Anterior clinoidectomy in low lying internal carotid artery-posterior communicating artery aneurysm.

BACKGROUND: At times, a regulation internal carotid artery-posterior communicating artery junction (ICA-P-Comm) aneurysm becomes a surgical hurdle owing to its close proximity to the anterior clinoid process, an immovable ICA and a concealed dominant P-Comm artery arising from the aneurysm neck. METHOD: A 70 year old patient with a low lying ICA-P-Comm aneurysm underwent a "tailored" intradural clinoidectomy for aneurysm clipping. CONCLUSION: A tailored anterior clinoidectomy to expose "just enough" allows a proximal ICA control in a suitable area, mobility of an atherosclerotic ICA and exposes the P-Comm artery origin which are essential in safe clipping of these aneurysms.

HOW I DO IT: Cushing's disease-selective adenomectomy via an endoscopic transsphenoidal approach.

BACKGROUND: An ACTH-secreting pituitary adenoma is the most common cause of excessive endogenous glucocorticoid production resulting in Cushing's Syndrome. A multidisciplinary approach is paramount. Selective adenomectomy is the treatment of choice. METHOD: Endoscopic transnasal transsphenoidal approach to the tumour, along with techniques for resection, are demonstrated. CONCLUSION: Endoscopic transsphenoidal approaches with its magnified view of the pituitary gland allows precise microsurgical dissection during selective adenomectomy. This technique increases the possibility of proving a gross total resection, leading to clinical and biochemical cure in these patients.

Endoscopic Endonasal Transsphenoidal Surgery for Intrasellar Mixed Germ Cell Tumors.

A mixed germ cell tumor (MGCT) in the neurohypophysis is very rare, with only a few reported cases1-4 but none with surgical videos. In this report, the endoscopic endonasal transsphenoidal approach for MGCT in the neurohypophysis is presented (Video 1). A 12-year-old girl with ocular pain, fatigue, and nausea presented with gradual onset of quadrant hemianopsia and left oculomotor palsy. Magnetic resonance imaging showed an enhanced mass in the sella turcica with multiple components involving the pituitary gland and stalk. Her endocrinological examination showed decreased levels of pituitary hormones and simultaneously elevated serum levels of alpha-fetoprotein and beta-human chorionic gonadotropin. After pituitary hormone replacement, endoscopic endonasal transsphenoidal surgery was planned. The tumor was strongly adherent to the surrounding structures, and gross total resection was achieved. The histological diagnosis was MGCT with a teratoma component. Postoperatively, her vision and oculomotor palsy improved swiftly, and adjuvant chemotherapy and radiotherapy were administered. In this case, 3-dimensional computer graphics were created from the preoperative computed tomography and magnetic resonance imaging studies. Preoperative simulation with the 3-dimensional computer graphic images and intraoperative verification with indocyanine green images facilitated our understanding of the surrounding anatomy, including the tumor components, pituitary gland, and internal carotid arteries.5 After removal of the tumor, multilayer fascial closure was performed for skull base reconstruction.6 MGCT in the neurohypophysis can be strongly adherent to the surrounding structures, requiring careful dissection and resection under endoscopy. At the last follow-up (8 months after surgery), the tumor was successfully controlled, and the patient had no neurological symptoms with pituitary hormone replacement therapy.

Proposing a sphenoid bone quality score: a novel concept for transsphenoidal surgery.

Transsphenoid surgery is a common procedure for removing pituitary and other sellar tumors. The quality and density of the sphenoid bone, which serves as the access route to the sellar region, can affect the surgical outcomes and complications. However, there is no standardized method to assess sphenoid bone quality. I propose a sphenoid bone quality score, based on criteria and parameters derived from preoperative imaging techniques. This score could provide information on the bone characteristics and challenges of each case, and help to select the optimal surgical approach, instruments, grafts, and measures. This score could also enable a consistent evaluation of the surgery and the outcomes, and facilitate the communication and collaboration among different medical disciplines.

Endoscopic transorbital approach bone pillars: a comprehensive stepwise anatomical appraisal.

OBJECTIVE: The endoscopic superior eyelid transorbital approach has garnered significant consideration and gained popularity in recent years. Detailed anatomical knowledge along with clinical experience has allowed refinement of the technique as well as expansion of its indications. Using bone as a consistent reference, the authors identified five main bone pillars that offer access to the different intracranial targeted areas for different pathologies of the skull base, with the aim of enhancing the understanding of the intracranial areas accessible through this corridor. METHODS: The authors present a bone-oriented review of the anatomy of the transorbital approach in which they conducted a 3D analysis using Brainlab software and performed dry skull and subsequent cadaveric dissections. RESULTS: Five bone pillars of the transorbital approach were identified: the lesser sphenoid wing, the sagittal crest (medial aspect of the greater sphenoid wing), the anterior clinoid, the middle cranial fossa, and the petrous apex. The associations of these bone targets with their respective intracranial areas are reported in detail. CONCLUSIONS: Identification of consistent bone references after the skin incision has been made and the working space is determined allows a comprehensive understanding of the anatomy of the approach in order to safely and effectively perform transorbital endoscopic surgery in the skull base.

