Skull Base Anatomy

The investigation of cranial fossae in the intracranial cavity of fixed cadaveric skull bases: associations with sex, laterality, and clinical significance

PURPOSE

Our study aims to investigate three parts of the intracranial cavity, their distances to essential anatomical landmarks, and the correlations between these distances with sex, laterality, and surgical significance.

METHODS

The cranial nerve foraminae and essential surgical landmarks of each fossa were investigated bilaterally in 30 adult formalin-fixed cadaveric heads. Measurements, including lengths, depths, diameters, and horizontal distances to each other, to the midline of the skull, and to the outer lateral margin of the skull, were recorded on both sides.

RESULTS

The optic canal (OC) depth, internal auditory meatus (IAM) width, CNVII and CNIX diameters, and accessory hypoglossal canal (HC) distance were significantly greater on the left side (p < 0.05). CNVI length, CNV diameter, CNXI length, and the distances of the HC and accessory HC from the skull were significantly greater on the right side (p < 0.05). In males, correlations were found between the length of the left CNVIII and the right IAM diameter (r = 0.864, p = 0.001), right CNVIII length (r = 0.709, p = 0.022), right accessory HC length (r = 0.847, p = 0.016), and right-sided skull distance (r = 0.829, p = 0.042). In females, correlations were noted between IAM depth and length, right IAM location relative to the skull, left CNIX and CNX lengths, left CNXII length, left accessory HC location relative to the skull, and accessory HC length.

CONCLUSIONS

The findings of the current study indicate inherent asymmetry, sexual dimorphism, and variability in certain cranial nerves among cadaveric heads, which could have implications for surgical procedures, neuroanatomical studies, and clinical assessments. The study revealed side disparities and correlations within cranial fossa formations and essential surgical landmarks in both genders.

PitSurgRT: real-time localization of critical anatomical structures in endoscopic pituitary surgery

PURPOSE

Endoscopic pituitary surgery entails navigating through the nasal cavity and sphenoid sinus to access the sella using an endoscope. This procedure is intricate due to the proximity of crucial anatomical structures (e.g. carotid arteries and optic nerves) to pituitary tumours, and any unintended damage can lead to severe complications including blindness and death. Intraoperative guidance during this surgery could support improved localization of the critical structures leading to reducing the risk of complications.

METHODS

A deep learning network PitSurgRT is proposed for real-time localization of critical structures in endoscopic pituitary surgery. The network uses high-resolution net (HRNet) as a backbone with a multi-head for jointly localizing critical anatomical structures while segmenting larger structures simultaneously. Moreover, the trained model is optimized and accelerated by using TensorRT. Finally, the model predictions are shown to neurosurgeons, to test their guidance capabilities.

RESULTS

Compared with the state-of-the-art method, our model significantly reduces the mean error in landmark detection of the critical structures from 138.76 to 54.40 pixels in a 1280 × 720-pixel image. Furthermore, the semantic segmentation of the most critical structure, sella, is improved by 4.39% IoU. The inference speed of the accelerated model achieves 298 frames per second with floating-point-16 precision. In the study of 15 neurosurgeons, 88.67% of predictions are considered accurate enough for real-time guidance.

CONCLUSION

The results from the quantitative evaluation, real-time acceleration, and neurosurgeon study demonstrate the proposed method is highly promising in providing real-time intraoperative guidance of the critical anatomical structures in endoscopic pituitary surgery.

Comparing the Clinical Orientation Benefits of Endoscopic demonstration on the Nose, Paranasal Sinuses, and Skull Base Versus Cadaveric Dissection for First-Year Medical Undergraduates

The study aims to evaluate the advantages of using endoscopic demonstrations to teach nose, paranasal sinuses, and skull base anatomy compared to traditional cadaveric demonstrations. Traditional dissection methods do not provide an accurate representation of in vivo visualization of these anatomical areas. The goal is to align the teaching approach with the perspective students will have during clinical practice for better clinical orientation. In this study, 100 first-year medical students were split into two groups: Group A and Group B, each with 50 students. Group A received teaching through endoscopic demonstrations, while Group B had cadaveric demonstrations, both focused on nose, paranasal sinuses, and skull base anatomy. To assess comprehension and clinical orientation, both groups completed a questionnaire with clinically relevant questions, and their responses were collected and compared for analysis. Students who received endoscopic training showed better accuracy in addressing clinical queries than those only exposed to cadaveric dissection. Many participants favored incorporating endoscopic instruction, either as a replacement or addition to traditional cadaveric dissection, for the studied topics. The endoscopically trained group performed better in understanding anatomical landmarks, mentally reconstructing 3D images, and conceptualizing surgical approaches for the targeted anatomical areas. Incorporating endoscopic training for the nasal cavity, paranasal sinuses and skull base into the undergraduate medical curriculum would substantially augment students' clinical understanding and provide a more profound grasp of the dynamic anatomy in these areas.

