Microsurgical Resection of Trigeminal Schwannoma Through Transorbital Approach: 2-Dimensional Operative Video

We present the case of an asymptomatic 34-year-old woman who was found to have an incidental left trigeminal schwannoma.1,2 Owing to the rapid increase in size on imaging, an atypical finding for this type of lesion,3 as well as the risk of cranial nerve involvement and need for tissue diagnosis, the patient underwent a microsurgical left transorbital approach with lateral orbitotomy to resect the lesion.4,5 Piecemeal resection was performed, and the internal contents of the cavernous sinus were preserved. Ultimately, gross total resection was achieved with no residual disease identified on postoperative imaging. No new neurologic deficits were noted after surgery. The technical considerations for the transorbital approach and the literature review on the outcomes for middle fossa lesions accessed by a lateral orbitotomy are reviewed.6-10 The patient consented to the procedure and to the publication of her images. Institutional Review Board approval was deemed unnecessary due to the retrospective, case-report nature of this work.

Transorbital approach to the cavernous sinus: an anatomical study of the related cranial nerves

Background

The cavernous sinus (CS) is a demanding surgical territory, given its deep location and the involvement of multiple neurovascular structures. Subjected to recurrent discussion on the optimal surgical access, the endoscopic transorbital approach has been recently proposed as a feasible route for selected lesions in the lateral CS. Still, for this technique to safely evolve and consolidate, a comprehensive anatomical description of involved cranial nerves, dural ligaments, and arterial relations is needed.

Objective

Detailed anatomical description of the CS, the course of III, IV, VI, and V cranial nerves, and C3-C7 segments of the carotid artery, all described from the ventrolateral endoscopic transorbital perspective.

Methods

Five embalmed human cadaveric heads (10 sides) were dissected. An endoscopic transorbital approach with lateral orbital rim removal, anterior clinoidectomy, and petrosectomy was performed. The course of the upper cranial nerves was followed from their apparent origin in the brainstem, through the middle fossa or cavernous sinus, and up to their entrance to the orbit. Neuronavigation was used to follow the course of the nerves and to measure their length of surgical exposure.

Results

The transorbital approach allowed us to visualize the lateral wall of the CS, with cranial nerves III, IV, V1-3, and VI. Anterior clinoidectomy and opening of the frontal dura and the oculomotor triangle revealed the complete course of the III nerve, an average of 37 (±2) mm in length. Opening the trigeminal pore and cutting the tentorium permitted to follow the IV nerve from its course around the cerebral peduncle up to the orbit, an average of 54 (±4) mm. Opening the infratrochlear triangle revealed the VI nerve intracavernously and under Gruber's ligament, and the extended petrosectomy allowed us to see its cisternal portion (27 ± 6 mm). The trigeminal root was completely visible and so were its three branches (46 ± 2, 34 ± 3, and 31 ± 1 mm, respectively).

Conclusion

Comprehensive anatomic knowledge and extensive surgical expertise are required when addressing the CS. The transorbital corridor exposes most of the cisternal and the complete cavernous course of involved cranial nerves. This anatomical article helps understanding relations of neural, vascular, and dural structures involved in the CS approach, essential to culminating the learning process of transorbital surgery.

Exposure of the Cavernous Sinus via the Endoscopic Transorbital and Endoscopic Endonasal Approaches: A Comparative Study

OBJECTIVE

To compare the endoscopic transorbital approach (ETOA) and endoscopic endonasal approach (EEA) in terms of cavernous sinus (CS) exposure.

METHODS

Four cadaveric heads (8 sides) were dissected. The CS was accessed using the EEA and ETOA. Stereotactic measurements of the length of the main structures exposed, angles of attack, depths of surgical corridor, and areas of exposure were obtained and compared between the approaches. An illustrative case is also presented.

RESULTS

The endoscopic transorbital approach (ETOA) exposed the lateral and superior compartments of the CS without obstruction by the internal carotid artery (ICA). The EEA exposed all compartments after mobilizing the ICA. Both approaches enabled similar exposure of the cranial nerves. The depth of surgical corridor was significantly shorter with the ETOA (P < 0.01). The areas of lateral compartment exposure were similar. As the number of instruments placed into the surgical channel increased, the available angles of attack with the ETOA became smaller and were smaller than those of the EEA. In the clinical case presented, the tumor was successfully removed without complications.

CONCLUSIONS

The ETOA has the advantages of a sterile surgical channel, short operation time, little patient trauma, short surgical corridor, large exposure area, and interdural pathway; moreover, it allows dissection through the interdural space without entering the neurovascular compartment of the CS. Although the space for manipulation of instruments is limited, the ETOA is suitable for treating selected tumors in the superior and lateral compartments of the CS.

Cadaveric analysis of transcranial versus endoscopic transorbital petrosectomy: comparison of surgical maneuverability and brainstem exposure

Introduction

While accessing the posterior fossa, the anterior transpetrosal approach (ATPA) and endoscopic transorbital approach (ETOA) use the same bony landmarks during petrous apex drilling. However, owing to their contrasting surgical axes, they are expected to show differences in surgical view, maneuverability, and clinical implications. This study aimed to investigate the feasibility of ETOA in accessing the brainstem and to compare the surgical view and maneuverability of each approach.

