Open-door extended endoscopic transorbital technique to the paramedian anterior and middle cranial fossae: technical notes, anatomomorphometric quantitative analysis, and illustrative case.

OBJECTIVE: The superior eyelid endoscopic transorbital approach (SETOA) provides a direct and short minimally invasive route to the anterior and middle skull base. Nevertheless, it uses a narrow corridor that limits its angles of attack. The aim of this study was to evaluate the feasibility and potential benefits of an "extended" conservative variant of the "standard" endoscopic transorbital approach-termed "open-door"-to enhance the exposure of lesions affecting the paramedian aspect of the anterior and middle cranial fossae. METHODS: First, the authors described the technical nuances of the open-door extended transorbital approach (ODETA). Next, they documented its morphometric advantages over standard SETOA. Finally, they provided a clinical-anatomical application to demonstrate enhanced exposure and better angles of attack to treat lesions occupying the paramedian anterior and middle cranial fossae. Five adult cadaveric specimens (10 sides) initially underwent standard SETOA and then extended open-door SETOA (ODETA to the paramedian anterior and middle fossae). The adjunct of hinge-orbitotomy, through three surgical steps and straddling the frontozygomatic suture, converted conventional SETOA to its extended open-door variant. CT scans were performed before dissection and uploaded to the neuronavigation system for quantitative analysis. The angles of attack on the axial plane that addressed four key landmarks, namely the tip of the anterior clinoid process (ACP), foramen rotundum (FR), foramen ovale (FO), and trigeminal impression (TI), were calculated for both operative techniques and compared. RESULTS: Hinge-orbitotomy of the extended open-door SETOA resulted in several surgical, functional, and esthetic advantages: it provided wider axial angles of attack for each of the target points, with a gain angle of 26.68° ± 1.31° for addressing the ACP (p < 0.001), 29.50° ± 2.46° for addressing the FR (p < 0.001), 19.86° ± 1.98° for addressing the FO (p < 0.001), and 17.44° ± 2.21° for addressing the lateral aspect of the TI (p < 0.001), while hiding the skin scar, avoiding temporalis muscle dissection, preserving flap vascularization, and decreasing the rate of bone infection and degree of orbital content retraction. CONCLUSIONS: The extended open-door technique may be specifically suited for selected patients affected by paramedian anterior and middle fossae lesions, with prevalent anteromedial extension toward the anterior clinoid, the foremost compartment of the cavernous sinus and FR and not completely controlled with the pure endoscopic transorbital approach.

The feasibility of three port endonasal, transorbital, and sublabial approach to the petroclival region: neurosurgical audit and multiportal anatomic quantitative investigation.

PURPOSE: The petroclival region represents the "Achille's heel" for the neurosurgeons. Many ventral endoscopic routes to this region, mainly performed as isolated, have been described. The aim of the present study is to verify the feasibility of a modular, combined, multiportal approach to the petroclival region to overcome the limits of a single approach, in terms of exposure and working areas, brain retraction and manipulation of neurovascular structures. METHODS: Four cadaver heads (8 sides) underwent endoscopic endonasal transclival, transorbital superior eyelid and contralateral sublabial transmaxillary-Caldwell-Luc approaches, to the petroclival region. CT scans were obtained before and after each approach to rigorously separate the contribution of each osteotomy and subsequentially to build a comprehensive 3D model of the progressively enlarged working area after each step. RESULTS: The addition of the contralateral transmaxillary and transorbital corridors to the extended endoscopic endonasal transclival in a combined multiportal approach provides complementary paramedian trajectories to overcome the natural barrier represented by the parasellar and paraclival segments of the internal carotid artery, resulting in significantly greater area of exposure than a pure endonasal midline route (8,77 cm2 and 11,14 cm2 vs 4,68 cm2 and 5,83cm2, extradural and intradural, respectively). CONCLUSION: The use of different endoscopic "head-on" trajectories can be combined in a wider multiportal extended approach to improve the ventral route to the most inaccessible petroclival regions. Finally, by combining these approaches and reiterating the importance of multiportal strategy, we quantitatively demonstrate the possibility to reach "far away" paramedian petroclival targets while preserving the neurovascular structures.