Usefulness of Opening the Diaphragma Sellae Before Transecting Interclinoidal Ligament for Endoscopic Endonasal Transoculomotor Triangle Approach: Technical Nuances and Surgical Outcomes

OBJECTIVE

Opening the oculomotor triangle (OT) and removing the posterior fossa lesion by endoscopic endonasal approach (EEA) is challenging for even an experienced endoscopic neurosurgeon. We summarize the treatment experience and technical nuances with EEA for resection of pituitary neuroendocrine tumors and cavernous sinus (CS) meningiomas invading through the OT.

METHODS

Between 2018 and 2022, 8 patients, comprising 5 with pituitary neuroendocrine tumors (3 with nonfunctioning and 2 with somatotroph tumors with increased levels of growth hormone) and 3 CS meningiomas, were treated using an endoscopic endonasal transoculomotor triangle approach. The critical surgical technique is continuously opening the diaphragma sellae from medial to lateral toward the interclinoidal ligament and transecting it to enlarge the OT. We evaluated preoperative tumor size, previous surgical history, preoperative symptoms, extent of tumor resection, histopathology, and postoperative complications for all patients.

RESULTS

The gross total resection (defined as complete removal) in 3 patients (38%), near-total resection (defined as >95% removal) in 4 patients (50%), and subtotal resection (defined as ≤90% removal) in 1 patient (12%) and gross total resection of tumor invading through the OT was achieved in all patients through pure EEA. Two of 3 patients with visual deficits in nonfunctioning pituitary neuroendocrine tumors improved, and the other remained stable postoperatively. One patient showed transient oculomotor nerve palsy. The growth hormone level of the 2 patients with somatotroph tumors declined to normal. For 3 patients with CS meningiomas, cranial nerve palsy improved in 2 patients, whereas the other patient developed increased facial numbness after surgery.

CONCLUSIONS

The endoscopic endonasal transoculomotor triangle approach is an efficient surgical option for tumors with CS invasion and OT penetration.

Interdisciplinary Management of Skull Base Tumors

OBJECTIVE

Endoscopic endonasal skull base surgery has gained acceptance worldwide. Comparative analysis has demonstrated that endoscopic skull base surgery may have advantages for many pathologies of the anterior skull base, e. g., sinonasal malignant tumors; pathologies of the central skull base, e. g., pituitary adenomas, craniopharyngiomas; well-selected cases of planum sphenoidale and tuberculum sellae meningiomas; or for clival lesions, e. g., chordomas, chondrosarcomas, or selected meningiomas. Over the past three decades, interdisciplinary surgical teams, consisting of otolaryngologists and neurosurgeons, have provided detailed anatomical knowledge, suggested new approaches or modifications of established surgical techniques, and offered continued surgical education.

METHOD

A review of pertinent literature was conducted with an emphasis on interdisciplinary endoscopic surgery of skull base lesions.

RESULTS

Based on the authors̓ surgical experience in two different interdisciplinary endoscopic skull base centers, the authors classify approaches for endoscopic endonasal skull base surgery, describe indications, and key anatomic landmarks for common pathologies, and highlight surgical techniques to avoid complications.

CONCLUSION

Interdisciplinary endonasal endoscopic surgery combines surgical expertise, improves resection rates for many pathologies, and minimizes morbidity by reducing the incidence of surgical complications.

Survey of Skull Base Surgeons' Approach to Carcinomas Involving the Cavernous Sinus

Objectives  Carcinomas involving the cavernous sinus are challenging to resect without compromising important neurovascular structures. Given the morbidity and mortality of these operations, radiotherapy, chemotherapy, and immunotherapy are more often utilized. Although limited to case reports and small series, radical resection of the cavernous sinus has been proposed. We aimed to study surgeons' willingness to perform cavernous sinus exenteration (CSE) under different clinical scenarios. Design, Setting, Participants, Main Outcome Measures  We conducted an online survey from April to July 2021 among members of the Skull Base Congress and the North American Skull Base Society. Descriptive statistics were used to analyze the main outcome measure of willingness to perform CSE . Results  The analytic sample ( n  = 112) included 54% otolaryngologists and 43% neurosurgeons. Eighty-six percent practiced in an academic setting. Surgeons' willingness to perform CSE was low (6-16% under different clinical scenarios), citing a belief that they could not obtain oncologic margins and the procedure's morbidity. Forty-five percent had at least one patient undergo CSE with 72% of patients surviving no more than 2 years. Complications included chronic intractable pain, cerebrospinal fluid leak, cerebrovascular accident, and/or intraoperative/postoperative death within 30 days. Sixty percent agreed that the availability of immunotherapy and genomic sequencing has affected their willingness to offer CSE. Conclusion  Overall, most of the surgeons surveyed were unwilling to offer CSE for carcinomatous cavernous sinus invasion, whether for primary disease or recurrence. Given the rarity of these tumors and the limited data on CSE, these results may provide more information for clinicians and patients for these treatment decisions.