Methods

ATPA and ETOA were performed in four human cadaveric heads (eight sides and four sides in each procedure). The angle of attack (AOA) and surgical depth were measured at the target of interest (root exit zone [REZ] of cranial nerve [CN] V, VI, and VII). When measuring the area of exposure, the brainstem was divided into two areas (anterior and lateral brainstem) based on the longitudinal line crossing the entry zone of the trigeminal root, and the area of each was measured.

Results

ATPA showed significantly greater value at the trigeminal REZ in both vertical (31.8 ± 6.7° vs. 14.3 ± 5.3°, p=0.006) and horizontal AOA (48.5 ± 2.9° vs. 15.0 ± 5.2°, p<0.001) than ETOA. The AOA at facial REZ was also greater in ATPA than ETOA (vertical, 27.5 ± 3.9° vs. 8.3 ± 3.3°, p<0.001; horizontal, 33.8 ± 2.2° vs. 11.8 ± 2.9°, p<0.001). ATPA presented significantly shorter surgical depth (CN V, 5.8 ± 0.5 cm vs. 9.0 ± 0.8, p<0.001; CN VII, 6.3 ± 0.5 cm vs. 9.5 ± 1.0, p=0.001) than ETOA. The mean area of brainstem exposure did not differ between the two approaches. However, ATPA showed significantly better exposure of anterior brainstem than ETOA (240.7 ± 9.6 mm² vs. 171.7 ± 15.0 mm², p<0.001), while ETOA demonstrated better lateral brainstem exposure (174.2 ± 29.1 mm² vs. 231.1 ± 13.6 mm², p=0.022).

Conclusions

ETOA could be a valid surgical option, in selected cases, that provides a direct ventral route to the brainstem. Compared with ATPA, ETOA showed less surgical maneuverability, AOA and longer surgical depth; however, it presented comparable brainstem exposure and better exposure of the lateral brainstem.

TransOrbital NeuroEndoscopic Surgery for Biopsy of the Left Cavernous Sinus: A Literature Review, Case Report, and Cadaveric Proof of Concept

The aim of this report is to describe TransOrbital NeuroEndoscopic Surgery (TONES) as a safe alternative for obtaining a cavernous sinus (CS) biopsy. We describe this technique in a patient with a diffuse large B cell lymphoma mimicking Tolosa-Hunt's syndrome. Articles were gathered querying PubMed, Embase, and Scopus databases with terms related to a "transorbital neuroendoscopic approach." The literature search was performed by two independent authors (N.L.F. and J.R.), with inconsistencies resolved by the senior author (M.M.D.V.). After screening abstracts for relevance, full-length articles were reviewed for pertinent variables. A comparison was conducted with the illustrative case of a 69-year-old woman who presented to the emergency department with vertigo, ophthalmoplegia, and diplopia for 2 months. A brain magnetic resonance imaging revealed an infiltrative lesion at the left CS. A presumptive diagnosis of Tolosa-Hunt syndrome was made, but a confirmatory biopsy was performed using TONES. Based on our cadaveric study, literature review, and case report, the TONES approach was safe, effective for tissue diagnosis, and associated with minor morbidity and reduced hospital stay. Additional prospective studies are required to study its viability and safety in a larger group of patients.

Indications and outcomes of endoscopic transorbital surgery for trigeminal schwannoma based on tumor classification: a multicenter study with 50 cases

OBJECTIVE

Trigeminal schwannoma is a rare CNS tumor and involves the multicompartmental skull base. Recently, the endoscopic transorbital approach (ETOA) has emerged as a technique for minimally invasive surgery. The objective of this study was to evaluate the optimal indications and clinical outcomes of the ETOA for trigeminal schwannomas based on their tumor classification.

METHODS

Between September 2016 and February 2022, the ETOA was performed in 50 patients with trigeminal schwannoma at four tertiary hospitals. There were 15 men and 35 women in the study, with a mean age of 46.9 years. All tumors were classified as type A (predominantly involving the middle cranial fossa), type B (predominantly involving the posterior cranial fossa), type C (dumbbell-shaped tumors involving the middle and posterior fossa), or type D (involvement of the extracranial compartment). Type D tumors were also subclassified by ophthalmic division (D1), maxillary division (D2), and mandibular division (D3). Clinical outcome was analyzed, including extent of resection and surgical morbidities.

RESULTS

In this study, overall gross-total resection (GTR) was performed in 35 (70.0%) of 50 patients and near-total resection (NTR) in 9 patients (18.0%). The mean follow-up period was 21.9 (range 1-61.7) months. There was no tumor regrowth or recurrence during the follow-up period. Based on the classification, there were 17 type A tumors, 20 type C, and 13 type D. There were no type B tumors. Of the 13 type D tumors, 7 were D1, 1 D2, and 5 D3. For type A tumors, GTR or NTR was achieved using an ETOA in 16 (94.1%) of 17 patients. Eighteen (90.0%) of 20 patients with type C tumors attained GTR or NTR. Ten (76.9%) of 13 patients with type D tumors underwent GTR. Statistical analysis showed that there was no significant difference in the extent of resection among the tumor subtypes. Surgical complications included transient partial ptosis (n = 4), permanent ptosis (n = 1), transient diplopia (n = 7), permanent diplopia (n = 1), corneal keratopathy (n = 7), difficulties in mastication (n = 5), and neuralgic pain or paresthesia (n = 14). There were no postoperative CSF leaks or enophthalmos during follow-up.

