Microsurgical Anatomy of the Jugular Foramen Applied to Surgery of Glomus Jugulare via Craniocervical Approach

Impact of Sigmoid Sinus Anatomy on Assessing the Feasibility of the Retrofacial Access to the Entire Jugular Fossa Before Surgery

BACKGROUND AND OBJECTIVES

The jugular fossa (JF) is a challenging area for surgical approaches because of its complex anatomy and proximity to neurovascular structures. The study evaluates the feasibility of the neuronavigated microsurgical transmastoid extended infralabyrinthine extradural retrofacial approach (mTEIER-A) in human head specimens for accessing the entire intraosseous JF in relation to the position of the sigmoid sinus (SS), horizontal angle of attack, and size of the SS.

METHODS

The mTEIER-A was performed on human head specimens. Before dissection, the position of the SS, horizontal angle of attack, and size of the SS were measured on tilted axial high resolution computed tomography scans; after dissection, access to the lateral aspect of the JF on dissected human head specimens and on postoperative high-resolution computed tomography scans was examined. The position of the SS was classified relative to a predefined reference line, and the feasibility of retrofacial access was documented.

RESULTS

SS positions located medial to the reference line (P1) and horizontal angles >12.5° significantly enhance retrofacial access to the lateral aspect of the JF, whereas the size of the SS has a limited impact.

CONCLUSION

Depending on the position of the SS and the horizontal angle of access, mTEIER-A provides sufficient retrofacial access to the lateral aspect of the JF. These findings emphasize the need for precise preoperative planning and suggest that mTEIER-A could minimize the need for more invasive approaches, potentially reducing related morbidity. Further clinical studies are recommended to validate these findings.

Sheep Head Cadaveric Model for the Transmeatal Extensions of the Retrosigmoid Approach

The transmeatal extension of the retrosigmoid approach is an important procedure used in the treatment of various pathologies affecting the posterior fossa, petroclival region, and jugular foramen. Mastering this technique requires a high level of manual skill, particularly in temporal bone drilling. The objective of this study was to describe an easily accessible and cost-effective model of the transmeatal extension of the retrosigmoid approach using cadaveric sheep heads. Five cadaveric sheep heads, fixed in alcohol and formalin with intravascular-colored silicone injection, were prepared for this study. Two heads (four sides) were designated for illustrative anatomical specimens, while three heads (six sides) were used for surgical simulation. Additionally, one head was used to prepare and dissect a dry skull. All critical steps of the transmeatal approach, including both supra- and inframeatal extensions, were successfully replicated on the model. A comparative anatomical analysis was conducted, focusing on the technical nuances of the model. The cadaveric sheep head serves as an effective model for the retrosigmoid approach with transmeatal extensions, primarily for training manual haptic skills. While the sheep model cannot precisely replicate human anatomy, it still offers valuable training opportunities for neurosurgeons, particularly when human cadaveric specimens are unavailable.

Review of the caroticotympanic nerves: Anatomy, function and pathology

The caroticotympanic nerves provide postganglionic sympathetic fibres to the tympanic plexus. However, there are scant reports in the literature detailing with these nerves in great depth. As the caroticotympanic plexus lies near the often-operated tympanic nerve, it is important for the surgeon to understand the anatomy, pathology and surgical implications of it. Here, we present a review of the available literature regarding the caroticotympanic nerves.

Modern Management of Complex Tympanojugular Paragangliomas: Systematic Review and Meta-Analysis

OBJECTIVE

Tympanojugular paragangliomas (TJPs) are slow-growing tumors arising within the middle ear or jugular foramen. The development of modified skull base approaches and the increasing use of stereotactic radiosurgery have provided more modern techniques in the management of TJPs. Several factors dictating approach selection, and resulting clinical outcomes have been inconsistently described.

METHODS

A systematic review of the literature describing modern management of complex TJPs was performed and summarized. A random-effects meta-analysis was performed to describe the rate of tumor control, complications, and symptom improvement in patients undergoing radiosurgery or surgical resection.

RESULTS

Nineteen studies were identified with a total of 852 TJP patients. A minority (153 patients) underwent radiosurgery while 699 underwent surgery. On meta-analysis, there was a 3.5% (95% confidence interval [CI]: 0.5%-6.4%) tumor growth rate following radiosurgery and 3.9% (95% confidence interval [CI]: 1.8%-6.0%) recurrence rate in surgical resection, with no significant moderator effect between the 2 groups (P = 0.9046). Complication rate for radiosurgery was 7.6% (95% CI: 2.8%-12.4%), differing significantly from surgical complication rates of 29.6% (95% CI: 17.1-42.0%, P = 0.0418).

CONCLUSIONS

Stereotactic radiosurgery and surgical resection for TJPs have similar rates of tumor recurrence. Radiation is associated with less risk and lower morbidity, yet there is comparably modest reduction of the tumor size. In sum, the data suggest that radiosurgery is a reasonable management option for patients with minimal symptoms who are high risk for surgery. Microsurgical resection should be reserved for patients with lower cranial neuropathies or those who have failed radiation treatment.