Physiological 68Ga-PSMA-11 Uptake in Dural Venous Sinuses

ABSTRACT

We describe hitherto unreported physiological low-grade 68Ga-PSMA-11 uptake in dural sinuses of patients who underwent 68Ga-PSMA-11 PET/CT for evaluation of prostate carcinoma. A strong positive correlation was found between SUVmax of tracer uptake in dural sinuses and SUVmax of blood pool activity in superior vena cava. Low-grade 68Ga-PSMA-11 uptake seen in dural sinuses is physiological and is most likely result of venous blood pool activity. Such uptake should not be interpreted as pathological. Knowledge of such physiological uptake is essential for optimal interpretation of PSMA PET/CT images and differentiating physiological versus pathological uptake.

Frontiers of Cranial Base Surgery: Integrating Technique, Technology, and Teamwork for the Future of Neurosurgery

The landscape of cranial base surgery has undergone monumental transformations over the past several decades. This article serves as a comprehensive survey, detailing both the historical and current techniques and technologies that have propelled this field into an era of unprecedented capabilities and sophistication. In the prologue, we traverse the historical evolution from rudimentary interventions to the state-of-the-art neurosurgical methodologies that define today's practice. Subsequent sections delve into the anatomical complexities of the anterior, middle, and posterior cranial fossa, shedding light on the intricacies that dictate surgical approaches. In a section dedicated to advanced techniques and modalities, we explore cutting-edge evolutions in minimally invasive procedures, pituitary surgery, and cranial base reconstruction. Here, we highlight the seamless integration of endocrinology, biomaterial science, and engineering into neurosurgical craftsmanship. The article emphasizes the paradigm shift towards "Functionally" Guided Surgery facilitated by intraoperative neuromonitoring. We explore its historical origins, current technologies, and its invaluable role in tailoring surgical interventions across diverse pathologies. Additionally, the digital era's contributions to cranial base surgery are examined. This includes breakthroughs in endoscopic technology, robotics, augmented reality, and the potential of machine learning and AI-assisted diagnostic and surgical planning. The discussion extends to radiosurgery and radiotherapy, focusing on the harmonization of precision and efficacy through advanced modalities such as Gamma Knife and CyberKnife. The article also evaluates newer protocols that optimize tumor control while preserving neural structures. In acknowledging the holistic nature of cranial base surgery, we advocate for an interdisciplinary approach. The ecosystem of this surgical field is presented as an amalgamation of various medical disciplines, including neurology, radiology, oncology, and rehabilitation, and is further enriched by insights from patient narratives and quality-of-life metrics. The epilogue contemplates future challenges and opportunities, pinpointing potential breakthroughs in stem cell research, regenerative medicine, and genomic tailoring. Ultimately, the article reaffirms the ethos of continuous learning, global collaboration, and patient-first principles, projecting an optimistic trajectory for the field of cranial base surgery in the coming decade.

Surgical Anatomy and Approaches of the Anterior Cranial Fossa from a Transcranial and Endonasal Perspective

The anterior cranial fossa (ACF) is a complex anatomical region that can be affected by a broad spectrum of pathology. For the surgical treatment of these lesions, many approaches have been described, each of them with different scope and potential surgical complications, often associated with significant morbidity. Traditionally, tumors involving the ACF have been operated by transcranial approaches; however, in the last two decades, endoscopic endonasal approaches (EEAs) have been gaining popularity. In this work, the authors review and describe the anatomical aspects of the ACF and the technical nuances of transcranial and endoscopic approaches for tumors located in this region. Four approaches were performed in embalmed cadaveric specimens and the key steps were documented. Four illustrative cases of ACF tumors were selected to demonstrate the clinical application of anatomical and technical knowledge, which are essential in the preoperative decision-making process.

Microsurgical anatomy and the importance of the petrosal process of the sphenoid bone in endonasal surgery

OBJECTIVE

The petrosal process of the sphenoid bone (PPsb) is a relevant skull base osseous prominence present bilaterally that can be used as a key surgical landmark, especially for identifying the abducens nerve. The authors investigated the surgical anatomy of the PPsb, its relationship with adjacent neurovascular structures, and its practical application in endoscopic endonasal surgery.