CONCLUSIONS

This study showed that trigeminal schwannomas can be effectively treated with a minimally invasive ETOA in all tumor types, except those predominantly involving the posterior fossa (type B). For the extracranial compartments, D2 or D3 tumor types often require an ETOA combined with the endoscopic endonasal approach, while D1 tumor types can be treated using an ETOA alone.

Endoscopic transorbital approach for skull base lesions: a report of 16 clinical cases

Due to the deep location, complex anatomy, and adjacent vital neurovascular structures, skull base surgery is challenging and requires specific approaches. The emerging endoscopic transorbital approach (eTOA) technique provides a new approach to the orbital content, spheno-orbital region, lateral cavernous sinus, and Meckel's cave. In this study, the clinical utility and effectiveness of the eTOA are reported. Sixteen cases who underwent the eTOA were included in the current study. The patients were divided into 3 groups according to tumor location: Group A (intraorbital, 6 cases), group B (spheno-orbital, 7 cases), and group C (cavernous sinus, and Meckel's cave, 3 cases). The clinical data and surgical results were analyzed. Eight meningiomas, 2 hemangiomas, 1 low-grade glioma, 1 instance of inflammatory hyperplasia tissue, 1 Langerhans cell histiocytosis, 1 epidermoid cyst, 1 trigeminal schwannoma, and 1 bone fibrosis hyperplasia were observed. The mean tumor diameter was 2.4 cm. A single case in Group A and Group C underwent biopsy (12.5%), and 1 case of fibrous dysplasia in Group B underwent sufficient orbit decompression (6.25%). The remaining 13 cases underwent gross total tumor resection (81.25%). No cerebral-spinal fluid leak or infection occurred. And no cosmetic problems or significant complications were observed during the follow-up. As a minimally invasive technique, the eTOA has unique advantages for carefully selected skull base lesions because of its direct route, short working distance, and distinct attack angle.

A Novel Sublabial Anterior Transmaxillary Approach for Medically Refractory Mesial Temporal Lobe Epilepsy: A Comparative Anatomic Study

BACKGROUND

Current approaches for mesial temporal lobe epilepsy may result in suboptimal seizure control and cognitive decline. An incomplete treatment of the epileptogenic zone and unnecessary violation of functional cortical and subcortical areas may contribute to suboptimal results.

OBJECTIVE

To describe and test the anatomic feasibility of a novel endoscopic anterior transmaxillary (ATM) approach to the temporal lobe and to compare the described technique to other transfacial approaches.

METHODS

Twenty-four cadaveric brain hemispheres fixed in formalin were used to study anterior temporal surface anatomy. Two additional hemispheres were fixed in formalin and then frozen for white matter dissections. Subsequently, bilateral dissections on 4 injected cadaveric heads were used to describe the endoscopic ATM approach and to evaluate various anterior endoscopic corridors for the temporal pole and mesial temporal lobe structures.

RESULTS

The ATM approach was considered superior because of direct visualization of the temporal pole and natural alignment with the mesial temporal structures. The mean exposure corridor covered 49.1° in the sagittal plane and 66.2° in the axial plane. The ATM allowed direct access lateral to the maxillary and mandibular nerves with an anterior-posterior trajectory aligned to the longitudinal axis of the hippocampus formation, allowing for a selective amygdalohippocampectomy with preservation of the trigeminal branches and the lateral temporal neocortex.

CONCLUSION

The ATM approach is anatomically feasible, providing a direct and selective approach for the temporal pole and mesial temporal lobe structures, with a substantial angle of visualization because of its direct alignment with the mesial temporal lobe structures.

Modified Lateral Orbitotomy Approach to Lesions of the Orbital Apex, Superior Orbital Fissure, Cavernous Sinus, and Middle Cranial Fossa

BACKGROUND

The lateral orbitotomy approach (LOA) provides minimally invasive access to the orbit, cavernous sinus region, and middle cranial fossa. Orbital retraction with this approach can nonetheless injure orbital structures, causing unnecessary morbidity.

OBJECTIVE

To describe our clinical experience with the modified LOA (mLOA), wherein the medial aspect of the lateral orbital wall posterior to the orbital rim is preserved.

METHODS

This is a retrospective, single-institution case series of patients undergoing a mLOA for lesions of the orbital apex, superior orbital fissure, cavernous sinus, and middle cranial fossa. The dimensions and variance of selected anatomic parameters relevant to this approach (orbital rim-superior orbital fossa depth, lateral orbital wall angle) were also analyzed using computed tomography scans from 30 adult patients.