Endoscopic precaruncular medial transorbital and endonasal multiport approaches to the contralateral skull base: a clinicoanatomical study.

OBJECTIVE: Minimally invasive endoscopic endonasal multiport approaches create additional visualization angles to treat skull base pathologies. The sublabial contralateral transmaxillary (CTM) approach and superior eyelid lateral transorbital approach, frequently used nowadays, have been referred to as the "third port" when used alongside the endoscopic endonasal approach (EEA). The endoscopic precaruncular contralateral medial transorbital (cMTO) corridor, on the other hand, is an underrecognized but unique port that has been used to repair CSF rhinorrhea originating from the lateral sphenoid sinus recess. However, no anatomical feasibility studies or clinical experience exists to assess its benefits and demonstrate its potential role in multiport endoscopic access to the other contralateral skull base areas. In this study, the authors explored the application and potential utility of multiport EEA combined with the endoscopic cMTO approach (EEA/cMTO) to three target areas of the contralateral skull base: lateral recess of sphenoid sinus (LRSS), petrous apex (PA) and petroclival region, and retrocarotid clinoidocavernous space (CCS). METHODS: Ten cadaveric specimens (20 sides) were dissected bilaterally under stereotactic navigation guidance to access contralateral LRSS via EEA/cMTO. The PA and petroclival region and retrocarotid CCS were exposed via EEA alone, EEA/cMTO, and EEA combined with the sublabial CTM approach (EEA/CTM). Qualitative and quantitative assessments, including working distance and visualization angle to the PA, were recorded. Clinical application of EEA/cMTO is demonstrated in a lateral sphenoid sinus CSF leak repair. RESULTS: During the qualitative assessment, multiport EEA/cMTO provides superior visualization from a high vantage point and better instrument maneuverability than multiport EEA/CTM for the PA and retrocarotid CCS, while maintaining a similar lateral trajectory. The cMTO approach has significantly shorter working distances to all three target areas compared with the CTM approach and EEA. The mean distances to the LRSS, PA, and retrocarotid CCS were 50.69 ± 4.28 mm (p < 0.05), 67.11 ± 5.05 mm (p < 0.001), and 50.32 ± 3.6 mm (p < 0.001), respectively. The mean visualization angles to the PA obtained by multiport EEA/cMTO and EEA/CTM were 28.4° ± 3.27° and 24.42° ± 5.02° (p < 0.005), respectively. CONCLUSIONS: Multiport EEA/cMTO to the contralateral LRSS offers the advantage of preserving the pterygopalatine fossa contents and the vidian nerve, which are frequently sacrificed during a transpterygoid approach. This approach also offers superior visualization and better instrument maneuverability compared with EEA/CTM for targeting the petroclival region and retrocarotid CCS.

Optimizing the Endoscopic Transorbital Approach: MacCarty Keyhole for Enhanced Surgical Exposure in the Opticocarotid Region.

BACKGROUND: In recent years, the endoscopic transorbital (TO) approach has gained increasing interest for the treatment of middle cranial fossa lesions. We propose a technical refinement to the conventional superior eyelid TO approach, which improves the surgical exposure and augments the working angles when targeting the opticocarotid region. METHODS: Four embalmed adult cadaveric specimens (8 sides) were dissected at the Laboratory of Surgical Neuroanatomy of our institution. A TO approach was performed, with removal of the anterior clinoid process and the lateral orbital rim. Subsequently, the MacCarty keyhole was drilled in the superolateral orbital wall. Given that the lesser sphenoid wing was already drilled in the conventional TO craniectomy, the opening of the keyhole was essentially a lateral extension of the craniectomy. RESULTS: The procedure was successfully conducted in all 4 orbits. Clinoidectomy was performed either before or after extending the craniectomy to the MacCarty point. Extending the craniectomy made anterior clinoidectomy easier, by increasing the surgical exposure, and allowing a more lateral entrance for the endoscope. The extension also facilitated frontal lobe retraction, and it facilitated the optic nerve and carotid artery manipulation. Postoperative computed tomography scans showed a minimal 10-mm craniectomy extension, which remained covered by the temporal muscle after reconstruction. CONCLUSIONS: The modified endoscopic TO approach with the extension of the craniectomy to MacCarty point improves surgical access and visualization of the opticocarotid region. This facilitates anterior clinoidectomy and optic nerve decompression. Although it implies judicious instrument manipulation and a larger incision size, further studies can define its potential benefits.