METHODS

Twenty-one dried skulls were used to analyze the osseous anatomy of the PPsb. A total of 16 fixed silicone-injected postmortem heads were used to expose the PPsb through both endonasal and transcranial approaches. Dimensions and distances of the PPsb from the foramen lacerum (inferiorly) and top of the posterior clinoid process (PCP; superiorly) were measured. Moreover, anatomical variations and the relationship of the PPsb with the surrounding crucial structures were recorded. Three representative cases were selected to illustrate the clinical applications of the findings.

RESULTS

The PPsb presented as a triangular bony prominence, with its base medially adjacent to the dorsum sellae and its apex pointing posterolaterally toward the petrous apex. The mean width of the PPsb was 3.5 ± 1 mm, and the mean distances from the PPsb to the foramen lacerum and the PCP were 5 ± 1 and 11 ± 2.5 mm, respectively. The PPsb is anterior to the petroclival venous confluence, superomedial to the inferior petrosal sinus, and inferomedial to the superior petrosal sinus; constitutes the inferomedial limit of the cavernous sinus; and delimits the upper limit of the paraclival internal carotid artery (ICA) before the artery enters the cavernous sinus. The PPsb is anterior and medial to and below the sixth cranial nerve, forming the floor of Dorello's canal. During surgery, gentle mobilization of the paraclival ICA reveals the petrosal process, serving as an accurate landmark for the location of the abducens nerve.

CONCLUSIONS

This investigation revealed details of the microsurgical anatomy of the PPsb, its anatomical relationships, and its application as a surgical landmark for identifying the abducens nerve. This novel landmark may help in minimizing the risk of abducens nerve injury during transclival approaches, which extend laterally toward the petrous apex and cavernous sinus region.

Stereotactic Radiosurgery for Benign Cavernous Sinus Meningiomas: A Multicentre Study and Review of the Literature

Simple Summary

Meningiomas are the most common tumours of the central nervous system (CNS). Despite their benign histology, proximity to critical neurovascular structures may lead to significant morbidity with tumour growth. This is the case for cavernous sinus meningiomas (CSMs), as their growth may surround critical neuro-vascular structures and cause significant morbidity. Radical microsurgical resection carries a high risk of additional neurological deficits, as well as the risk of death. Current management of these tumours, where treatment is indicated, has moved away from radical surgery towards radiotherapy/radiosurgery. This is particularly the case for patients who have residual or recurring tumours after previous surgery. There are many reports that describe the effectiveness of using stereotactic radiosurgery (SRS) for CSMs; however, large cohort analyses are lacking. This multicentre analysis reports the outcome data of over 1000 patients with CSMs who were treated with SRS. SRS shows a high local tumour control rate with few complications. These results agree with previous reports in the literature. SRS is a valuable primary or adjuvant treatment option for CSMs.

Abstract

Cavernous sinus meningiomas (CSMs) remain a surgical challenge due to the intimate involvement of their contained nerves and blood vessels. Stereotactic radiosurgery (SRS) is a safe and effective minimally invasive alternative for the treatment of small- to medium-sized CSMs. Objective: To assess the medium- to long-term outcomes of SRS for CSMs with respect to tumour growth, prevention of further neurological deterioration and improvement of existing neurological deficits. This multicentric study included data from 15 European institutions. We performed a retrospective observational analysis of 1222 consecutive patients harbouring 1272 benign CSMs. All were treated with Gamma Knife stereotactic radiosurgery (SRS). Clinical and imaging data were retrieved from each centre and entered into a common database. All tumours with imaging follow-up of less than 24 months were excluded. Detailed results from 945 meningiomas (86%) were then analysed. Clinical neurological outcomes were available for 1042 patients (85%). Median imaging follow-up was 67 months (mean 73.4, range 24–233). Median tumour volume was 6.2 cc (+/−7), and the median marginal dose was 14 Gy (+/−3). The post-treatment tumour volume decreased in 549 (58.1%), remained stable in 336 (35.6%) and increased in only 60 lesions (6.3%), yielding a local tumour control rate of 93.7%. Only 27 (2.8%) of the 60 enlarging tumours required further treatment. Five- and ten-year actuarial progression-free survival (PFS) rates were 96.7% and 90.1%, respectively. Tumour control rates were higher for women than men (p = 0.0031), and also for solitary sporadic meningiomas (p = 0.0201). There was no statistically significant difference in outcome for imaging-defined meningiomas when compared with histologically proven WHO Grade-I meningiomas (p = 0.1212). Median clinical follow up was 61 months (mean 64, range 6–233). Permanent morbidity occurred in 5.9% of cases at last follow-up. Stereotactic radiosurgery is a safe and effective method for treating benign CSM in the medium term to long term.

