Advantages and limitations of orbital rim resection in transorbital endoscopic approach: an anatomical study

BACKGROUND

Endoscopic transorbital approach (eTOA) has been recently proposed as an alternative skull base approach. However, its feasibility for deeper lesions can be hampered by a reduced surgical maneuverability. Aim of this study is to consider how its extension through orbital rim resection can overcome this limitation, and to compare two different techniques for its removal.

METHODS

Both sides of seven cadaveric fresh frozen head were dissected. Three different surgical approaches were performed consequentially (standard eTOA, its expansion with lateral orbital rim hinge removal, and with its complete resection). Distance to target and angle of attack have been measured for superior orbital fissure (SOF), lateral wall of cavernous sinus (LWCS), anterior clinoid process (ACP), foramen rotudum (FR) and foramen ovale (FO).

RESULTS

The angle of attack to the SOF (p = 0.01), to the LWCS (p = 0.001), to the ACP (p = 0.01), to the FR (p = 0.01) and to FO (p = 0.01) resulted larger in extended approaches with orbital rim resection, as well as the distance to target of LWCS (p = 0.04). Particularly, we observed that hinge lateral orbital rim removal improved the angle of attack to SOF (p = 0.02), APC (p = 0.01), FR (p = 0.01 and FO (p = 0.01) in comparison to the standard eTOA.

CONCLUSION

Our study confirms that the lateral orbital rim resection could significantly expand the surgical room and the instruments maneuverability for the considered target skull base targets. Its hinge removal could balance the clinical outcome with the increase of the angles of attack for the more medial and deeper structures.

Transorbital Microsurgery: An Anatomical Description of a Minimally Invasive Corridor to the Anterior Cranial Fossa and Paramedian Structures

Objectives  Transorbital neuroendoscopic surgery (TONES) has ignited interest in the transorbital access corridor, increasing its use for single and multi-portal skull base interventions. However, the crowding of a small corridor and two-dimensional viewing restrict this access portal. Design  Cadaveric qualitative study to assess the feasibility of transorbital microsurgery (TMS). Setting  Anatomical dissection steps and instrumentation were recorded for homogeneous methodology. Participants  Six cadaveric specimens were systematically dissected using TMS to the anterior cranial fossa and paramedian structures. Main Outcome Measures  Anatomical parameters of the TMS craniectomy were established, and the visible and accessible neuroanatomy was highlighted. Results  A superior lid crease incision achieved essential orbital rim exposure and preseptal dissection. The orbital roof craniectomy is defined by three boundaries: (1) frontozygomatic suture to the frontosphenoid suture, (2) frontal sinus and cribriform plate, and (3) frontal sinus and orbital rim. The mean (standard deviation) craniectomy was 440 mm 2 (78 mm 2 ). Exposing the ipsilateral optic nerve and internal carotid artery obviated the need for frontal lobe retraction to identify the A1-M1 bifurcation as well as near-complete visualization of the M1 artery. Conclusion  TMS is a feasible corridor for intracranial access. Mobilization of orbital contents is imperative for maximal intracranial access and protection of the globe. TMS enables access to the frontal lobe base, ipsilateral optic nerve, and most of the ipsilateral anterior circulation. This cosmetically satisfactory approach causes minimal destruction of the anterior skull base with satisfactory exposure of the anterior cranial fossa floor without sinus invasion.

Neuroanatomical perspectives on transorbital approaches: A meta-analysis

Background

Transorbital approaches represent a paradigm shift in skull base surgery, focusing on minimally invasive techniques that prioritize patient outcomes and surgical precision. The scientific community, recognizing the significance of these advances, necessitates a possible review and meta-analysis to encapsulate the collective efficacy, safety, and developmental trajectory of these approaches.

Methods

This was a literature review targeting literature in the past 10 years to present evidence for studies on surgical approaches transorbital. The included articles were analyzed. In addition, the references list of the included papers was searched for further articles.

Results

Studies based on the endoscopic endonasal and transorbital approach have emphasized that it is minimally invasive; on the other hand, it offers an advantage to maximal resection success in the case of skull base tumors with advanced endoscopic skills. Transorbital neuroendoscopic surgery was criticized for being highly technical and narrow in its scope, with reduced morbidity. Superior Eyelid Approach involves a direct access with hidden incisions, potential for eyelid complications. Lateral orbitotomy entailed some inherent risks, such as muscle and nerve injury, but it gave excellent exposure to lesions that are lateral in the orbit. The transorbital endoscopic intraconal approach and the transconjunctival approach give direct advantages but are, however, limited to the type of lesion and location.