RESULTS

Eight patients underwent a mLOA (mean age 54.0 ± 19.6 years; 3 males). Surgical targets included the superior orbital fissure (2; cavernoma and meningioma), sphenoid wing with or without the orbital apex (2; meningioma), cavernous sinus (2; rule out carcinoma and smooth muscle tumor), and anterior/mesial temporal lobe (2; cavernoma). Visual acuity/fields and diplopia was stable or improved in all patients postoperatively. One patient experienced a cerebrospinal fluid leak. On computed tomography analysis, the relevant bony anatomy displayed limited variability, with a mean orbital fossa depth of 42.7 ± 2.8 mm and a lateral orbital wall angle of 44.4° ± 2.7°.

CONCLUSION

The mLOA can provide safe, minimally invasive access to select lesions of the orbital apex, superior orbital fissure, cavernous sinus, and middle cranial fossa. The operative corridor has relatively consistent bony anatomy.

Lateral transorbital approach: an alternative microsurgical route for supratentorial cerebral aneurysms

OBJECTIVE

Transorbital approaches for neurosurgery have recently attracted attention and several anatomical studies have aimed to improve these techniques, but significant deficiencies in clinical practice remain, especially for aneurysm surgery. The authors present an alternative microsurgical route and the results of an analysis of patients with intracranial aneurysms who underwent a lateral transorbital approach (LTOA) using lateral orbito-zygoma-sphenotomy (LOZYGS).

METHODS

The clinical and surgical results of a series of 54 consecutive patients with 1 or more aneurysms who underwent surgery via LTOA are reported. A lateral orbitotomy was performed after making a 3-cm skin incision parallel to the lateral orbital rim. A second bone flap, which included the zygoma and sphenoid bones that form the lateral orbital wall, was removed. The lesser sphenoid wing, including the anterior clinoid process, was fully drilled, except in cases of middle cerebral artery (MCA) aneurysms. Cisternal dissection was performed using the classic microsurgical technique starting from the proximal Sylvian fissure and carotid cistern. After the aneurysm was clipped following microsurgical principles, the dura mater was closed in a watertight fashion and 2-piece bone reconstruction was achieved.

RESULTS

Sixty aneurysms in 54 patients were clipped using the LOZYGS route. Twenty-one aneurysms were located on the MCA, 30 on the anterior communicating artery, 8 on the internal carotid artery, and 1 at the apex of the basilar artery. The unruptured-to-ruptured aneurysm ratio was 17:43. The operative field was moved to the orbit using the LTOA to avoid interference by bone and muscle tissues. Early proximal control was achieved using a short working distance and direct exposure of the base of the cerebrum, without any requirement for retraction. Because different view angles and surgical corridors were used, no segment of the aneurysm or the parent artery remained unexposed. Therefore, the introduction of additional tools was not required.

CONCLUSIONS

The LTOA allowed enhanced broad-perspective exposure of the operative field, early proximal control, and satisfactory surgical freedom. This alternative surgical approach safely exposed the target area and the operative field. The LOZYGS route is safe and effective for the LTOA and microsurgical clipping of anterior circulation aneurysms. According to the authors' surgical experience and clinical experience, the LTOA can be considered an alternative surgical route to supratentorial aneurysm surgery.

Surgical Approaches to the Orbit: A Neurosurgical Perspective

Orbital pathologies can be complex to manage surgically. In this article, we describe some of the most common and relevant approaches to orbital tumours. For each approach we describe the appropriate indications, surgical technique, potential complications, and illustrate a case example.

The transsylvian corridor through minimally invasive transcranial approaches: a comparative anatomical study

Minimally invasive transcranial approaches (MITAs) continue to expand in popularity in neurosurgery. Only few MITAs allow sufficient sylvian exposure to enable wide use of the transsylvian corridor. In this study, we aim to compare the transsylvian corridor in two MITAs: the minipterional (MPTa) and the extended supraorbital eyebrow approaches (XSEa). Eight cadaver heads were used to quantify the surgical exposure and maneuverability along the sylvian fissure and the insular lobe provided by the MPTa and the XSEa. Surgical exposure was calculated by means of the exposed length of the sylvian fissure and by the area framed within three extreme points in the insular lobe. Maneuverability was assessed by means of the surgical freedom along the sylvian cistern. XSEa provides twice the frontal exposure and half of the temporal exposure in comparison to the MPTa (p < 0.001 and p = 0.02, respectively). No significant differences were found between the two craniotomies in the length of the exposure of the sylvian fissure, area of insular exposure, or surgical freedom. Both the MPTa and the XSEa afford sufficient grades of exposure along the sylvian fissure and the insular lobe, although the viewing angle is significantly different between the two approaches. Such properties allow either to be used for microsurgery deep within the sylvian cistern. The use of additional corridors, such as the subfrontal route (XSEa) and pretemporal route (MPTa), may influence selection of either the minipterional or the extended supraorbital approaches according to the origin of the surgical pathology addressed.

Lateral Transorbital Versus Endonasal Transpterygoid Approach to the Lateral Recess of the Sphenoid Sinus-A Comparative Anatomic Study

BACKGROUND

The treatment of cerebrospinal fluid leaks of the lateral recess of the sphenoid sinus (LRSS) faces difficulties due to the deep location of the osseous defect. When treated with craniotomies, brain retraction is a concern. The endoscopic endonasal transpterygoid approach (EETA) is a direct and less invasive procedure; however, it may require transection of the vidian nerve (VN).