Development of 3-dimensional printed simulation surgical training models for endoscopic endonasal and transorbital surgery

Background

Endoscopic skull base surgery (ESBS) is complex, requiring methodical and unremitting surgical training. Herein, we describe the development and evaluation of a novel three-dimensional (3D) printed simulation model for ESBS. We further validate the efficacy of this model as educational support in neurosurgical training.

Methods

A patient-specific 3D printed simulation model using living human imaging data was established and evaluated in a task-based hands-on dissection program. Endoscopic endonasal and transorbital procedures were simulated on the model by neurosurgeons and otorhinolaryngology surgeons of varying experience. All procedures were recorded using a high-definition camera coupled with digital video recorder system. The participants were asked to complete a post-procedure questionnaire to validate the efficacy of the model.

Results

Fourteen experts and 22 trainees participated in simulations, and the 32 participants completed the post-procedure survey. The anatomical realism was scored as 4.0/5.0. The participants rated the model as helpful in hand-eye coordination training (4.7/5.0) and improving surgical skills (4.6/5.0) for ESBS. All participants believed that the model was useful as educational support for trainees (4.7 [ ± 0.5]). However, the color (3.6/5.0) and soft tissue feedback parameters (2.8/5) scored low.

Conclusion

This study shows that high-resolution 3D printed skull base models for ESBS can be generated with high anatomical accuracy and acceptable haptic feedback. The simulation program of ESBS using this model may be supplemental or provide an alternative training platform to cadaveric dissection.

A practical overview of CT and MRI features of developmental, inflammatory, and neoplastic lesions of the sphenoid body and clivus

The sphenoid bone is an unpaired bone that contributes to the formation of the skull base. Despite the enormous progress in transnasal endoscopic visualisation, imaging techniques remain the cornerstones to characterise any pathological condition arising in this area. In the present review, we offer a bird’s-eye view of the developmental, inflammatory, and neoplastic alterations affecting the sphenoid body and clivus, with the aim to propose a practical diagnostic aid for radiologists based on clinico-epidemiological, computed tomography, and magnetic resonance imaging features.

Augmented Reality in Neurosurgery, State of Art and Future Projections. A Systematic Review

Background

The use of augmented reality (AR) is growing in medical education, in particular, in radiology and surgery. AR has the potential to become a strategic component of neurosurgical training courses. In fact, over the years, there has been a progressive increase in the application of AR in the various fields of neurosurgery. In this study, the authors aim to define the diffusion of these augmented reality systems in recent years. This study describes future trends in augmented reality for neurosurgeons.

Methods

A systematic review of the literature was conducted to identify research published from December 1st, 2011 to November 30th, 2021. Electronic databases (PubMed, PubMed Central, and Scopus) were screened. The methodological quality of studies and extracted data were assessed for “augmented reality” and “neurosurgery”. The data analysis focused on the geographical distribution, temporal evolution, and topic of augmented reality in neurosurgery.

Results

A total of 198 studies have been included. The number of augmented reality applications in the neurosurgical field has increased during the last 10 years. The main topics on which it is mostly applied are spine surgery, neuronavigation, and education. The geographical distribution shows extensive use of augmented reality in the USA, Germany, China, and Canada. North America is the continent that uses augmented reality the most in the training and education of medical students, residents, and surgeons, besides giving the greatest research contribution in spine surgery, brain oncology, and surgical planning. AR is also extensively used in Asia for intraoperative navigation. Nevertheless, augmented reality is still far from reaching Africa and other countries with limited facilities, as no publications could be retrieved from our search.

Conclusions

The use of AR is significantly increased in the last 10 years. Nowadays it is mainly used in spine surgery and for neurosurgical education, especially in North America, Europe and China. A continuous growth, also in other aspects of the specialty, is expected in the next future.

Current Management and Image Review of Skull Base Chordoma: What the Radiologist Needs to Know

Chordomas of the skull-base are typically slow-growing, notochord-derived tumors that most commonly originate along the clivus. Skull base chordoma is treated with surgery and radiotherapy. Local recurrence approaches 50% at 10 years. Radiologists play a critical role in diagnosis, treatment planning, and follow-up. Surgeons and radiation oncologists rely on radiologists for pre-operative delineation of tumor and adjacent anatomy, identification of post-treatment changes and disease recurrence, and radiation treatment effects. This review provides an overview of clinical characteristics, surgical anatomy, indications for radiotherapy, identification of treatment complications, and patterns of disease recurrence for radiologists to provide value in the management of these lesions.