Functional and clinical outcomes after superior eyelid transorbital endoscopic approach for spheno-orbital meningiomas: illustrative case and literature review.

The pattern of growth of spheno-orbital meningiomas accounts for the main presenting symptoms, such as proptosis, eye motility deficit, visual impairment, diplopia. As these are benign tumors, the postoperative patient's quality of life is an important factor to consider during the preoperative planning. A detailed literature review of superior eyelid transorbital endoscopic approach for spheno-orbital meningiomas, including our own case, was made. A Medline search up to March 2022 in PubMed online electronic database was made using the following key phrases: "superior eyelid endoscopic transorbital approach spheno-orbital meningiomas," "superior eyelid endoscopic transorbital approach," "spheno-orbital meningiomas endoscopic approach." The inclusion criteria were surgical series, reviews, and case reports in English language, as well as papers written in other languages, but including the abstract in English. Cadaveric studies, multiportal combined approaches for SOM, were excluded. The literature review has disclosed five studies for a total of 65 patients, whose demographic, clinical, pathological, surgical, complications, and outcome data were analyzed. Functional and esthetic outcome data after superior eyelid transorbital approach are the following: improvement of proptosis (100%), of visual deficits (66.66%) and of ocular paresis (75%), with only 11 complications (4 trigeminal dysesthesia, 2 CSF leak, 2 wound complications, 1 upper eyelid necrosis, 1 hemorrhage of surgical field, 1 keratitis) reported, but at the expense of extent of resection (gross total resection 33.39%). Based on the outcome data, the superior eyelid transorbital endoscopic approach results in a suitable operative technique for selected spheno-orbital meningiomas.

Flexible endoscopic assistance in the surgical management of vestibular schwannomas.

Endoscopic-assisted techniques have extensively been applied to vestibular schwannoma (VS) surgery allowing to increase the extent of resection, minimize complications, and preserve facial nerve and auditory functions. In this paper, we retrospectively analyze the effectiveness of flexible endoscope in the endoscopic-assisted retrosigmoid approach for the surgical management of VS of various sizes. The authors conducted a retrospective analysis on 32 patients who underwent combined microscopic and flexible endoscopic resection of VS of various sizes over a period of 16 months. Flexible endoscopic-assisted retrosigmoid approach was performed in all cases, and in 6 cases, flexible and rigid endoscopic control were used in combination to evaluate the differences between the two surgical instruments. The surgical results were additionally compared with a previous case series of 141 patients operated for VS of various sizes without endoscopic assistance. Gross-total resection was achieved in 84% of the cases and near-total resection was accomplished in the rest of them. Excellent or good facial nerve function was observed in all except one case with a preoperative severe facial palsy. Hearing preservation surgery (HPS) was attempted in 11 cases and accomplished in 9 (81.8%). A tumor remnant was endoscopically identified in the fundus of the IAC in all cases (100%). Endoscopic assistance increased the rate of total removal and no intrameatal residual tumor was seen at radiological follow-up. Comparative analysis with a surgical cohort of patients operated with the sole microsurgical technique showed a significative association between endoscopic assistance and intracanalicular extent of resection. Combined microsurgical and flexible endoscopic assistance provides remarkable advantages in the pursuit of maximal safe resection of VS and preservation of facial nerve and auditory functions, minimizing the risk of post-operative complications.

Tractostorm: The what, why, and how of tractography dissection reproducibility.