Conclusion

The main technique focused on in this overview is the approaches through orbits, which greatly contribute to further innovation brought into the surgical panorama of skull base interventions. All such techniques do have their characteristics and applications, keeping them moving toward less invasiveness.

360 Degrees Endoscopic Access to and Through the Orbit

The treatment of pathologies located within and surrounding the orbit poses considerable surgical challenges, due to the intricate presence of critical neurovascular structures in such deep, confined spaces. Historically, transcranial and craniofacial approaches have been widely employed to deal with orbital pathologies. However, recent decades have witnessed the emergence of minimally invasive techniques aimed at reducing morbidity. Among these techniques are the endoscopic endonasal approach and the subsequently developed endoscopic transorbital approach (ETOA), encompassing both endonasal and transpalpebral approaches. These innovative methods not only facilitate the management of intraorbital lesions but also offer access to deep-seated lesions within the anterior, middle, and posterior cranial fossa via specific transorbital and endonasal corridors. Contemporary research indicates that ETOAs have demonstrated exceptional outcomes in terms of morbidity rates, cosmetic results, and complication rates. This study aims to provide a comprehensive description of endoscopic-assisted techniques that enable a 360° access to the orbit and its surrounding regions. The investigation will delve into indications, advantages, and limitations associated with different approaches, while also drawing comparisons between endoscopic approaches and traditional microsurgical transcranial approaches.

Endoscopic transorbital resection of the temporal lobe: anatomic qualitative and quantitative study

Objective

Starting from an anatomic study describing the possibility of reaching the temporal region through an endoscopic transorbital approach, many clinical reports have now demonstrated the applicability of this strategy when dealing with intra-axial lesions. The study aimed to provide both a qualitative anatomic description of the temporal region, as seen through a transorbital perspective, and a quantitative analysis of the amount of temporal lobe resection achievable via this route.

Material and methods

A total of four cadaveric heads (eight sides) were dissected at the Laboratory of Surgical Neuroanatomy (LSNA) of the University of Barcelona, Spain. A stepwise description of the resection of the temporal lobe through a transorbital perspective is provided. Qualitative anatomical descriptions and quantitative analysis of the amount of the resection were evaluated by means of pre- and post-dissection CT and MRI scans, and three-dimensional reconstructions were made by means of BrainLab®Software.

Results

The transorbital route gives easy access to the temporal region, without the need for extensive bone removal. The resection of the temporal lobe proceeded in a subpial fashion, mimicking what happens in a surgical scenario. According to our quantitative analysis, the mean volume removed was 51.26%, with the most superior and lateral portion of the temporal lobe being the most difficult to reach.

Conclusion

This anatomic study provides qualitative and quantitative details about the resection of the temporal lobe via an endoscopic transorbital approach. Our results showed that the resection of more than half of the temporal lobe is possible through this surgical corridor. While the anterior, inferior, and mesial portions of the temporal lobe were easily accessible, the most superior and lateral segment was more difficult to reach and resect. Our study serves as an integration to the current anatomic knowledge and clinical practice knowledge highlighting and also as a starting point for further anatomic studies addressing more selected segments of the temporal lobe, i.e., the mesial temporal region.

Through the orbit and beyond: Current state and future perspectives in endoscopic orbital surgery on behalf of the EANS frontiers committee in orbital tumors and the EANS skull base section

Introduction

Orbital surgery has always been disputed among specialists, mainly neurosurgeons, otorhinolaryngologists, maxillofacial surgeons and ophthalmologists. The orbit is a borderland between intra- and extracranial compartments; Krönlein's lateral orbitotomy and the orbitozygomatic infratemporal approach are the historical milestones of modern orbital-cranial surgery.

Research question

Since its first implementation, endoscopy has significantly impacted neurosurgery, changing perspectives and approaches to the skull base. Since its first application in 2009, transorbital endoscopic surgery opened the way for new surgical scenario, previously feasible only with extensive tissue dissection.