Classification of Pituitary Adenomas Invading the Cavernous Sinus Assisted by Three-Dimensional Multimodal Imaging and Its Clinical Application

Introduction  To help diagnose and evaluate the prognosis of pituitary adenoma with cavernous sinus (CS) invasion and guide endonasal endoscopic surgery (EES) assisted by intraoperative navigation (ION) with three-dimensional multimodal imaging (3D-MMI). We propose a classification of CS invasion based on 3D-MMI. Methods  We picked some appropriate cases and reconstructed the 3D-MMI and then classified them into 3 grades according to the stereo relationship among ICA, tumor and CS in 3D-MMI. Then, we applied different strategies according to their grade to remove pituitary adenomas that invaded the CS. Results  All 38 patients were divided into 3 grades. Tumors compressing the ICA and CS without CS invasion were divided into grade 1. Tumors encasing the ICA and invading the superior-posterior compartment and/or anterior-inferior compartment but without distinct separation of the ICA and CS lateral wall were deemed as grade 2. Tumors encasing the ICA and filling the lateral compartment of the CS that dissociated the lateral wall from the ICA were deemed as grade 3. The 3D-MMI enabled adequate spatial visualization of the ICA, CS and tumors. All patients were operated on under the guidance of ION with 3D-MMI. Conclusion  Classification based on 3D-MMI can better demonstrate the relationships among tumor, ICA and CS in a stereo and multi-angle view, which will have significance in guiding the surgical strategy.

Invasive Corridor of Clivus Extension in Pituitary Adenoma: Bony Anatomic Consideration, Surgical Outcome and Technical Nuances

Background

It is well known that the clivus is composed of abundant cancellous bone and is often invaded by pituitary adenoma (PA), but the range of these cancellous bone corridors is unknown. In addition, we found that PA with clivus invasion is sometimes accompanied by petrous apex invasion, so we speculated that the petrous apex tumor originated from the clivus cancellous bone corridor. The aim of this study was to test this hypothesis by investigating the bony anatomy associated with PA with clival invasion and its clinical significance.

Methods

Twenty-two cadaveric heads were used in the anatomical study to research the bony architecture of the clivus and petrous apex, including six injected specimens for microsurgical dissection and sixteen cadavers for epoxy sheet plastination. The surgical videos and outcomes of PA with clival invasion in our single center were also retrospectively reviewed.

Results

The hypoglossal canal and internal acoustic meatus are composed of bone canals surrounded by cortical bone. The cancellous corridor within clivus starts from the sellar or sphenoid sinus floor and extends downward, bypassing the hypoglossal canal and finally reaching the occipital condyle and the medial edge of the jugular foramen. Interestingly, we found that the cancellous bone of the clivus was connected with that of the petrous apex through petroclival fissure extending to the medial margin of the internal acoustic meatus instead of a separating cortical bone between them as it should be. It is satisfactory that the anatomical outcomes of the cancellous corridor and the path of PA with clival invasion observed intraoperatively are completely consistent. In the retrospective cohort of 49 PA patients, the clival component was completely resected in 44 (89.8%), and only five (10.2%) patients in the early-stage had partial residual cases in the inferior clivus.

Conclusion

The petrous apex invasion of PA is caused by the tumor invading the clivus and crossing the petroclival fissure along the cancellous bone corridor. PA invade the clivus along the cancellous bone corridor and can also cross the hypoglossal canal to the occipital condyle. This clival invasion pattern presented here deepens our understanding of the invasive characteristics of PA.

The "STARS-CT-MADE" Study: Advanced Rehearsal and Intraoperative Navigation for Skull Base Tumors

BACKGROUND

Skull base meningiomas represent a challenge for neurosurgeons, and the procedures are typically performed by experienced neurosurgeons, thus limiting resident training. A new simulation and rehearsal device can be used as an aid for senior surgeons during these operations and serve as a training tool for junior surgeons.

METHODS

Forty patients harboring an anterior/middle fossa meningioma were recruited. Surgical Theater, a rehearsal/simulation platform, was used for preoperative planning and intraoperative 3D navigation on 20 patients (CT-MADE group), while the remaining (control group) underwent a traditional navigation. Qualitative comparisons between the 2 groups were made with regard to surgical procedure and patient outcome. Satisfaction questionnaires were completed by expert neurosurgeons and residents to assess the overall usefulness of the platform. Furthermore, the surface of the simulated craniotomy performed during the planning was compared with the one actually performed during surgery in order to evaluate the reliability of the planning.

RESULTS

No differences between the 2 groups were found (surgery duration: P = 0.4; visual impairment: P = 0.56). Both residents and senior neurosurgeons enjoyed using the platform for intraoperative navigation and planning; simulated craniotomies were significantly smaller as compared with the real ones (P = 0.009), probably because it was not intuitive to depict the exact margins of the operculum with the platform.

