Predicting the presigmoid retrolabyrinthine space using a sigmoid sinus tomography classification: A cadaveric study

Evaluation of the Sigmoid Sinus Morphology by Cone Beam Computed Tomography; Touchstone of the Posterior Cranial Fossa

OBJECTIVE

In this study, we aimed to analyze the relationship of the sigmoid sinus (SS) with the external auditory canal, facial nerve, and mastoid cells from an anatomic point of view, to define the position of the SS during transmastoid, translabyrinthine, retrosigmoid (lateral suboccipital) approaches, in tympanomastoidectomy and posterior cranial fossa surgery.

METHODS

In this study, the morphologic structures associated with the sigmoid sinus were evaluated in cone beam computed tomography images taken between 2015 and 2022. The images of 68 men and 106 women, aged 18-65 years, obtained from the archive of Ankara University Faculty of Dentistry, Department of Oral and Maxillofacial Radiology were analyzed.

RESULTS

The most common SS pattern was type II, with a rate of 60.8% (n = 209); the second was type III, with 20.6% (n = 71); and the least common was type I, with 18.6% (n = 64). Although the distance between the horizontal line passing through the external auditory canal and facial nerve and the anterior contour of the SS was highest in type I (right, 7.26 ± 1.62; left, 7.44 ± 0.97), it was lowest in type III (right, 4.40 ± 1.50; left, 4.84 ± 1.16) (P < 0.05).

CONCLUSIONS

This study highlights the importance of the SS position in surgery, with special reference to otologic, neurotologic, and posterior cranial fossa surgery. To avoid intraoperative complications, each patient should be evaluated preoperatively by appropriate radiologic methods.

Operational Analysis of Trautman's Triangle in Petroclival Region Approaches: Cone-Beam Computed Tomography Study

OBJECTIVE

This study was conducted to evaluate the anatomical and clinical features of Trautman's triangle (TT) and to better understand the possible surgical corridor for other surgical approaches involving the petroclival region, especially the presigmoid retrolabyrinthine approach.

METHODS

In this study, morphological analysis of structures related to TT was performed from cone beam computed tomography images of 134 female and 206 male individuals aged 18-65 years.

RESULTS

The TT area was observed as 5.6% (n = 19) type I, 63.2% (n = 215) type II, and 31.2% (n = 106) type III. It was determined that 87.6% of the sigmoid sinus (SS) was lateral to the posterior semicircular canal and 12.4% was medial. It was determined that the TT area showed a positive correlation with petrous slope and a negative correlation with mastoid aeration. In other words, as the TT area increased, the petrous inclination angle also increased, but the mastoid aeration decreased. It was also found that the TT area was associated with the location of the SS and the largest TT area (164.84 ± 42.29 mm2) was observed in the posteriorly located SS.

CONCLUSIONS

The relationship between TT and SS, petroclival angle, mastoid aeration, and subarcuate fossa has a very dynamic structure. Understanding the variations and clinical significance of these structures in the petroclival region is critical in determining the surgical approaches to be applied and understanding the etiology of vestibular system diseases.

Clinical correlation research of 3D reconstruction of retrolabyrinthine space based on HRCT of temporal bone

Background: The retrolabyrinthine approach helps clinicians perform complex surgeries such as vestibular neurectomy, resection of petrous apex cholesteatoma, or use this space to complete endoscopic combined with microscope surgical operations in a relatively safe buffer space. Some of our current studies using 3D reconstruction in the clinic have also helped us perform some complex surgical procedures.Objective: This study aims to reveal the relationship between important structures in retrolabyrinthine space through objective parameters. These measurement data help clinicians locate intraoperatively and provide a reference for clinical surgery. Also, we are intended to help improve surgical techniques and expand the operating space to increase reachable anatomic structure.Material and Methods: The inner structures of the temporal bone from HRCT (High-resolution computed tomography) images which were taken at the Eye & ENT Hospital of Fudan University were reconstructed. Precise measurement of the structures was accomplished by using the software 3D-Slicer (3D Slicer, https://www.slicer.org/; version 4.8.0, Massachusetts, USA).Results: 3D model of temporal bone structures, including the cochlea, semicircular canals (SCCs), the internal auditory canal (IAC), facial nerve (FN), jugular bulb(JB), and carotid artery was reconstructed. The combination of HRCT and 3D models is utilized to analyze the Quantitative data of the retrolabyrinthine space and its adjacent structures.Conclusions and Significance: 3D reconstruction of CT images clearly displayed the detailed structures of the temporal bone. Surgical adaptability of the retrolabyrinthine approach can be assessed preoperatively by image and other methods, and anatomical parameters play an important role in the retrolabyrinthine space. Therefore, this study helps to skeleton the bone as much as possible to expand the surgical space, so that the surgeon can contact the anatomical structure more diversified to expand the surgical indications.

