correlation between FM area and ventriculomegaly was found (P > 0.05).
CONCLUSIONS: Evaluation of the FM area together with infratentorial ventricular and extra-ventricular space volume reduction may be helpful in differentiating patients at risk of developing motor skill impairment. Further investigation is needed to better understand the temporal profile between imaging and motor function in order to propose possible personalized surgical treatment.

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.

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.

Extracranial venous anomalies, especially internal jugular vein stenosis (IJVS), have recently received increasing attention, however, its etiologies are uncertain. This study aimed to explore the probable risk factors of IJVS in Chinese PATIENTS AND METHODS: Eligible patients with IJVS confirmed by contrast-enhanced magnetic resonance venography (CE-MRV) were enrolled from October 2017 through October 2018. Probable risk factors were analyzed, including the conditions that may result in IJV wall damage, extraluminal compression, gender and age.
A total of 133 patients enrolled in the final analysis, including 73 females and 60 males, the mean age were 54.83 ± 15.25 years. In this IJVS cohort, the top two risks were previous hepatitis B virus (HBV) infection (48.9 %) and osseous compression (41.4 %). The IJVS cohort was divided into two subsets: extraluminal compression and non-compression. In the former, osseous compression (80.9 %) was the top risk factor, other risks including arterial (22.1 %) and lymph node compression (2.9 %). While, in the latter subset, the most common risk factor was previous HBV infection (46.2 %). In addition, cerebral venous sinus thrombosis (CVST) in non-compression subset was more common than that in extraluminal compression subset (21.5 % VS. 2.9 %, p = 0.001). When considered the gender (Male vs. Female), the ratios were 28.3 % vs. 0 % of smoking, p < 0.001, 16.67 % vs. 1.37 % of hyperhomocysteinemia, p = 0.002, and 11.67 % vs. 1.37 % of hyperuricemia, p = 0.023. In the subset with age less than 45 years, the top three risks included CVST (56.25 %), immunological diseases (55.56 %), and hyperhomocysteinemia (50.00 %), while, in the subset with the ages over 60 years, type-2 diabetes (66.66 %), carotid artery compression (53.33 %), previous HBV infection (52.31 %), and osseous compression (49.09 %) were more common than others.
This study illustrates the probable risks of IJVS may be diverse, in which osseous compression and previous HBV infection may be the top two probable risks of IJVS in Chinese. This is the biggest difference from previous reports based on Caucasian.

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.

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.

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.
To elucidate the microsurgical anatomy of the jugular process and examine its morphological features.
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.
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.
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.