Variations and Classification of Bony Septations of the Jugular Foramen: An Anatomic and Histologic Study With Application to Imaging and Surgery of the Skull Base

INTRODUCTION

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Surgical treatment of selected tumors via the navigated minimally invasive presigmoidal suprabulbar infralabyrinthine approach without rerouting of the facial nerve

The feasibility of a novel skull base approach - the navigated minimally invasive presigmoidal suprabulbar infralabyrinthine approach (NaMIPSI-A) without rerouting of the fallopian canal for selected jugular foramen tumors (JFTs) - has been demonstrated in a neuroanatomical laboratory study. Here, we present our clinical experience with the NaMIPSI-A for selected JFTs, with a particular focus on its efficacy and safety. All patients with JFTs who were treated via the NaMIPSI-A were included in this study. The JFTs were classified according to a modified Fisch classification. The neurological and neuroradiological outcome, the extent of tumor resection, and the approach-related morbidity were examined. Five patients (two women, three men; mean age 57 years, range 48-65) were available. According to the modified Fisch classification, two JFTs were graded as C1, one as De1, and two as De2. Gross total resection (GTR) was achieved in three patients and near-total resection (NTR) in two. Postsurgically, no new neurological deficits and no approach-related morbidity and mortality occurred. One case with a postoperative cerebrospinal fluid leak was managed successfully with lumbar drainage. During the follow-up period (mean 67.6 months, range 12-119 months), tumor recurrence was noted in the NTR group but not in the GTR group. The NaMIPSI-A to the jugular foramen without rerouting of the fallopian canal is highly valuable for selected tumors of the jugular foramen. It is less invasive than other skull base approaches, and it allows safe and complete tumor removal in appropriate patients.

The posterior ligament of the incus ("white dot"): A reliable surgical landmark for the facial recess

OBJECTIVE

There is a void in the literature describing reliable surgical landmarks that aid in the dissection of the facial recess in the absence of skeletonizing the mastoid segment of the facial nerve. The posterior ligament of the incus is a readily distinguishable "white dot" along the incus buttress that has been used to guide dissection in a safe and efficient manner. The goal of our study is to describe a surgical approach that utilizes this surgical landmark to drill the facial recess and to take anatomical measurements demonstrating the safety and reliability of this approach.

MATERIALS AND METHODS

After cortical mastoidectomies were performed in 10 cadaveric temporal bones, the white dot was identified at the junction of short process of the incus and the incus buttress. Using the white dot for anatomical reference, a 2 mm diamond drill bit was used to open the facial recess without first identifying the facial nerve or chorda tympani nerve. After photographs were taken, the facial and chorda tympani nerves were definitively identified and skeletonized to delineate the confines of the facial recess. Photographs were once again acquired in a consistent manner for comparison. Finally, calibrated anatomic measurements were acquired from the 10 distinct image sets.

RESULTS

The facial recess was successfully drilled in 10 temporal bones using the posterior ligament as a surgical landmark without injury to the chorda tympani or facial nerve. The median angle taken from the axis of the short process of the incus to the facial nerve - chorda tympani junction was 139.2° (IQR 136.8-141). At the widest point in the facial recess, median distances anterior and posterior to an imaginary line connecting the white dot to the facial nerve - chorda tympani junction were 1.6 mm (IQR 1.5-1.7) and 1.6 mm (IQR 1.6-1.7; p = 0.57), indicating at this point, the white dot reference reliably bisects the facial recess width. Similarly, at the level of the round window niche, median anterior and posterior distances from an imaginary line connecting the white dot to the facial nerve - chorda tympani junction were 1.1 mm (IQR 1.1-1.3) and 1.3 mm (IQR 1.1-1.7; p = 0.07), respectively, once again demonstrating the white dot reliably bisecting the facial recess.

CONCLUSIONS

The white dot, representing the posterior ligament of the incus, is a reliable surgical landmark that aids in safe and efficient drilling of the facial recess without first skeletonizing the facial nerve.

Comparison of Endoscopic Endonasal Approach and Lateral Microsurgical Infratemporal Fossa Approach to the Jugular Foramen: An Anatomical Study

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.

A CHALLENGING CASE OF SPORADIC MELANOCYTOMA OF THE JUGULAR FORAMEN

BACKGROUND

The jugular foramen (JF) can be the site of several tumours. Paragangliomas, schwannomas and meningiomas are the most commonly reported. We describe a case of melanocytoma originating from the JF and presenting with an accessory nerve palsy. Illustrative case: A 48-year-old woman presented with a 6-month history of cervical and left shoulder pain with wasting and weakness of the left trapezius. A Magnetic Resonance Imaging (MRI) showed a T1-hyperintense, T2-isointense, heterogeneously enhancing lesion involving the left JF and extending into the cerebello-medullary and cerebello-pontine cisterns. A retrosigmoid craniotomy was performed and a near total removal achieved. The accessory nerve was involved by tumour and could not be preserved. Given the diagnostic uncertainty between melanotic schwannoma, metastatic melanoma and meningeal melanocytoma, next generation sequencing and genome-wide DNA methylation arrays were performed, documenting a mutation in GNA11 (c.6226A>T, p. Gln209Leu) and a methylation profile consistent with melanocytoma. The patient underwent adjuvant fractionated radiotherapy of the tumour remnant. A follow-up MRI 4 years after surgery did not show any tumour recurrence.

CONCLUSIONS

The differential diagnosis of skull base pigmented tumours can be challenging, particularly when they occur in unusual locations such as the JF. They can be misdiagnosed given their similar clinical, neuroradiological and pathological features if anatomy of the site of origin is not carefully considered and molecular tests are not performed, leading to erroneous treatment and follow up planning.