Investigative studies of white matter (WM) brain structures using diffusion MRI (dMRI) tractography frequently require manual WM bundle segmentation, often called "virtual dissection." Human errors and personal decisions make these manual segmentations hard to reproduce, which have not yet been quantified by the dMRI community. It is our opinion that if the field of dMRI tractography wants to be taken seriously as a widespread clinical tool, it is imperative to harmonize WM bundle segmentations and develop protocols aimed to be used in clinical settings. The EADC-ADNI Harmonized Hippocampal Protocol achieved such standardization through a series of steps that must be reproduced for every WM bundle. This article is an observation of the problematic. A specific bundle segmentation protocol was used in order to provide a real-life example, but the contribution of this article is to discuss the need for reproducibility and standardized protocol, as for any measurement tool. This study required the participation of 11 experts and 13 nonexperts in neuroanatomy and "virtual dissection" across various laboratories and hospitals. Intra-rater agreement (Dice score) was approximately 0.77, while inter-rater was approximately 0.65. The protocol provided to participants was not necessarily optimal, but its design mimics, in essence, what will be required in future protocols. Reporting tractometry results such as average fractional anisotropy, volume or streamline count of a particular bundle without a sufficient reproducibility score could make the analysis and interpretations more difficult. Coordinated efforts by the diffusion MRI tractography community are needed to quantify and account for reproducibility of WM bundle extraction protocols in this era of open and collaborative science.

Transorbital and supraorbital uniportal multicorridor approach to the orbit, anterior, middle and posterior cranial fossa: Anatomic study.

Introduction: The transorbital route has been proposed for addressing orbital and paramedian skull base lesions. It can be complemented by further marginotomies, as per "extended-transorbital approach" and combined with others ventro-basal approaches featuring the concept of "multiportal surgery". Nevertheless, it cannot address some anatomical regions like the clinoid, carotid bifurcation and the Sylvian fissure. Therefore, we propose a combined transorbital and a supraorbital approach, attainable by a single infra-brow incision, and we called it "Uniportal multicorridor" approach. Research question: The aim of our study is to verify its feasibility and deep anatomical targets through a cadaveric study. Materials and methods: Anatomic dissections were performed at the Laboratory of ICLO Teaching and Research Center (Verona, Italy) on four formalin-fixed cadaveric heads injected with colored neoprene latex (8 sides). A stepwise dissection of the supraorbital and transorbital approaches (with an infra-brow skin incision) to the anterior tentorial incisura, clinoid area, lateral wall of the cavernous sinus, middle temporal fossa, posterior fossa, and Sylvian fissure is described. Results: We analyzed the anatomic areas reached by the transorbital corridor dividing them as follow: lateral wall of the cavernous sinus, middle temporal fossa, posterior fossa, and Sylvian fissure; while the anatomic areas addressed by the supraorbital craniotomy were the clinoid area and the anterior tentorial incisura. Conclusions: The described uniportal multi-corridor approach combines a transorbital corridor and a supraorbital craniotomy, providing a unique intra and extradural control over the anterior, middle, and posterior fossa, tentorial incisura and the Sylvian fissure, via an infra-brow skin incision.

The Course of the Trochlear Nerve Presented via a 3-Dimensional Photorealistic Anatomic Model.

OBJECTIVES: Several factors contribute to the anatomical complexity of the trochlear nerve, including small diameter, complex and longest intracranial course, deep location, and numerous neurovascular relationships. A 3-dimensional (3D) photorealistic model of the cranial nerves provides a detailed and immersive representation of the anatomy, enabling one to improve surgical planning, advanced surgical research, and training. The purpose of this work is to present a 3D photogrammetric study for a more intuitive and interactive way to explore and describe the entire course of trochlear nerve. METHODS: Two injected-fixed head human specimens (4 sides) were examined. The dissection protocol was divided into the following steps: 1) brain hemisphere exposure; 2) hemispherectomy dissecting all cranial nerves and partial removal of the free edge of the tentorium; 3) middle fossa and lateral wall of cavernous sinus exposure; and 4) orbital exposure. A detailed 3D photogrammetric model was generated for each dissection step. RESULTS: Four main volumetric models were generated during a step-by-step layered dissection of the entire nerve pathway highlighting its different segments. Finally, a full and integrated model of the entire course of the nerve was created. The models are available for visualization on monoscopic display, virtual, and augmented reality environment. CONCLUSIONS: The present photogrammetric model provides a more comprehensive understanding of the nerve's anatomy in its different segments, allows for customizable views thus simulating different perspectives, and can be a valuable alternative to traditional dissections. It is an advanced tool for surgical planning and surgical simulation as well as virtual reality representation of the anatomy.