Material and methods

A PRISMA based literature search was performed to select the most relevant papers on the topic.

Results

Here, we provide a narrative review on the current state and future trends in endoscopic orbital surgery.

Discussion and conclusion

This manuscript is a joint effort of the EANS frontiers committee in orbital tumors and the EANS skull base section.

Transuncal Selective Amygdalohippocampectomy by an Inferolateral Preseptal Endoscopic Approach Through Inferior Eyelid Conjunctival Incision: An Anatomic Study

BACKGROUND

Transorbital endoscopic approaches have been described for pathologies of anterior and middle fossae. Standard lateral orbitotomy gives access to mesial temporal lobe, but the axis of work is partially obscured by the temporal pole and working corridor is limited.

OBJECTIVE

To evaluate the usefulness of an inferolateral orbitotomy to provide a more direct corridor to perform a transuncal selective amygdalohippocampectomy.

METHODS

Three adult cadaveric specimens were used for a total of 6 dissections. A step-by-step description and illustration of the transuncal corridor for a selective amygdalohippocampectomy were performed using the inferolateral orbitotomy through an inferior eyelid conjunctival incision. The anatomic landmarks were demonstrated in detail. Orbitotomies and angles of work were measured from computed tomography scans, and the area of resection was illustrated by postdissection MRI.

RESULTS

Inferior eyelid conjunctival incision was made for exposure of the inferior orbital rim. Inferolateral transorbital approach was performed to access the transuncal corridor. Endoscopic selective amygdalohippocampectomy was performed through the entorhinal cortex without damage to the temporal neocortex or Meyer's loop. The mean horizontal diameter of the osteotomy was 14.4 mm, and the vertical one was 13.6 mm. The mean angles of work were 65° and 35.5° in the axial and sagittal planes, respectively. Complete amygdalohippocampectomy was achieved in all 6 dissections.

CONCLUSION

Transuncal selective amygdalohippocampectomy was feasible in cadaveric specimens using the inferolateral transorbital endoscopic approach avoiding damage to the temporal neocortex and Meyer's loop. The inferior eyelid conjunctival incision may result in an excellent cosmetic outcome.

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.

A Frontal Route to Middle and Posterior Cranial Fossa: Quantitative Study for the Lateral Transorbital Endoscopic Approach and Comparison with the Subtemporal Approach

BACKGROUND

Skull base lesions within the middle cranial fossa (MCF) remain challenging. Recent reports suggest that transorbital endoscopic approaches (TOEAs) might be particularly suitable to access the MCF and expose the lateral wall of the cavernous sinus and the Meckel's cave.

METHODS

The present study was developed to compare the nuances of the subtemporal approach (STA) with those of the lateral TOEA (LTOEA) to the MCF and posterior cranial fossa (PCF) in cadaveric specimens. After orbital craniectomy, interdural opening of the cavernous sinus lateral wall (CSlw), exposure of the Gasserian ganglion, and extradural elevation of the temporal lobe was performed. Next, anterior endoscopic petrosectomy was performed and the PCF was accessed. We quantitatively analyzed and compared the angles of attack and distances between LTOEA and STA to different structures at the CSlw, petrous apex (PA), and PCF.

RESULTS

Cadaveric dissection through the LTOEA completely exposed the CSlw and PA. LTOA exhibited larger distances than the STA to all targets. Importantly, these differences were greater at the PA and its surrounding key anatomic landmarks. The horizontal and vertical angles of attack allowed by the LTOA were smaller both for the CSlw and PA. However, these differences were not significant for the vertical angle of attack at the CSlw.

CONCLUSIONS

LTOEA provides a direct ventral route to the medial aspect of MCF, PA, and PCF. Although TOEAs are versatile approaches, the unfamiliar surgical anatomy and limited instrument maneuverability demand extensive cadaveric dissection before moving to the clinical setting.

Endoscopic-assisted transorbital surgery: Where do we stand on the scott’s parabola? personal considerations after a 10-year experience

Transorbital approaches are genuinely versatile surgical routes which show interesting potentials in skull base surgery. Given their “new” trajectory, they can be a very useful adjunct to traditional routes, even being a valid alternative to them in some cases, and add valuable opportunities in selected patients. Indications are constantly expanding, and currently include selected intraorbital, skull base and even intra-axial lesions, both benign and malignant. Given their relatively recent development and thus unfamiliarity among the skull base community, achieving adequate proficiency needs not only a personalized training and knowledge but also, above all, an adequate case volume and a dedicated setting. Current, but mostly future, applications should be selected by genetic, omics and biological features and applied in the context of a truly multidisciplinary environment.