OBJECTIVE

To investigate the feasibility of a lateral transorbital approach (LTOA) as an alternative pathway to the LRSS that avoids VN sacrifice.

METHODS

Six embalmed heads with well-pneumatized LRSS were preselected by inspecting their computed tomography scans. One LTOA and one EETA were performed on 1 side of each specimen. The approaches were compared regarding working distance and neurovascular structures being sacrificed. The working area of the LTOA was also measured.

RESULTS

The average working distances were 59.9 (±2.94) mm for the LTOA and 76.4 (±3.99) mm for the EETA (P < .001). The LTOA generated a working area with a diameter of 9 to 14 mm. The EETA demanded the sacrifice of VN and the sphenopalatine artery in all specimens to expose the LRSS. No neurovascular structures were found in the trajectory of the LTOA.

CONCLUSION

The LTOA to the LRSS is feasible, with minimal risk of injuring neurovascular structures. It offers a shorter pathway when compared to the EETA. Although the LTOA provides no options for vascularized flap reconstruction, it allows immediate access to muscle grafts. The LTOA may serve as an alternative to treating cerebrospinal fluid leaks of the LRSS.

Minimally Invasive Lateral Paraorbital Approach for Repairing Lateral Recess of the Sphenoid Sinus Spinal Fluid Leak

BACKGROUND

Cerebrospinal fluid (CSF) leaks in the lateral recess of the sphenoid sinus (LRSS) are typically spontaneous in nature and require surgical repair. Endoscopic endonasal approaches have become the mainstay of CSF leak repair in the LRSS, though they remain technically challenging and place the vidian nerve (VN) and sphenopalatine artery (SPA) at risk. Here we present a lateral paraorbital approach (LPOA) as a minimally invasive transcranial VN and SPA sparing alternative for LRSS CSF leak repairs.

CASE DESCRIPTION

A 41-year-old African American woman presented with headaches and was found to have a spontaneous CSF leak in the LRSS. A LPOA was used to repair the CSF leak. An incision was made along the frontal process of zygoma (FPZ). Removal of the overhanging portion of the FPZ while sparing the lateral orbital rim and retraction of the temporalis muscle allowed for a tangential approach to the LRSS. A small encephalocele was seen and resected; the defect was identified and repaired with onlay DuraGen (Integra LifeSciences, Princeton, NJ) and Dura Repair (J&J Medical Devices, New Brunswick, NJ). There were no postoperative complications or recurrence of CSF leak.

CONCLUSIONS

The LPOA can be a useful alternative approach to the LRSS for CSF leak repair. The lateral-to-medial approach to defects in this area provides a shorter working distance while avoiding critical neurovascular structures.

Biportal endoscopic transorbital approach: a quantitative anatomical study and clinical application

BACKGROUND

We devised a biportal endoscopic transorbital approach (BiETOA) to gain surgical freedom by making a port for the endoscope and investigated the benefits and limitations of BiETOA.

METHODS

A cylindrical port was designed and 3-D printed using biocompatible material. The port was inserted through a keyhole between the superolateral side of the orbital rim and the temporal muscle. An endoscope was inserted through the port, and other instruments were inserted through the conventional transorbital route. BiETOA was used to dissect eight cadaveric heads, and the angle of attack and surgical freedom were assessed.

RESULTS

The mean maximal angle of attack was significantly different in BiETOA and endoscopic transorbital approach (ETOA) (P < 0.01) but not in BiETOA and ETOA lateral orbital rim (LOR) osteotomy (P = 0.207, P = 0.21). The mean surgical freedom was significantly different in BiETOA and ETOA (P < 0.01) and in BiETOA and ETOA LOR osteotomy (P < 0.01). In the clinical cases, tumors were removed successfully without any complications.

CONCLUSIONS

BiETOA provided increased surgical freedom and better visibility of deep target lesion and resulted in good surgical and cosmetic outcomes.

The Lateral Orbitotomy Approach for Intraorbital Lesions

The lateral orbitotomy approach (LOA) was first described by Kronlein in 1888 and has since been subject to many modifications and variations. When considering orbital approaches, the location of the pathology is often more important in decision making than the type of pathology. The LOA is best suited for access to intraconal and extraconal lesions lateral to the optic nerve. Pathologies treated via the LOA include primary orbital tumors, extraorbital tumors with local extension into the orbit, and distantly metastatic lesions to the orbit. These all often initially manifest with vision loss, oculomotor deficits, or proptosis. The expertise of a multidisciplinary team is needed to execute safe and effective treatment. Collaboration between many specialties may be required, including ophthalmology, neurosurgery, otolaryngology, plastic surgery, oncology, and anesthesiology. The modern technique involves either a lateral canthotomy or eyelid crease incision with removal of the lateral orbital wall. It affords many advantages over a pterional craniotomy, primarily a lower approach morbidity and superior cosmetic outcomes. Reconstruction is fairly simple and the rate of complications-vision loss and extraocular muscle palsy-are low and infrequently permanent. Deep orbital apex location and intracranial extension have traditionally been considered limitations of this approach. However, with increased surgeon comfort, modern technique, and the adoption of endoscopy, these limits have expanded to even include primarily intracranial pathologies. This review details the LOA, including the general technique, its indications and limitations, reconstruction considerations, complications, and recent data from case series. The focus is on microscopic access to intraorbital lesions.