Endoscopic Transorbital Resection of Temporal Pole Cavernoma: 2-Dimensional Operative Video.

An endoscopic transorbital approach has been recently included in the neurosurgical armamentarium.1 We present a case of a 31-year-old female patient with a history of recent-onset refractory epilepsy related to a left temporal pole cavernoma operated through a superior eyelid endoscopic transorbital approach. The operative video shows the key surgical steps to ensure optimal surgical freedom, adequate exposure, and complete tumor resection.2 The postoperative course was uneventful, and the patient obtained seizure control and good cosmetic results without postoperative complications. The brain computed tomography and MRI showed the size of bone removal and confirmed the complete removal of the lesion, respectively. At 3-month follow-up, the patient is epileptic seizures-free without medications. An endoscopic transorbital approach provides adequate exposure of the temporal pole, allowing safe tumor resection. Complication avoidance encompasses careful dissection of palpebral muscles, dynamic orbital retraction, and neuronavigation guidance; sphenoidal drilling according to key anatomic landmarks (eg, sagittal crest3); and anatomic knowledge of the cavernous sinus and internal carotid artery and its tributaries course from a transorbital perspective4 and reconstruction filling the empty spaces using fat, fascia lata, or dural substitutes. All procedures performed were approved by the ethics committee of both centers and in accordance with Declaration of Helsinki and its later amendments. The patient consented to the procedure and to the publication of her images, and appropriate consent was obtained for publication of cadaveric images.

Combined Endoscopic Endonasal Transclival and Contralateral Transmaxillary Approach to the Petrous Apex and the Petroclival Synchondrosis: Working "Around the Corner" of the Internal Carotid Artery-Quantitative Anatomical Study and Clinical Applications.

The endoscopic contralateral transmaxillary (CTM) approach has been proposed as a potential route to widen the corridor posterolateral to the internal carotid artery (ICA). In this study, we first refined the surgical technique of a combined multiportal endoscopic endonasal transclival (EETC) and CTM approach to the petrous apex (PA) and petroclival synchondrosis (PCS) in the dissection laboratory, and then validated its applications in a preliminary surgical series. The combined EETC and CTM approach was performed on three cadaver specimens based on four surgical steps: (1) the nasal, (2) the clival, (3) the maxillary and (4) the petrosal phases. The CTM provided a "head-on trajectory" to the PA and PCS and a short distance to the surgical field considerably furthering surgical maneuverability. The best operative set-up was achieved by introducing angled optics via the endonasal route and operative instruments via the transmaxillary corridor exploiting the advantages of a non-coaxial multiportal surgery. Clinical applications of the combined EETC and CTM approach were reported in three cases, a clival chordoma and two giant pituitary adenomas. The present translational study explores the safety and feasibility of a combined multiportal EETC and CTM approach to access the petroclival region though different corridors.

Transorbital Exposure of the Internal Carotid Artery: A Detailed Anatomic and Quantitative Roadmap for Safe Successful Surgery.