Long-Term Hearing Stability at Different Frequencies after Lower Intact Bridge Tympanomastoidectomy and Possible Theoretical Basis

Objective: We aimed to review the long-term hearing outcomes of intact bridge tympanomastoidectomy (IBM) to discuss hearing preservation and combine the theory of "modified miniature lung," middle ear ventilation, and gas pressure balance theory to explore the possible reasons for long-term stable hearing. Study Design: We designed a collection of patients with chronic suppurative otitis media (CSOM) who underwent IBM and divided them into 2 groups to compare long-term and short-term hearing level. Setting: From April 2007 to July 2017, 102 patients received IBM for CSOM treatment in Eye & ENT Hospital of Fudan University. Methods: We divided the patients into 2 groups according to whether the follow-up period was longer than 6 months. We used the numerical value of the air-bone gap difference as an index to evaluate the degree of hearing recovery. Results: We found that 99/102 (97.1%) of the hearings were improved to more than 3 frequencies. There was no significant difference between long-term hearing level and short-term hearing level, which means IBM could get long-term hearing stability. Conclusion: Intact bridge tympanomastoidectomy could provide significant hearing recovery and long-term hearing stability.

Midline Skull Base Meningiomas: Transcranial and Endonasal Perspectives

Simple Summary

Skull base meningiomas have always represented a challenge for neurosurgeons. Despite their histological nature, they may be associated with unfavorable outcomes due to their deep-seated location and the surrounding neurovascular structures. Over time, several corridors have been proposed, each one carrying its own pros and cons. During the last decades, the endoscopic endonasal route has been asserted among the classic routes for a growing number of midline and paramedian lesions. Therefore, the aim of our paper is to present a comprehensive review of the indications and techniques for the management of skull base meningiomas, emphasizing the ambivalent and complementary role of the low and high routes.

Abstract

Skull base meningiomas have always represented a challenge for neurosurgeons. Despite their histological nature, they may be associated with unfavorable outcomes due to their deep-seated location and the surrounding neurovascular structures. The state of the art of skull base meningiomas accounts for both transcranial, or high, and endonasal, or low, routes. A comprehensive review of the pertinent literature was performed to address the surgical strategies and outcomes of skull base meningioma patients treated through a transcranial approach, an endoscopic endonasal approach (EEA), or both. Three databases (PubMed, Ovid Medline, and Ovid Embase) have been searched. The review of the literature provided 328 papers reporting the surgical, oncological, and clinical results of different approaches for the treatment of skull base meningiomas. The most suitable surgical corridors for olfactory groove, tuberculum sellae, clival and petroclival and cavernous sinus meningiomas have been analyzed. The EEA was proven to be associated with a lower extent of resection rates and better clinical outcomes compared with transcranial corridors, offering the possibility of achieving the so-called maximal safe resection.

The presigmoid retrolabyrinthine approach: Technical note

BACKGROUND

The retrolabyrinthine approach is classified among the posterior petrosectomies. Its goal is to achieve an enlarged mastoidectomy while sparing the intrapetrous neurotologic structures in order to offer maximal exposure of the posterior cerebellopontine angle compound.

METHODS

The stages of the procedure are subsequently the skeletonization of the sigmoid sinus, wide opening of the mastoid antrum and exposure of the semicircular canals. We present herein the technique, indications and limitations of the retrolabyrinthine approach.

CONCLUSION

The retrolabyrinthine approach is a demanding technique. Nowadays the retrolabyrinthine approach is routinely combined to additional resections of the petrous bone, so-called "combined petrosectomies", to target the jugular foramen or the petroclival area.

The historical perspective in approaches to the spheno-petro-clival meningiomas

The current literature regarding surgical treatment for tumors in the sphenopetroclival (SPC) region is merely scarce. Through a comprehensive literature review, we investigated the indications, outcomes, and complications of different surgical approaches to the SPC meningiomas. Given its complicated relationship between these slow-progression tumors and some critical neurovascular structures in the SPC region, surgical treatment of these tumors faces the challenge of achieving a maximal grade of resection, while preserving patient functionality. The development of new surgical techniques and approaches in recent years have permitted the advancement in the treatment of these tumors, with acceptable rates of morbidity and mortality. The choice of a surgical approach as a treatment for the lesion depends mainly on the type of tumor extension, surgeon's preferences, and the displacement of neurovascular structures. Rather than focusing on one single strategy of treatment, the skull-base surgeon should tailor the approach based on the origin and features of the lesion; as well as the peculiarities of the surgical anatomy. This strategy aims to decrease morbidity and to optimize tumor resection and patient quality of life.