In vivo evaluation of retinal ganglion cells and optic nerve's integrity in large animals by multi-modality analysis

Large animal models of optic nerve injury are essential for translating novel findings into effective therapies due to their similarity to humans in many respects. However, most current tests evaluating the integrity of retinal ganglion cells (RGCs) and optic nerve (ON) are based on rodent animal models. We aimed to evaluate and optimize the in vivo methods to assess RGCs and ON's function and structure in large animals in terms of reproducibility, simplicity and sensitivity. Both goats and rhesus macaques were employed in this study. By using goats, we found anesthesia with isoflurane or xylazine resulted in different effects on reproducibility of flash visual evoked potential (FVEP) and pattern electroretinogram (PERG). FVEP with the large-Ganzfeld stimulator was significantly more stable than that with mini-Ganzfeld stimulator. PERG with simultaneous binocular stimulation, with superior simplicity over separate monocular stimulation, was appliable in goats due to undetectable interocular crosstalk of PERG signals. After ON crush in goats, some FVEP components, PERG, OCT and PLR demonstrated significant changes, in line with the histological study. By using rhesus macaque, we found the implicit time of PVEP, FVEP and PERG were significantly more reproducible than amplitudes, and OCT and PLR demonstrated small intersession variation. In summary, we established an optimized system to evaluate integrity of RGCs and ON in large animals in vivo, facilitating usage of large animal models of optic nerve diseases.

ICAR: endoscopic skull-base surgery

BACKGROUND

Endoscopic skull-base surgery (ESBS) is employed in the management of diverse skull-base pathologies. Paralleling the increased utilization of ESBS, the literature in this field has expanded rapidly. However, the rarity of these diseases, the inherent challenges of surgical studies, and the continued learning curve in ESBS have resulted in significant variability in the quality of the literature. To consolidate and critically appraise the available literature, experts in skull-base surgery have produced the International Consensus Statement on Endoscopic Skull-Base Surgery (ICAR:ESBS).

METHODS

Using previously described methodology, topics spanning the breadth of ESBS were identified and assigned a literature review, evidence-based review or evidence-based review with recommendations format. Subsequently, each topic was written and then reviewed by skull-base surgeons in both neurosurgery and otolaryngology. Following this iterative review process, the ICAR:ESBS document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:ESBS document addresses the role of ESBS in primary cerebrospinal fluid (CSF) rhinorrhea, intradural tumors, benign skull-base and orbital pathology, sinonasal malignancies, and clival lesions. Additionally, specific challenges in ESBS including endoscopic reconstruction and complication management were evaluated.

CONCLUSION

A critical review of the literature in ESBS demonstrates at least the equivalency of ESBS with alternative approaches in pathologies such as CSF rhinorrhea and pituitary adenoma as well as improved reconstructive techniques in reducing CSF leaks. Evidence-based recommendations are limited in other pathologies and these significant knowledge gaps call upon the skull-base community to embrace these opportunities and collaboratively address these shortcomings.

Minimally Invasive Approaches to the Lateral Cavernous Sinus and Meckel's Cave: Comparison of Transorbital and Subtemporal Endoscopic Techniques

BACKGROUND

Transorbital and subtemporal keyhole approaches have recently been proposed to approach lesions in the lateral wall of the cavernous sinus (CS) and Meckel's cave (MC). Our goal was to compare these approaches and suggest indications for each of them.

METHODS

Five cadaver heads (10 sides, 40 procedures) were used. The lateral transorbital approaches were carried out without and with the removal of the lateral orbital rim, herein referred to as the lateral transorbital approach (LTOA) and the lateral orbital wall approach (LOWA). The subtemporal approaches were performed without and with the removal of the zygomatic arch, referred to as the subtemporal approach (STA) and the subtemporozygomatic approach (STZA). Five targets were chosen and 2 triangles were created representing the lateral wall of the CS and MC. Stereotactic measurements were quantified to calculate angles of attack, surgical freedom, and temporal lobe retraction for each approach.

RESULTS

LTOA presented the smaller horizontal angles of attack. LOWA increased the angles to the same level of STA and STZA. STA and STZA presented larger vertical angles of attack. The surgical freedom presented gradual increase from LTOA to LOWA, STA, and STZA. STA and STZA needed greater temporal lobe retraction for most targets.

CONCLUSIONS

LTOA is a good option to biopsy a lesion in the lateral wall of the CS and LOWA increased the surgical corridor to work with microsurgical techniques. STA and STZA could be better options when wide exposure is necessary, but temporal lobe retraction should be taken into consideration.