BACKGROUND AND OBJECTIVES: The superior eyelid endoscopic transorbital approach has rapidly gained popularity among neurosurgeons for its advantages in the treatment, in a minimally invasive fashion, of a large variety of skull base pathologies. In this study, an anatomic description of the internal carotid artery (ICA) is provided to identify risky zones related to lesions that may be approached using this technique. In this framework, a practical roadmap can help the surgeon to avoid potentially life-threatening iatrogenic vascular injuries. METHODS: Eight embalmed adult cadaveric specimens (16 sides) injected with a mixture of red latex and iodinate contrast underwent superior eyelid transorbital endoscopic approach, followed by interdural dissection of the cavernous sinus, extradural anterior clinoidectomy, and anterior petrosectomy, to expose the entire "transorbital" pathway of the ICA. Furthermore, the distance of each segment of the ICA explored by means of the superior eyelid endoscopic transorbital approach was quantitatively analyzed using a neuronavigation system. RESULTS: We exposed 4 distinct ICA segments and named the anatomic window in which they are displayed in accordance with the cavernous sinus triangles distribution of the middle cranial fossa: (1) clinoidal (Dolenc), (2) infratrochlear (Parkinson), (3) anteromedial (Mullan), and (4) petrous (Kawase). Critical anatomy and key surgical landmarks were defined to further identify the main danger zones during the different steps of the approach. CONCLUSION: A detailed knowledge of the reliable surgical landmarks of the course of the ICA as seen through an endoscopic transorbital route and its relationship with the cranial nerves are essential to perform a safe and successful surgery.

The Sellar Region as Seen from Transcranial and Endonasal Perspectives: Exploring Bony Landmarks Through New Surface Photorealistic Three-Dimensional Model Reconstruction for Neurosurgical Anatomy Training.

BACKGROUND: Virtual reality-based learning of neuroanatomy is a new feasible method to explore, visualize, and dissect interactively complex anatomic regions. We provide a new interactive photorealistic three-dimensional (3D) model of sellar region microsurgical anatomy that allows side-by-side views of exocranial and endocranial surfaces to be explored, with the aim of assisting young neurosurgery residents in learning microsurgical anatomy of this complex region. METHODS: Four head specimens underwent an endoscopic endonasal approach extended to the anterior and posterior skull base to expose the main bony anatomic landmarks of the sellar region. The same bony structures were exposed from a transcranial perspective. By using a photogrammetry method, multiple photographs from both endocranial and exocranial perspectives, different for angulations and depth, were captured, fused, and processed through dedicated software. RESULTS: All relevant bony structures were clearly distinguishable in the 3D model reconstruction, which provides several benefits in neuroanatomy learning: first, it replicates bony structures with high degrees of realism, accuracy, and fidelity; in addition, it provides realistic spatial perception of the depth of the visualized structures and their anatomic relationships; again, the 3D model is interactive and allows a 360° self-guided tour of the reconstructed object, so that the learner can read the bones and their anatomic relationship from all desired points of view. CONCLUSIONS: Detailed knowledge of key surgical landmarks representing keyholes and/or anatomic structures to not violate is mandatory for safer surgery, especially for a complex region such as the skull base. Highly accurate virtual and functional neurosurgical models, such as photogrammetry, can generate a realistic appearance to further improve surgical simulators and learn neuroanatomy.

Multimodal Use of Contact Endoscopy in Neurosurgery: Case Series with Technical Note and Literature Review.

BACKGROUND: Originally adopted for the cytological screening of cervical and uterine cancer, contact endoscopy (CE) is now widely used in several fields of oncological surgery. The CE method, with magnification power up to 150x, was designed to enhance visualization and identify microscopic changes indicative of precancerous and cancerous lesions at early stages. In this pilot study, we evaluated the multimodal applications of CE during different endoscopic intracranial neurosurgical procedures. METHODS: Twenty patients with skull base lesions underwent surgery using different minimally invasive endoscopic approaches (endonasal, transorbital, and supraorbital). CE was used to distinguish the pathology from the surrounding healthy tissue by positioning the endoscope either in proximity or directly onto the target tissue. Special attention was given to the visualization of the margins of the lesion to differentiate compression/displacement from infiltration of the normal surrounding tissue. RESULTS: With its unprecedented range of magnification, CE could clearly identify the microvascular pattern and cytological architecture of a tissue not detectable by simple white light endoscopy, with no reported damage due to heat transmission or iatrogenic injuries. All the lesions diagnosed as "presumed neoplastic tissue" by CE were confirmed by histopathology. The most promising results were observed in surgeries for meningioma and pituitary adenoma, as these lesions exhibit distinctive microvascular networks. CONCLUSIONS: CE represents a new and effective technique for the in vivo identification of pathological microvascular and tissue features, allowing preservation of normal tissue during different endoscopic approaches. The use of CE could improve diagnostic accuracy and assist in intraoperative decision-making, becoming a key tool in various applications in neurosurgical field.