CONCLUSION

Surgical Theater helped residents to improve their anatomic and procedural comprehension and was deemed as a useful aid to safely perform some demanding neurosurgical procedures, by both senior and junior surgeons.

Changes of Peripapillary Region Perfusion in Patients with Chiasmal Compression Caused by Sellar Region Mass

Purpose

To evaluate the peripapillary vessel density (pVD) and the peripapillary nerve fiber layer (pRNFL) thickness in patients with chiasmal compression caused by sellar region mass using optical coherence tomography angiography (OCTA).

Methods

This is an observational, cross-sectional study of 31 patients (31 eyes) with chiasmal compression caused by sellar region mass and 34 healthy controls (34 eyes). Automated perimetry and OCTA were performed. The pVD and pRNFL thickness were compared between the two groups. The impact of tumor diameter, duration of symptoms, and cavernous sinus (CS) invasion on visual dysfunction, pVD, and pRNFL thickness was also analyzed. Furthermore, we divided the patients into two subgroups according to whether there was an absolute defect in the central visual field and evaluated their pVD and pRNFL thickness, respectively.

Results

Compared to the healthy control group, there was a statistically significant decrease in pVD and pRNFL thickness in patients with chiasmal compression (p < 0.05), especially in patients with substantial absolute defects in the central visual field. Tumor diameter, duration of symptoms, and CS invasion did not appear to be associated with pVD and pRNFL thickness. There was a significant positive correlation between the pVD and pRNFL thickness in patients with chiasmal compression (p < 0.001).

Conclusion

pVD and pRNFL thickness are significantly decreased in patients with chiasmal compression revealed by OCTA, especially in patients with more severe visual field defects. A significant correlation between pVD and pRNFL thickness was demonstrated, which provides a clue for the study of the mechanism of changes in retinal perfusion in compressive optic neuropathy. It requires considerable attention that OCTA may play an important role in disease monitoring of sellar region mass. Hence, further studies are needed to verify whether OCTA is helpful to predict the prognosis of visual function after decompression surgery.

Transorbital endoscopic approaches to the skull base: a systematic literature review and anatomical description

Transorbital endoscopic approaches are increasing in popularity as they provide corridors to reach various areas of the ventral skull base through the orbit. They can be used either alone or in combination with different approaches when dealing with the pathologies of the skull base. The objective of the current study is to evaluate the surgical anatomy of transorbital endoscopic approaches by cadaver dissections as well as providing objective clinical data on their actual employment and morbidity through a systematic review of the current literature. Four cadaveric specimens were dissected, and step-by-step dissection of each endoscopic transorbital approach was performed to identify the main anatomic landmarks and corridors. A systematic review with pooled analysis of the current literature from January 2000 to April 2020 was performed and the related studies were analyzed. Main anatomical landmarks are presented based on the anatomical study and systematic review of the literature. With emphasis on the specific transorbital approach used, indications, surgical technique, and complications are reviewed through the systematic review of 42 studies (19 in vivo and 23 anatomical dissections) including 193 patients. In conclusion, transorbital endoscopic approaches are promising and appear as feasible techniques for the surgical treatment of skull base lesions. Surgical anatomy of transorbital endoscopic approaches can be mastered through knowledge of a number of anatomical landmarks. Based on data available in the literature, transorbital endoscopic approaches represent an important complementary that should be included in the armamentarium of a skull base team.

A novel diagnostic tool for the evaluation of hypothalamic-pituitary region and diagnosis of growth hormone deficiency: pons ratio

Backgrounds Limitations in the evaluation of the pituitary size and changes according to pubertal status make its validity questionable. Recently, in a small-scale study, pons ratio (PR) has been suggested as a more sensitive tool for diagnosis and etiological evaluation of growth hormone deficiency (GHD). The aim of the study is to evaluate the diagnostic value of PR in the diagnosis of GHD. Methods We retrospectively evaluated the pituitary magnetic resonance imaging (MRI) of 133 patients with a diagnosis of GHD. Primary axis (PA) was assigned as a line crossing the mid-sagittal dorsum sella and fourth ventricle. PR was defined as the pons height above the PA divided by total pons height. The PR of patients with GHD was compared to subjects without GHD. Results Study included 133 patients with GHD and 47 controls. In total, 121 (91%) patients had isolated GHD and 12 (9%) patients had multiple pituitary hormone deficiency. The PR of the patient group (mean: 0.32 ± 0.89; range: 0.14-0.63) was significantly higher than controls (mean: 0.26 ± 0.067; range 0.19-0.44) (p: 0.000). The optimal cut-off value of PR for GHD diagnosis was 0.27 (sensitivity 71% specificity 56%). There was a negative correlation between anterior pituitary height (APH)-SDS and PR (p: 0.002; r: -0.27). APH was increased, but PR remained unchanged in pubertal patients (p: 0.089). Conclusions PR measurement is a noninvasive, practical method with a cost-benefit clinical value. As it is not affected by pubertal status, PR is potentially a more sensitive tool for evaluation of pituitary gland in GHD patients compared to APH.