Comparative Analysis of Endoscopic Transorbital Approach and Extended Mini-Pterional Approach for Sphenoid Wing Meningiomas with Osseous Involvement: Preliminary Surgical Results

OBJECTIVE

Sphenoid wing meningiomas (SWMs) can be treated with complete surgical resection and the recently introduced endoscopic transorbital approach (ETOA) offers a minimally invasive alternative. In this study, the surgical outcome of ETOA and the extended mini-pterional approach (eMPTA) for SWMs with osseous involvement is compared.

METHODS

From October 2015 to May 2019, 24 patients underwent surgery for SWMs with osseous involvement. Among them, tumor resection was performed by ETOA for 11 patients (45.8%) and eMPTA for 13 patients (54.2%). The tumor characteristics, surgical outcome and morbidity, and approach-related aesthetic outcome were analyzed and compared retrospectively between ETOA and eMPTA based on SWM classification.

RESULTS

The location of SWMs was mostly the middle sphenoid ridge (group III) (45.8%), followed by the greater sphenoid wing (group IV) (29.2%). Simpson resection grades I/II were achieved in 9 of 11 patients (81.8%) with ETOA and 11 of 13 patients (84.6%) with eMPTA. There were no differences in tumor characteristics between the 2 approaches. Surgery time, surgical bleeding, and hospital length of stay were significantly shorter with ETOA. Three patients had transient surgical morbidities such as diplopia (n = 1), ptosis (n = 1), and cerebrospinal fluid leak (n = 1) after ETOA. No differences could be seen in surgical morbidities between ETOA and eMPTA.

CONCLUSIONS

ETOA can provide direct access to the sphenoid bone and resectability with a more rapid and minimally invasive exposure than does eMPTA. Maximal subtotal resection with extensive sphenoid bone decompression for tumors with cavernous sinus infiltration is the key to a good clinical outcome, regardless of the surgical approach.

An Anatomical Feasibility Study for Revascularization of the Ophthalmic Artery. Part II: Intraorbital Segment

INTRODUCTION

Distal ophthalmic artery (OpA) aneurysms are a rare subset of vascular lesions with lack of optimal treatment. The management of these aneurysms may require complete occlusion of the parent vessel, carrying a risk of permanent visual impairment due to individual variations of extracranial collateral flow to the intraorbital ophthalmic artery (iOpA).

OBJECTIVE

To test the feasibility of a superficial temporal artery (STA) to iOpA bypass to prevent acute ischemic retinal injury. Two different transorbital corridors (superomedial and posterolateral approaches) for this bypass were evaluated.

METHODS

Each approach was carried out in 10 specimens each (n = 20). The corridors were compared to achieve the optimal exposure of the iOpA until the central retinal artery origin was visualized. An end-to-end anastomosis was performed from STA-to-iOpA. The arterial caliber and length at the anastomotic sites, required donor artery length, and intraorbital surgical area were measured.

RESULTS

STA-iOpA bypasses were performed in all specimens. For the posterolateral transorbital approach, the mean caliber of STA was 1.8 ± 0.2 mm, and that of iOpA was 1.7 ± 0.5 mm. The required STA graft length was 78.3 ± 1 mm with lateral iOpA transposition of 8.2 ± 1.1 mm. For the superomedial approach, the average STA length required for an intraorbital bypass was 130.8 ± 14.0 mm. The mean calibers of iOpA and STA were 1.5 ± 0.1 mm and 1.5 ± 0.1 mm, respectively.

CONCLUSIONS

This study demonstrates the feasibility of a novel revascularization technique of the iOpA using 2 different transorbital approaches. These techniques can be used in the management of intraorbital lesions such as OpA aneurysms, tumoral infiltrations, or intraoperative injuries.

Quantitative analysis of the surgical exposure and surgical freedom between transcranial and transorbital endoscopic anterior petrosectomies to the posterior fossa

OBJECT

This study proposes a variation of the transorbital endoscopic approach (TOEA) that uses the lateral orbit as the primary surgical corridor, in a minimally invasive fashion, for the posterior fossa (PF) access. The versatility of this technique was quantitatively analyzed in comparison with the anterior transpetrosal approach (ATPA), which is commonly used for managing lesions in the PF.

METHODS

Anatomical dissections were carried out in 5 latex-injected human cadaveric heads (10 sides). During dissection, the PF was first accessed by TOEAs through the anterior petrosectomy, both with and without lateral orbital rim osteotomies (herein referred as the lateral transorbital approach [LTOA] and the lateral orbital wall approach [LOWA], respectively). ATPAs were performed following the orbital approaches. The stereotactic measurements of the area of exposure, surgical freedom, and angles of attack to 5 anatomical targets were obtained for statistical comparison by the neuronavigator.

RESULTS

The LTOA provided the smallest area of exposure (1.51 ± 0.5 cm2, p = 0.07), while areas of exposure were similar between LOWA and ATPA (1.99 ± 0.7 cm2 and 2.01 ± 1.0 cm2, respectively; p = 0.99). ATPA had the largest surgical freedom, whereas that of LTOA was the most restricted. Similarly, for all targets, the vertical and horizontal angles of attack achieved with ATPA were significantly broader than those achieved with LTOA. However, in LOWA, the removal of the lateral orbital rim allowed a broader range of movement in the horizontal plane, thus granting a similar horizontal angle for 3 of the 5 targets in comparison with ATPA.