Endoscopic Transorbital Approach to Mesial Temporal Lobe for Intra-Axial Lesions: Cadaveric Study and Case Series (SevEN-008)

BACKGROUND

Endoscopic transorbital approach (ETOA) has been proposed as a minimally invasive technique for the treatment of skull base lesions located around mesial temporal lobe (MTL), mostly extra-axial pathology.

OBJECTIVE

To explore the feasibility of ETOA in accessing intraparenchymal MTL with cadaveric specimens and describe our initial clinical experience of ETOA for intra-axial lesions in MTL.

METHODS

Anatomic dissections were performed in 4 adult cadaveric heads using a 0° endoscope. First, a stepwise anatomical investigation of ETOA to intraparenchymal MTL was explored. Then, ETOA was applied clinically for 7 patients with intra-axial lesions in MTL, predominantly high-grade gliomas (HGGs) and low-grade gliomas (LGGs).

RESULTS

The extradural stage of ETOA entailed a superior eyelid incision followed by orbital retraction, drilling of orbital roof, greater and lesser wing of sphenoid bone, and cutting of the meningo-orbital band. For the intradural stage, the brain tissue medial to the occipito-temporal gyrus was aspirated until the temporal horn was opened. The structures of MTL could be aspirated selectively in a subpial manner without injury to the neurovascular structures of the ambient and sylvian cisterns, and the lateral neocortex. After cadaveric validation, ETOA was successfully performed for 4 patients with HGGs and 3 patients with LGGs. Gross total resection was achieved in 6 patients (85.7%) without significant surgical morbidities including visual field deficits.

CONCLUSION

ETOA provides a logical line of access for intra-axial lesions in MTL. The safe and natural surgical trajectory of ETOA can spare brain retraction, neurovascular injury, and disruption of the lateral neocortex.

Transorbital Neuroendoscopic Surgery as a Mainstream Neurosurgical Corridor: A Systematic Review

BACKGROUND

Transorbital neuroendoscopic surgery (TONES) offers a new level of minimally invasive, minimally disfiguring skull base surgery with maximal surgical visualization.

METHODS

This review systematically assesses the body of published anatomic (cadaveric) and clinical evidence for the approach. PubMed, Cochrane Library, Ovid MEDLINE, and Embase were systematically searched for articles in which the TONES surgical technique was used in an anatomic, clinical, or combined study. The outcomes of interest included identification of the diseases, operative outcomes, and complication rates.

RESULTS

Twenty-three articles were selected for this systematic review: 10 were purely anatomic, 10 were clinical, and 3 had both clinical and cadaveric components. The articles reported 69 patients undergoing transorbital or combined transorbital and transnasal intervention. A total of 30 cases of cerebrospinal fluid leak were documented; of these, 28 (93%) had successful resolution, 2 (7%) had recurrence, and 5 (15%) experienced complications. A total of 31 tumors were biopsied (n = 1), resected (n = 22), or debulked (n = 8). Meningiomas were the most common lesion managed via TONES, with 5 of 7 patients with meningioma who reported preoperative neurologic deficits experiencing an improvement in extraocular movement impairment, visual acuity, proptosis, and ptosis. Transient postoperative clinical sequelae, including diplopia and ptosis, were increasingly associated with the superior lid crease incision and the sole transorbital approach.

CONCLUSIONS

TONES is a significant development in transorbital skull base surgery. However, comprehensive, robust, comparative analyses and increasing use and generalizability of this technique in skull base surgery are awaited.

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.

The Role of the Transorbital Superior Eyelid Approach in the Management of Selected Spheno-orbital Meningiomas: In-Depth Analysis of Indications, Technique, and Outcomes from the Study of a Cohort of 35 Patients

Objective Primary goal in spheno-orbital meningioma (SOM) surgery still remains complete resection. Nevertheless, given their highly infiltrative nature, a growing body of literature suggests to shift toward function-sparing surgeries. We here present our experience in the management of SOMs through the endoscopic superior eyelid approach (SEA).