Perioperative olfactory dysfunction in patients with meningiomas of the anteromedial skull base

Olfactory dysfunction represents a main symptom in olfactory groove meningiomas (OGM). Besides this, olfactory function has been sparsely investigated in patients suffering from supratentorial meningiomas. Here, the authors explore pre- and postoperative variables associated with olfactory dysfunction in supratentorial meningioma patients. This is a retrospective study on supratentorial meningioma patients who underwent meningioma resection between January 2015 and January 2016. Preoperative and postoperative olfactory performance was quantified using a lateralized sniffin' stick odor identification test. Meningiomas affecting the olfactory system (n = 23) were compared to meningiomas in other locations among the control group (n = 40). Meningiomas that affected the olfactory system had odds of 3.6 and 3.7 in being associated with ipsilateral (lesional) and bilateral anosmia, respectively. Subgroup analysis revealed that meningiomas causing a midline shift across the frontal base and older age represented risk factors for preoperative anosmia. The odds of experiencing acquired postoperative ipsilateral anosmia were significantly increased in olfactory system affecting meningiomas (OR 11.1). Subgroup analysis highlighted OGMs to represent the predominant location associated with deterioration. General surgical complications predisposed patients to loss of contralateral (OR 12.3) and bilateral olfactory function (OR 27.8). Older age and meningiomas causing a midline shift across the frontal base predispose patients to preoperative olfactory dysfunction. Resection of OGMs and surgical complications are risk factors for postoperative olfactory deterioration to anosmia. Likely, olfactory dysfunction is underrecognized even in OGMs. In OGM surgery, however, preoperative lateralized testing might be critical to selecting an appropriate surgical route to preserve olfactory function. Clin. Anat. 32:524-533, 2019. © 2019 Wiley Periodicals, Inc.

Utility of first positron emission tomography-computed tomography scan as a prognostic tool following treatment of sinonasal and skull base malignancies

BACKGROUND

The prognostic value of the first posttreatment whole body integrated positron emission tomography-computed tomography (PET/CT) scanning in patients with sinonasal/skull base malignancies is undetermined.

METHODS

We retrospectively reviewed the data of all patients that underwent surgery for sinonasal/skull base malignancies in 2000-2015. The results of the pretreatment and posttreatment PET/CT findings and the clinical course were retrieved.

RESULTS

Thirty-eight patients (average age 60.6 years, 20 males) were included. Sensitivity and specificity, positive predictive value, and negative predictive value of the first PET/CT scan for predicting persistent/recurrent disease were 85.7%, 87.5%, 80%, and 91.3%, respectively. Overall 5-year survival was significantly lower in the first posttreatment PET/CT-positive group (35%) compared to the PET/CT-negative group (93%) (P = .0008).

CONCLUSION

Posttreatment PET/CT findings are highly prognostic in patients with sinonasal/skull base malignancies. Negative findings on the first posttreatment PET/CT scan predict a significantly better overall survival.

Anatomic Considerations for Sinonasal and Ventral Skull Base Malignancy

Malignancies of the sinonasal region and ventral skull base include a varied group of uncommon tumors that are a challenge to treat. These malignancies, with few exceptions, often present late because of their insidious growth and bland symptomatology. As with malignancies of other sites, the primary goal in surgical management is complete resection with negative margins. This presents a unique surgical challenge in that these lesions lie within a region of densely populated anatomic real estate. This fact reinforces the importance of complete preoperative work-up and a sound anatomic understanding. This article discusses key anatomic regions and their importance from an endonasal perspective.

Sellar and Parasellar Imaging

The skull base is a complex anatomical region that harbors many important neurovascular structures in a relatively confined space. The pathology that can develop at this site is varied, and many disease processes may present with similar clinical and neuroimaging findings. While computed tomography maintains a role in the evaluation of many entities and can, for instance, delineate osseous erosion with great detail and characterize calcified tumor matrices, magnetic resonance imaging (MRI) is the mainstay in the neuroimaging assessment of most pathology occurring at the skull base. Various MRI sequences have proven to be robust tools for tissue characterization and can provide information on the presence of lipids, paramagnetic and diamagnetic elements, and tumor cellularity, among others. In addition, currently available MRI techniques are able to generate high spatial resolution images that allow visualization of cranial nerves and their involvement by adjacent pathology. The information obtained from such examinations may aid in the distinction of these disease processes and in the accurate delineation of their extent prior to biopsy or treatment planning.