CONCLUSIONS

The TOEAs using the lateral orbital corridor for PF access are feasible techniques that may provide a comparable surgical exposure to the ATPA. Furthermore, the removal of the orbital rim showed an additional benefit in an enhancement of the surgical maneuverability in the PF.

A Modified Lateral Orbitotomy Approach to the Superior Orbital Fissure: A Video Case Report and Review of Anatomy

BACKGROUND

The lateral orbitotomy approach (LOA) is often used for accessing the orbital contents and middle skull base; however, most prior descriptions of the LOA involve complete drilling of the lateral orbital wall. This practice requires retraction of the orbital contents and produces postoperative diplopia that the patient experiences for a limited time.

OBJECTIVE

To describe a modified LOA with partial sparing of the lateral orbital wall for accessing lesions of the superior orbital fissure (SOF).

METHODS

One patient with a progressively enlarging SOF lesion and visual loss underwent a modified LOA for resection. The orbital rim lateral to the SOF was removed as a bone flap, and the greater wing of the sphenoid inferior to the SOF was drilled to expose the lesion. The lateral orbital wall was thinned but was not completely removed. The orbital rim was resecured with miniplates and screws.

RESULTS

Gross total resection of the SOF mass was achieved without unnecessary exposure or retraction of the orbital contents. Histopathologic analysis of the resected mass was consistent with a cavernous hemangioma. The patient had a good cosmetic outcome without complication.

CONCLUSION

Modified LOA with partial sparing of the lateral orbital wall is a feasible approach for lesions of the SOF.

Orbital Tumors: Report of 70 Surgically Treated Cases

OBJECTIVE

The orbital cavity is an anatomically complex region and an area of interest of many specialists, each of whom is familiar with specific surgical approaches.

METHODS

We retrospectively reviewed clinical and outcome data of 70 patients who underwent surgery for resection of an orbital tumor with a mean follow-up of 111.9 ± 79.6 months. The clinical outcome was reported and the role of sex, age, histology, tumor location, tumor size, and surgical approach on the extent of tumor removal was assessed.

RESULTS

Total removal was achieved in 74.3%, subtotal removal in 20%, and partial removal in 5.7% of patients. A fronto-orbital craniotomy was used in 57.1% of cases, frontal approach in 17.1%, fronto-orbit-zygomatic approach in 10%, and endoscopic endonasal approach in 11.4%. Complications included visual acuity decrease (4.3%), cerebrospinal fluid leak (4.3%), nerve palsy (10%; supra-orbital nerve 4.3%; frontal branches of facial nerve 2.9%, third cranial nerve 2.9%), and enophthalmos (1.4%). Lateral orbitotomy, combined fronto-orbital and maxillotomy, and trans-eyelid approaches were used in the remaining cases. The fronto-orbital, frontal, and lateral orbitotomy approaches were associated with greater rates of total resection as compared with the fronto-orbit-zygomatic approach, which was used in difficult cases in which the tumor involved several regions.

CONCLUSIONS

We recommend, 1) the endoscopic endonasal approach for primary orbital tumors located in the medial or inferior orbital walls without extra-orbital extension; 2) the trans-eyelid approach for tumors of the upper and upper-lateral quadrants extraconally located, and 3) the fronto-orbital approach for intraconally located tumors involving more than one quadrant.

Comparative Analysis Between Lateral Orbital Rim Preservation and Osteotomy for Transorbital Endoscopic Approaches to the Cavernous Sinus: An Anatomic Study

BACKGROUND

Transorbital endoscopic approach (TOEA) to the cavernous sinus (CS) is a novel surgical technique. However, the necessity of lateral orbital rim (LOR) osteotomy is questionable.

OBJECTIVE

To illustrate the surgical dissection of TOEAs to CS and to investigate the additional benefit of LOR osteotomy.

METHODS

Anatomic dissections were carried out in 7 cadaveric heads (14 sides). The TOEAs were performed before and after LOR osteotomy; herein referred as the lateral transorbital approach (LTOA) and the lateral orbital wall approach (LOWA), respectively. The stereotactic measurements of the area of exposure, surgical freedom, and angles of attack around CS were quantified.

RESULTS

LOWA increased larger area of exposure than LTOA at entry site (5.3 ± 0.6 cm2 and 2.6 ± 0.6 cm2, respectively; P &lt; .001) but both of these techniques provided similar area of exposure at the surgical target site. With regard to the surgical freedoms, those afforded by LOWA were all significantly superior at all of the surgical targets with the difference ranged from 106.6% to 172.5%. No significant differences were found between the vertical angles produced by either approach. On the other hand, the horizontal angles achieved by LOWA were significantly more favorable.

CONCLUSION

The TOEAs, either with or without LOR osteotomy are feasible for CS exposure. Although the incremental effect of maneuverability is attained following the LOR osteotomy, it should be performed selectively. Additional research is needed to further validate the safety and efficacy, as well as for precisely defining the clinical application of these techniques.