Surgical management of spinal schwannomas arising from the first and second cervical roots: Results of a cumulative case series.

Objective: Schwannomas of the first and second nerve roots are rare neurosurgical entities, harboring specific surgical features that make surgical resection particularly challenging and deserve specifics dissertations. This study is a retrospectively analysis of 14 patients operated in two different neurosurgical centers: the San Filippo Neri Hospital of Rome and the Federal Centre of Neurosurgery of Tjumen. Materials and Methods: In the last 6 years, 14 patients underwent neurosurgical resection of high cervical (C1-C2) schwannomas, in two different neurosurgical centers. Patients data regarding clinical presentation, radiological findings, and surgical results were retrospectively analyzed. Results: The mean age was 50 years (range 13-74), the follow-up mean duration was 30 ± 8.5 (range 24-72 months), and there was no significant differences among different tumor locations (intradural, extradural, and dumbbell). Surgical results were excellent: gross total resection was achieved in all cases and there were no intraoperative complications or postoperative mortality. All patients presented postoperative clinical improvement except one who remained stable. Karnofsky performance status, at the last follow-up, confirmed a global clinical improvement. No vertebral artery (VA) injury neither spinal instability occurred; nerve root sacrifice was reported in one case. Conclusions: Neurosurgical treatment of C1-C2 schwannomas is associated with good outcomes in terms of extent of resection and neurological function. In particular, dumbbell shape and VA involvement do not represent limitations to achieve complete tumor resection and good clinical outcome. In conclusion, microsurgery represents the treatment of choice for C1-C2 schwannomas.

The Transorbital Approach, A Game-Changer in Neurosurgery: A Guide to Safe and Reliable Surgery Based on Anatomical Principles.

During the last few years, the superior eyelid endoscopic transorbital approach has been proposed as a new minimally invasive pathway to access skull base lesions, mostly in ophthalmologic, otolaryngologic, and maxillofacial surgeries. However, most neurosurgeons performing minimally invasive endoscopic neurosurgery do not usually employ the orbit as a surgical corridor. The authors undertook this technical and anatomical study to contribute a neurosurgical perspective, exploring the different possibilities of this novel route. Ten dissections were performed on ten formalin-fixed specimens to further refine the transorbital technique. As part of the study, the authors also report an illustrative transorbital surgery case to further detail key surgical landmarks. Herein, we would like to discuss equipment, key anatomical landmarks, and surgical skills and stress the steps and details to ensure a safe and successful procedure. We believe it could be critical to promote and encourage the neurosurgical community to overcome difficulties and ensure a successful surgery by following these key recommendations.

Inflammatory Pseudotumor Simulating a Jugular Foramen Meningioma: Case Report, Technical Video, and Literature Review.

Inflammatory pseudotumor (IP) is a nonneoplastic, reactive inflammatory process, of unknown etiology, characterized by a proliferation of connective tissue with an inflammatory infiltrate, most commonly involving the lungs and orbits. Primary intracranial IP is an extremely rare entity often arising from the meningeal structures of the skull base. We reported an extremely rare case of a primary intracranial IP located in the cerebellopontine angle, mimicking a jugular foramen meningioma. We further illustrated our microsurgical technique through a surgical video and performed a review of the pertinent scientific literature. The patient underwent gross total microsurgical resection of the tumor mass through a left retrosigmoid approach. Intraoperative neuromonitoring of the VII-VIII cranial nerve complex and lower cranial nerve was performed, and thulium laser fibers were used as a tool for tumor debulking. Postoperatively, the patient's neurologic symptoms recovered. Histopathologic studies showed dense infiltrate of T- and B-cell lymphocytes and epithelioid granulomas, compatible with the diagnosis of IP. Postoperatively, magnetic resonance imaging scans showed complete tumor resection. The patient underwent a 3-month oral corticosteroid therapy showing no signs of recurrence at the radiologic follow-up. Primary intracranial IPs are rare pathologic entities that can mimic extraaxial tumors and should be taken into consideration as a potential differential diagnosis. Complete microsurgical resection in combination with other treatments (steroids therapy, radiotherapy) is the most common treatment of choice and is associated with good outcomes and low rates of recurrence.