Study of Sigmoid Sinus Variations in the Temporal Bone by Micro Dissection and its Classification - A Cadaveric Study

Introduction  Sigmoid sinus (SS) variations have been classified variously in the literature. These classifications suffer from some form of shortcoming from a clinical point of view for their application.

Objective  We propose a clinically relevant classification of the SS in relation to the posterior semicircular canal (PSCC) and to the exposure of the presigmoid dural plate. The positioning of the SS was analyzed with reference to the volume of the mastoid and to the level of mastoid pneumatization.

Methods  A total of 94 formalin-preserved human cadaveric temporal bones were microdissected to carry out a complete mastoidectomy. The SS, the presigmoid dural plate, and the PSCC were exposed, and the position of the former was analyzed in relation to the latter two in order to classify the position of the SS into three grades.

Results  Grade I had the best exposure of the presigmoid dura and of the PSCC, while grade III had the poorest exposure of the presigmoid dura and of the PSCC. Grade I SS was associated with good pneumatization and higher mastoid volumes compared with grades II and III.

Conclusions  The SS exhibits considerable anatomic variability. A favorable positioning of the SS is associated with a large mastoid volume and pneumatization. A careful preoperative study of the imaging may help in understanding the positioning of the SS and the safety of various transmastoid approaches.

Intradural Combined Transpetrosal Approach for Primary Pontine Hemorrhage

OBJECTIVE

The standard combined transpetrosal approach (CTPA) is fundamentally an epidural approach that has been quite successfully practiced for many decades. However, it has some disadvantages, such as cosmetic problems, difficulties with custom-tailored petrosectomy, and cerebrospinal fluid leakage, as it is a complicated epidural procedure. We describe here a case of primary pontine hemorrhage via intradural CTPA (iCTPA), which is a modified technique of CTPA and includes intradural anterior petrosectomy and partial posterior petrosectomy without mastoidectomy and skeletonization of the sigmoid sinus.

METHODS

A 63-year-old woman with primary pontine hemorrhage underwent surgery via iCTPA to improve postoperative functional outcomes. After the temporal craniotomy without mastoidectomy and skeletonization of the sigmoid sinus, Kawase's triangle and Trautmann's triangle were identified from the intradural space. Resection of Kawase's triangle and partial resection of Trautmann's triangle were performed to approach the frontotemporal surface of the pons. The hematoma was irrigated and totally removed after corticotomy on the pons.

RESULTS

The postoperative symptoms of the patient improved within 2 weeks without surgical complication.

CONCLUSIONS

The intradural approach allows for custom-tailored petrosectomy and is more straightforward than the epidural route, although it can injure the vein of Labbé. Moreover, it can also reduce cosmetic problems and cerebrospinal fluid leakage. iCTPA could provide enough working space for the frontolateral surface of pontine and petroclival lesions without the need for mastoidectomy and skeletonization of the sigmoid sinus.

Anatomical study of presigmoid-retrolabyrinthine approach based on temporal bone high-resolution CT

BACKGROUND

The surgical approach of acoustic neuroma includes translabyrinthine, transcranial fossa, suboccipital retrosigmoid sinus, and presigmoid retrolabyrinthine approach. Aims/Objective: To provide the anatomical basis for the surgical selection of presigmoid retrolabyrinthine approach by measuring the anatomical parameters of retrolabyrinthine space of the petrous bone by high-resolution CT.

MATERIAL AND METHODS

A retrospective study of 208 high-resolution CT (HRCT) images of 104 patients examined in our hospital were analyzed retrospectively. Forty-nine males and 55 females were included in this study. Lines were drawn on the HRCT to measure the morphological data for pre-operational assessment.

RESULT

Morphological data were retracted from HRCT, for preoperational assessment.

CONCLUSION AND SIGNIFICANCE

Using the standard postprocessing images of temporal bone HRCT can predict the size of the retrolabyrinthine space and the degree of exposure to the inner auditory canal, providing an important anatomical index for the choice of presigmoid retrolabyrinthine approach.

Morphological analysis of sigmoid sinus anatomy: clinical applications to neurotological surgery

OBJECTIVES

The primary objective of this study was to use high-resolution micro-CT images to create accurate three-dimensional (3D) models of several intratemporal structures, and to compare several surgically important dimensions within the temporal bone. The secondary objective was to create a statistical shape model (SSM) of a dominant and non-dominant sigmoid sinus (SS) to provide a template for automated segmentation algorithms.