Methods Surgical database from our multidisciplinary work group was retrospectively reviewed to identify patients treated for SOMs in the last 10 years by our senior authors, analyzing and correlating clinical, radiological, and outcome variables among the different approaches used.

Results There were 35 patients (mean age of 57.3 ± 12.86 years), with a mean follow-up of 31.5 months (range: 6–84 months). The most common preoperative complaint was proptosis (62.9%) followed by diplopia and visual deficit. Greater and lesser sphenoid wings were the areas mainly involved by the pathology (91.4% and 88.6%, respectively), whereas orbital invasion was evidenced in one-third of cases. Patients were operated on through craniotomic (48.6%), endoscopic superior eyelid (37.1%), and combined cranioendoscopic (14.3%) approaches. Simpson grades 0 to II were accomplished in 46.2% of SEA and 76.5% of craniotomies. All patients with a preoperative visual deficit improved in the postoperative period, independently from the approach used. On patients who underwent endoscopic SEA, there was improved their short-/long-term postoperative Karnofsky Performance Status.

Conclusions Endoscopic SEA is a safe and effective alternative to transcranial approaches in very selected cases of SOMs, where the planned primary objective was to obtain a maximally safe resection, aimed at symptom relief, rather than a gross total resection at any cost.

Surgery around the Orbit: How to Select an Approach

Orbital region pathologies may be safely and effectively treated through a various number of approaches. As the concept of "outcome" and minimally invasive surgery keeps gaining popularity in neurosurgery, these approaches-each with specific indications and limitations-together provide the best surgical options.

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.

Endoscopic endo- and extra-orbital corridors for spheno-orbital region: anatomic study with illustrative case

BACKGROUND AND OBJECTIVE

Management of selected spheno-orbital meningiomas via the endoscopic transorbital route has been reported. Surgical maneuverability in a narrow corridor as that offered by the orbit may be challenging. We investigate the additional use of an extra-orbital (EXO) path to be used in combination with the endo-orbital (EO) corridor.

MATERIAL AND METHODS

Three human cadaveric heads (six orbits) were dissected at the Laboratory of Surgical Neuroanatomy at the University of Barcelona. The superior eyelid endoscopic transorbital approach was adopted, introducing surgical instruments via both corridors. Surgical freedom analysis was run to determine directionality of each corridor and to calculate the surgical maneuverability related to three anatomic targets: superior orbital fissure (SOF), foramen rotundum (FR), and foramen ovale (FO). We also reported of a 37-year-old woman with a spheno-orbital meningioma with hyperostosis of the lateral wall of the right orbit, treated with such combined endo-orbital and extra-orbital endoscopic approach.

RESULTS

Combining both endo-orbital and extra-orbital corridors permitted a greater surgical freedom for all the targets compared with the surgical freedom of each corridor alone (EO + EXO to SOF: 3603.8 mm² ± 2452.5 mm²; EO + EXO to FR: 1533.0 mm² ± 892.2 mm²; EO + EXO to FO: 1193.9 mm² ± 782.6 mm²). Analyzing the extra-orbital pathway, our results showed that the greatest surgical freedom was gained in the most medial portion of the considered area, namely the SOF (1180.5 mm² ± 648.3 mm²). Regarding the surgical case, using both pathways, we gained enough maneuverability to nearly achieve total resection with no postoperative complications.

CONCLUSION

An extra-orbital corridor may be useful to increase the instruments' maneuverability, during a pure endoscopic superior eyelid approach, and to reach the most medial portion of the surgical field from a lateral-to-medial trajectory. Further studies are needed to better define the proper indications for such strategy.

Presurgical simulation for neuroendoscopic procedures: Virtual study of the integrity of neurological pathways using diffusion tensor imaging tractography

Background:

White matter (WM) transgression is an unexplored concept in neuroendoscopy. Diffusion tensor image (DTI) tractography could be implemented as a planning and postoperative evaluation tool in functional disconnection procedures (FDPs), which are, currently, the subject of technological innovations. We intend to prove the usefulness of this planning method focused on the assessment of WM injury that is suitable for planning FDPs.