Indocyanine Green Endoscopy for Pituitary Adenomas with Parasellar Extension: Results from a Preliminary Case Series.

BACKGROUND: Advances in visualization tools have brought new confidence, including endoscope-integrated indocyanine (E-ICG), which makes pituitary and skull-base surgery safer and more effective. We report here our preliminary experience with the use of E-ICG to 1) visualize the cavernous segment of the internal carotid artery (ICA); and 2) functionally and anatomically preserve the pituitary gland. METHODS: A dedicated ICG-integrated endoscope was used in 15 patients with parasellar pituitary adenomas. Indocyanine was administered at 2 different time points during surgery: an early bolus of 12.5 mg at the sphenoid sinus opening to expose the position of the parasellar segment of the ICAs and to identify the position of the normal pituitary gland so that it could be preserved during tumor removal. Subsequently, a second late bolus of 12 mg of ICG was injected to obtain a real-time "wire angiographic" visualization of the flow of the ICAs. RESULTS: Gross total resection was achieved in 12 cases (80%), whereas subtotal resection was performed in the other 3 cases (20%). The pituitary gland was clearly discernable in 11 cases (91.6%). None of the patients manifested new endocrinologic deficits or major vascular complications. CONCLUSIONS: E-ICG is a safe and essential aid for pituitary adenomas invading the cavernous sinus. Its performance as a pituitary marker and real-time video angiography showed promising results in terms of extent of resection, endocrinologic outcomes, and prevention of intraoperative complications.

"Sagittal Crest": Definition, Stepwise Dissection, and Clinical Implications From a Transorbital Perspective.

BACKGROUND: The recent development of the superior eyelid endoscopic transorbital approach (SETOA) offered a new route for the management of cavernous sinus and middle cranial fossa tumors. As a result, a constant anatomic landmark of the surgical pathway after drilling the medial edge of the greater sphenoid wing (GSW) is represented by a triangular-shaped bone ridge appearing as a "crest." OBJECTIVE: To perform an anatomic study to define this surgical landmark, named the "sagittal crest" (SC) as seen from the transorbital endoscopic view. METHODS: Four adult cadaveric specimens (8 sides) were dissected performing an endoscopic transorbital approach to the middle fossa and the SC was removed to perform interdural opening of the cavernous sinus. Computed tomography scans were made before and after removal of the SC to perform quantitative analysis and building a 3-dimensional model of the bone resection of the GSW via the SETOA. RESULTS: The SC is a bone ridge triangle shaping dorsally the superior orbital fissure resulting as the residual fragment after drilling the lateral aspect of the greater sphenoid wing. Predissection and postdissection computed tomography scans allowed to objectively assess SC features and dimensions (mean 1.08 ± 0.2 cm). CONCLUSION: The SC is a constant anatomic landmark constituted of the residual medial portion of the GSW. Complete resection of this key landmark provides adequate working space and appears to be mandatory during SETOA to guide the subsequent interdural dissection of the lateral wall of cavernous sinus.

Endoscopic transorbital avenue to the skull base: Four-step conceptual analysis of the anatomic journey.