METHODS

A free image processing software, 3D Slicer, was utilized to create three-dimensional reconstructions of the SS, jugular bulb (JB), facial nerve (FN), and external auditory canal (EAC) from micro-CT scans. The models were used to compare several clinically important dimensions between the dominant and non-dominant SS. Anatomic variability of the SS was also analyzed using SSMs generated using the Statismo software framework.

RESULTS

Three-dimensional models from 38 temporal bones were generated and analyzed. Right dominance was observed in 74% of the paired SSs. All distances were significantly shorter on the dominant side (p < 0.05), including: EAC - SS (dominant: 13.7 ± 3.4 mm; non-dominant: 15.3 ± 2.7 mm), FN - SS (dominant: 7.2 ± 1.8 mm; non-dominant: 8.1 ± 2.3 mm), 2nd genu FN - superior tip of JB (dominant: 8.7 ± 2.2 mm; non-dominant: 11.2 ± 2.6 mm), horizontal distance between the superior tip of JB - descending FN (dominant: 9.5 ± 2.3 mm; non-dominant: 13.2 ± 3.5 mm), and horizontal distance between the FN at the stylomastoid foramen - JB (dominant: 5.4 ± 2.2 mm; non-dominant: 7.7 ± 2.1). Analysis of the SSMs indicated that SS morphology is most variable at its junction with the transverse sinus, and least variable at the JB.

CONCLUSIONS

This is the first known study to investigate the anatomical variation and relationships of the SS using high resolution scans, 3D  models and statistical shape analysis. This analysis seeks to guide neurotological surgical approaches and provide a template for automated segmentation and surgical simulation.

Radiographic Assessment of the presigmoid retrolabyrinthine approach

Background:

Lesions of the petroclival fissure are difficult to access surgically. Both retrosigmoid and presigmoid retrolabyrinthine approaches have been described to successfully treat these complex tumors. The retrosigmoid approach offers quick and familiar access, whereas the presigmoid retrolabyrinthine approach reduces the operative distance and the need for cerebellar retraction. The presigmoid retrolabyrinthine approach, however, is constrained by anatomical limits that can be subject to patient variation. We sought to characterize the surgically relevant variation to guide preoperative assessment.

Methods:

One hundred and seventy-seven high-resolution computed tomography scans of the head (without preexisting pathology) were reviewed. Three hundred and fifty-four temporal bone scans were analyzed for level of aeration, size of Trautmann's triangle dura, and petrous slope. Petrous slope is the angle between the anterior sigmoid sinus and the petroclival fissure at the level of the internal acoustic canal.

Results:

Trautmann's triangle area had a mean of 185.15 mm² (range 71.4–426.7 mm²). Petrous slope had a mean value of 149° (range 106–178°). Increasing aeration was found to be correlated with decreasing petrous slope and decreasing Trautmann's triangle area.

Conclusion:

The presigmoid retrolabyrinthine approach is uniquely confined. Variations in temporal bone anatomy can have dramatic impacts on the operative time, risk profile, and final exposure. Preoperative assessment is critical in guiding the surgeon on the appropriateness of approach. Preoperative measurement of Trautmann's triangle, petrous slope, and aeration can help to reduce surgical morbidity.

The Retrolabyrinthine Presigmoid Approach to the Anterior Cerebellopontine Region: Expanding the Limits of Trautmann Triangle

OBJECTIVE

The anatomic area exposed through exposure of Trautmann triangle may not be sufficient. We studied the additional exposure provided by skeletonizing the sigmoid sinus (SS).

METHODS

In 5 human cadaveric heads, thin-cut computed tomography images of 2 sides of the temporal bone were obtained for a total of 10 sides. The estimated surgical working angle was calculated based on the relationship of the SS to the posterior semicircular canal (PSC), superior petrosal sinus, and jugular bulb on imaging. Mastoidectomy was performed, and heads with and without SS skeletonization were remeasured.

RESULTS

Working angle calculated on computed tomography was 56° ± 11.3. Skeletonization of the SS increased the distance between the PSC and SS by 5 mm (P = 0.01) and between the lateral semicircular canal and SS by 4 mm (P = 0.01). Skeletonization and retraction of the SS significantly increased the distance between the PSC and lateral semicircular canal to the SS. On images obtained after mastoidectomy, skeletonizing the SS helped improve anterior visibility on most samples that had an SS that was lateral to the PSC on axial imaging. In samples in which the SS was medial to the PSC or had only minimal lateral displacement, skeletonizing the SS did not markedly improve visibility of the retrolabyrinthine space.

CONCLUSIONS

Working area and visibility improved as the PSC and SS approached the same plane on axial imaging. Preoperative evaluation of the laterality of the SS to the PSC may assist a surgeon in determining the need for skeletonizing the SS and avoiding possible vascular injuries.