Methods:

Ten cranial magnetic resonance studies (20 sides) without pathological findings were processed. Fascicles were defined by two regions of interest (ROIs) using the fiber assignment method by the continuous tracking approach. Using three-dimensional (3D) simulation and DTI tractography, we created an 8-mm virtual endoscope and an uninjured inferior fronto-occipital fasciculus (IFOF) from two ROIs. The injured tract was generated using a third ROI built from the 3D model of the intersection of the oriented trajectory of the endoscope with the fascicle. Data and images were quantitatively and qualitatively analyzed.

Results:

The average percentage of the injured fibers was 32.0% (range: 12.4%–70%). The average intersected volume was 1.1 cm³ (range: 0.3–2.3 cm³). Qualitative analysis showed the inferior medial quadrant of the inferior fronto-occipital fasciculus (IFOF) as the most frequently injured region. No hemispherical asymmetry was found (P > 0.5).

Conclusion:

DTI tractography is a useful surgical planning tool that could be implemented in several endoscopic procedures. Together with a functional atlas, the presented technique provides a noninvasive method to assess the potential sequelae and thus to optimize the surgical route. The suggested method could be implemented to analyze pathological WM fascicles and to assess the surgical results of FDP such as hemispherotomy or amygdalohippocampectomy. More studies are needed to overcome the limitations of the tractography based information and to develop more anatomically and functionally reliable planning systems.

Endoscopic transorbital transtentorial approach to middle incisural space: preclinical cadaveric study

BACKGROUND

Endoscopic transorbital approach is a novel development of minimally invasive skull base surgery. Recently, anatomical studies have started to discuss the expanded utilization of endoscopic transorbital route for intracranial intradural lesions. The goal of this cadaveric study is to assess the feasibility of endoscopic transorbital transtentorial approach for exposure of middle incisural space.

METHODS

Anatomical dissections were performed in four human cadaveric heads (8 sides) using 0- and 30-degree endoscopes. A stepwise description of endoscopic transorbital transtentorial approach to middle incisural space and related anatomy was provided.

RESULTS

Orbital manipulation following superior eyelid crease incision with lateral canthotomy and cantholysis established space for bone drilling. Extradural stage consisted of extensive drilling of orbital roof of frontal bone, lessor, and greater wings of sphenoid bone. Intradural stage was composed of dissection of sphenoidal compartment of Sylvian fissure, lateral mobilization of mesial temporal lobe, and penetration of tentorium. A cross-shaped incision of tentorium provided direct visualization of crural cistern with anterolateral aspect of cerebral peduncle and upper pons. Interpeduncular cistern, prepontine cistern, and anterior portions of ambient and cerebellopontine cisterns were exposed by 30-degree endoscope.

CONCLUSION

The endoscopic transorbital transtentorial approach can be used as a minimally invasive surgery for exposure of middle incisural space. Extensive drilling of sphenoid wing and lateral mobilization of mesial temporal lobe are the main determinants of successful dissection. Further studies are needed to confirm the clinical feasibility of this novel approach.

Comparative Analysis of the Exposure and Surgical Freedom of the Endoscopic Extended Minipterional Craniotomy and the Transorbital Endoscopic Approach to the Anterior and Middle Cranial Fossae

BACKGROUND

Numerous minimally invasive approaches to the skull base have been successively developed. Knowledge of the surgical nuances of a specific approach may facilitate approach selection. This study sought to compare the nuances of an extended version of the minipterional craniotomy (EMPT) with those of the transorbital endoscopic approach (TOEA) to the anterior and middle cranial fossae (ACF and MCF, respectively).

OBJECTIVE

To quantitatively analyze and compare the area of exposure and surgical freedom between EMPT and TOEA to the ACF and MCF.

METHODS

EMPT and TOEA were carried out in 5 latex-injected cadaveric heads, bilaterally (10 sides). For each approach, the area of exposure, surgical freedom, and angle of attack were obtained with neuronavigation and statistically compared.

RESULTS

No significant difference was found between the mean area of exposure of EMPT and TOEA at the ACF and MCF (P = .709 and .317, respectively). The mean exposure area at the ACF was of 13.4 ± 2.6 cm2 (mean ± standard deviation) and 13.0 ± 1.9 cm2 for EMPT and TOEA, respectively. Except for the crista galli, EMPT afforded a larger area of surgical freedom at all targets. EMPT also achieved significantly greater attack angles in vertical axis except to the crista galli. The horizontal attack angles to all targets were similar between approaches.