Background: In the last decades, skull base surgery had passed through an impressive evolution. The role of neuroanatomic research has been uppermost, and it has played a central role in the development of novel techniques directed to the skull base. Indeed, the deep and comprehensive study of skull base anatomy has been one of the keys of success of the endoscopic endonasal approach to the skull base. In the same way, dedicated efforts expended in the anatomic lab has been a powerful force for the growth of the endoscopic transorbital approach to the lateral skull base.Therefore, in this conceptual paper, the main steps for the anatomic description of the endoscopic transorbital approach to the skull base have been detailed. Methods: The anatomic journey for the development of the endoscopic transorbital approach to the skull base has been analyzed, and four "conceptual" steps have been highlighted. Results: As neurosurgeons, the eyeball has always represented a respectful area: to become familiar with this complex and delicate anatomy, we started by examining the orbital anatomy on a dry skull (step 1). Hence, step 1 is represented by a detailed bone study; step 2 is centered on cadaveric dissection; step 3 consists in 3D quantitative assessment of the novel endoscopic transorbital corridor; and finally, step 4 is the translation of the preclinical data in the real surgical scenario by means of dedicated surgical planning. Conclusions: The conceptual analysis of the anatomic journey for the description of the endoscopic transorbital approach to the skull base resulted in four main methodological steps that should not be thought strictly consequential but rather interconnected. Indeed, such steps should evolve following the drives that can arise in each specific situation. In conclusion, the four-step anatomic rehearsal can be relevant for the description, diffusion, and development of a novel technique in order to facilitate the application of the endoscopic transorbital approach to the skull base in a real surgical scenario.

"Limited" Extreme Lateral Infrajugular Transcondylar-Transtubercular Exposure (ELITE) for the Microsurgical Management of C1-C2 Schwannoma: Operative Video.

The extreme lateral infrajugular transcondylar-transtubercular exposure (ELITE) is a surgical approach developed in the late 1980s by Prof. T. Fukushima and represents the dorsolateral inferior skull base procedure of choice to approach lesion located ventrolaterally at the level of the craniocervical junction (CCJ). This approach consist in a suboccipital craniotomy/craniectomy with partial condylectomy and jugular tubercule drilling that can be extended providing for subtotal condylectomy and vertebral artery transposition. The "limited" variation of the ELITE approach consist in a lateral suboccipital craniectomy opening the foramen magnum and removal of at least half of the posterior arch of the atlas without condyle drilling. This surgical technique was recently demonstrated to be particularly suitable for the surgical management of spinal tumor located ventrolaterally in the upper cervical spine. This operative video illustrates step-by-step the surgical technique adopted for the microsurgical resection of a C1-C2 intradural schwannoma located antero-laterally (Video 1). ELITE approach offers a wide and adequate exposure and access to the CCJ, allowing direct visualization and access to the tumor with minimal neural manipulations, early detection of the vertebral artery and, for tumor located at C1-C2 level, without drilling the occipital condyle. In our experience, ELITE procedure is the preferred surgical approach for resection of tumors located ventrally or ventrolaterally to the first 2 cervical levels.

Minimally Invasive Microsurgical Removal of Giant Dumbbell Thoracic Neurofibroma: Usefulness of Current Technology for Minimizing the Approach-Illustrative Case and Technical Video.

Dumbbell-shaped thoracic tumors usually arise from neurogenic elements within the spinal canal and are characterized by involvement of both spinal canal and posterior thoracic cavity. The tumor mass becomes frequently very large growing inside and outside of the spinal canal, through the connection of the neural foramen, involving the surrounding structures. Most of the dumbbell tumors are peripheral nerve sheath tumors, of which neurofibromas and schwannomas represent the vast majority. Gross total resection is considered the treatment of choice and can be achieved through several combined thoracic-neurosurgical approaches. However, these operations have significant approach-related morbidity; therefore, in the last decades, thanks to the constant progress of technological devices, minimally invasive techniques have been increasingly used for the surgical management of spinal tumors. In this surgical video (Video 1), we present a minimally invasive, single-step posterolateral approach through a small costotransversectomy (centered with echography and fitted with spine navigation) for the surgical management of a giant dumbbell thoracic neurofibroma. The usefulness of current technology guiding the surgical procedure is underlined with special emphasis.