CONCLUSION

EMPT and TOEA offer a comparable area of exposure at the ACF and MCF in the cadaver; however, the instrument maneuverability afforded by EMPT is superior. Further studies are necessary to better define their precise surgical application.

Endoscopic extradural supraorbital approach to the temporal pole and adjacent area: technical note

The authors’ initial experience with the endoscopic extradural supraorbital approach to the temporal pole and adjacent area is reported. Fully endoscopic surgery using the extradural space via a supraorbital keyhole was performed for tumors in or around the temporal pole, including temporal pole cavernous angioma, sphenoid ridge meningioma, and cavernous sinus pituitary adenoma, mainly using 4-mm, 0° and 30° endoscopes and single-shaft instruments. After making a supraorbital keyhole, a 4-mm, 30° endoscope was advanced into the extradural space of the anterior cranial fossa during lifting of the dura mater. Following identification of the sphenoid ridge, orbital roof, and anterior clinoid process, the bone lateral to the orbital roof was drilled off until the dura mater of the anterior aspect of the temporal lobe was exposed. The dura mater of the temporal lobe was incised and opened, exposing the temporal pole under a 4-mm, 0° endoscope. Tumors in or around the temporal pole were safely removed under a superb view through the extradural corridor. The endoscopic extradural supraorbital approach was technically feasible and safe. The anterior trajectory to the temporal pole using the extradural space under endoscopy provided excellent visibility, allowing minimally invasive surgery. Further surgical experience and development of specialized instruments would promote this approach as an alternative surgical option.

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 < .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.

Skull Base Trauma: Clinical Considerations in Evaluation and Diagnosis and Review of Management Techniques and Surgical Approaches

Traumatic injuries to the skull base can involve critical neurovascular structures and present with symptoms and signs that must be recognized by physicians tasked with management of trauma patients. This article provides a review of skull base anatomy and outlines demographic features in skull base trauma. The manifestations of various skull base injuries, including CSF leaks, facial paralysis, anosmia, and cranial nerve injury, are discussed, as are appropriate diagnostic and radiographic testing in patients with such injuries. While conservative management is sometimes appropriate in skull base trauma, surgical access to the skull base for reconstruction of traumatic injuries may be required. A variety of specific surgical approaches to the anterior cranial fossa are discussed, including the classic anterior craniofacial approach as well as less invasive and newer endoscope-assisted approaches to the traumatized skull base.

Transorbital endoscopic approach for exposure of the sylvian fissure, middle cerebral artery and crural cistern: an anatomical study

BACKGROUND

The availability of minimal access instrumentation and endoscopic visualization has revolutionized the field of minimally invasive skull base surgery. The transorbital endoscopic approach using an eyelid incision has been proposed as a new minimally invasive technique for the treatment of skull base pathology, mostly extradural tumors. Our study aims to evaluate the anatomical aspects and potential role of the transorbital endoscopic approach for exposure of the sylvian fissure, middle cerebral artery and crural cistern.

METHODS

An anatomical dissection was performed in four freshly injected cadaver heads (8 orbits) using 0- and 30-degree endoscopes. First, an endoscopic endonasal medial orbital decompression was done to facilitate medial retraction of the orbit. An endoscopic transorbital approach through an eyelid incision, with drilling of the posterior wall of the orbit and lesser sphenoidal wing, was then performed to expose the sylvian fissure and crural cisterns. A stepwise anatomical description of the approach and visualized anatomy is detailed.

RESULTS

A superior eyelid incision followed by orbital retraction provided a surgical window of approximately 1.2 cm (range 1.0-1.5 cm) for endoscopic transorbital dissection. The superior (SOF) and inferior (IOF) orbital fissures represent the medial limits of the approach and are identified in the initial part of the procedure. Drilling of the orbital roof (lateral and superior to the SOF), greater sphenoidal wing (lateral to the SOF and IOF) and lesser sphenoidal wing exposed the anterior and middle fossa dura. A square-shaped dural opening provided visualization of the posterior orbital gyri, sylvian fissure and temporal pole. Intradural dissection allowed exposure of the sphenoidal portion of the sylvian fissure, M1, MCA bifurcation and M2 branches and lenticulostriate perforators. Dissection of the medial aspect of the sylvian and carotid cisterns with a 30-degree endoscope allowed exposure of the mesial temporal lobe and crural cistern.

CONCLUSIONS

The transorbital endoscopic approach allows successful exposure of the sphenoidal portion of the sylvian fissure and M1 and M2 segments of the middle cerebral artery. Angled endoscopes may provide visualization of the mesial temporal lobe and crural cistern. Although our anatomical study demonstrates the feasibility of intradural dissection and closure via an endoscopic transorbital approach, further studies are necessary to evaluate its role in the clinical scenario.

Laser Interstitial Thermal Therapy for Mesial Temporal Lobe Epilepsy

Approximately one-third of patients with epilepsy do not achieve adequate seizure control through medical management alone. Mesial temporal lobe epilepsy (MTLE) is one of the most common forms of medically refractory epilepsy referred for surgical management. Stereotactic laser amygdalohippocampotomy using magnetic resonance-guided laser interstitial thermal therapy (MRg-LITT) is an important emerging therapy for MTLE. Initial published reports support MRg-LITT as a less invasive surgical option with a shorter hospital stay and fewer neurocognitive side effects compared with craniotomy for anterior temporal lobectomy with amygdalohippocampectomy and selective amygdalohippocampectomy. We provide a historical overview of laser interstitial thermal therapy development and the technological advancements that led to the currently available commercial systems. Current applications of MRg-LITT for MTLE, reported outcomes, and technical issues of the surgical procedure are reviewed. Although initial reports indicate that stereotactic laser amygdalohippocampotomy may be a safe and effective therapy for medically refractory MTLE, further research is required to establish its long-term effectiveness and its cost/benefit profile.

The evolving role of the oculoplastic surgeon in skull base surgery

PURPOSE OF REVIEW

Classical orbital approaches in skull base surgery have involved large incisions with extensive bone removal resulting in prolonged recovery with associated morbidity and mortality. The purpose of this review is to explore recent advances in skull base surgery that are applicable to the orbital surgeon.

RECENT FINDINGS

Transnasal endoscopic surgery provides access to the medial 180 degrees of the orbit. Access to the lateral 180 degrees may be obtained using transmaxillary and transcranial techniques. Transorbital approaches and multiport techniques further expand the reach of the skull base surgeon. These minimally invasive techniques are supplanting the classical pterional, frontotemporal, frontotemporal orbitozygomatic, frontal, and subfrontal approaches.

SUMMARY

The role of the orbital surgeon in skull base surgery is changing. Transnasal and transcranial approaches to orbital disorders using minimally invasive techniques are becoming more common. In addition, transorbital access to the skull base, paranasal sinuses, and anterior and middle cranial fossa is offering new opportunities for the orbital surgeon.

The Inferolateral Transorbital Endoscopic Approach: A Preclinical Anatomic Study

BACKGROUND

In recent years, transorbital endoscopic approaches are increasing in popularity as they provide several corridors to reach lateral areas of the ventral skull base through the orbit. The aim of this study is to investigate the feasibility of the inferolateral transorbital endoscopic approach (ILTEA) by detailing the step-by-step dissection, anatomic landmarks, and target anatomic areas.

METHODS

Seven cadaveric specimens (14 sides) were dissected in the Laboratory of Endoscopic Anatomy of the University of Brescia. Step-by-step dissection of ILTEA was performed to identify the main anatomic landmarks and corridors. Skin incision, dural incision, and boundaries of craniectomy were measured. Neuronavigation was used to check landmarks, track boundaries of surgical volumes, and measure orbital dislocation.

RESULTS

The study on the 14 ILTEAs defined 1 anatomic area ("waterline door") that leads to 4 corridors: Meckel's cave corridor, carotid foramen corridor, petrous corridor, and transdural middle fossa corridor. Crucial anatomic landmarks were identified and analyzed. Orbital dislocation was <10 mm.

CONCLUSIONS

ILTEA provides the surgeon with a direct route to the region of the "waterline door," lateral areas of the ventral skull base, and middle cranial fossa. In addition, it allows an optimal view of the intracranial and extracranial portions of the maxillary and mandibular nerves. Further anatomic and clinical studies are needed to validate ILTEA in surgical practice.