Identifying an optimal approach for the placement of pterygoid implants: A 3D finite element analysis.

STATEMENT OF PROBLEM: A consensus on the optimal approach to the placement of pterygoid implants is lacking. PURPOSE: The purpose of this finite element analysis study was to determine the optimal approach to the placement of pterygoid implants by comparing biomechanical behavior. MATERIAL AND METHODS: An edentulous and moderately atrophic maxilla with the anatomic structure of the pterygomaxillary region was constructed. Complete arch restorations with 4 standard anterior implants and pterygoid implants in 3 approaches were simulated: L70, long pterygoid implants (4.1×18 mm) inclined at 70 degrees relative to the Frankfort horizontal plane with anchorage in the pterygoid process; L45, long pterygoid implants (4.1×20 mm) inclined at 45 degrees with anchorage in the pterygoid process; and S45, shorter pterygoid implants (4.1×13 mm) inclined 45 degrees without apical anchorage. The L70, L45, and S45 groups were classified as D or S depending on the bone quality: D3 (dense trabecular bone) or D4 (sparse trabecular bone). A total of 6 finite element models were built. The bone failure theory, based on the von Mises theory, was used to judge yielding of the trabecular bone. The von Mises stress (σVM) distribution was measured in the cortical bone, the trabecular bone, and on the implant surface. Deformation (DF) distribution was obtained for the entire bone (DFB) and bone surrounding the pterygoid implant (DFP). RESULTS: L70 showed a lower maximum σVM value (maxσVM), more uniform σVM distribution in the cortical bone, trabecular bone, and on the implant surface and a lower maximum DFp value (maxDFp), especially in the D4 bone. The biomechanical behaviors were similar in L45 and S45 with no stress distribution in the pterygoid process. In the D4 bone, L70, L45, and S45 exceeded the limited stress of the bone failure theory by 50%, 130%, and 130%, while all values were under the limit in D3 bone. CONCLUSIONS: The approach of pterygoid implants inclined at 70 degrees relative to the Frankfort plane with anchorage in the pterygoid process was optimal, providing improved biomechanical behavior. Clinically, in the case of D4 bone, the inclined angulation of pterygoid implants should be 70 degrees to minimize the risk of failure.

Effects of different distractor positions on the formation of expansion, stress and displacement patterns in surgically assisted rapid maxillary expansion without pterygomaxillary disjunction: a finite element analysis study.

Skeletal orthopedic expansion of maxilla is accepted as a reliable method for the treatment of transverse maxillar deficiency in growing patients. The aim of the study was to evaluate the effects of different palatal distractor positions on the expansion, stress and displacement patterns of the structures of craniofacial complex in surgical assisted rapid maxillary expansion without pterygomaxillary disjunction (PTMD) with the help of finite element analysis(FEA). Four facial skeleton models with different distractor positions (first premolar, second premolar, first molar, second molar regions) were created. In all finite element models median and lateral osteotomies were performed, without PTMD. Stress distribution was evaluated after 5 mm activation of the transpalatal distraction in all models using the nonlinear solution method in FEA. Unilateral displacement(mm) and stress distribution(MPa) were measured in three directions (x, y, and z axes) of craniofacial and maxillofacial structures in the symmetrical finite element models. In all models, the unilateral transverse displacements of the anterior teeth were greater than those of the posterior teeth, and the greatest displacement was at the central incisor level. The greatest displacement values at the central incisor level, at the anterior nasal spine(ANS) and at the posterior nasal spine(PNS) levels was measured in Model-IV, III, II and I, respectively. Mean elemental stress(von Mises stress) in the medial pterygoid plate, screw and lateral pterygoid plate regions from highest to lowest was measured in Model-IV, III, II and I, respectively. The maxilla performed outward rotation and tipping movement in all models during the expansion period. Among the distractor positions, the second molar region was found to be the most advantageous one in terms of expansion pattern. Considering the patient's anatomy and clinical conditions, placing the palatal distractor as posteriorly as possible will result in more effective maxillary expansion.

Modified orbitozygomatic craniotomy with a single burr hole in the alternative sphenoid ridge keyhole.

BACKGROUND: One-piece modified orbitozygomatic approach (OZA) is an extended version of the pterional approach that also includes orbital walls and frontal process of the zygomatic bone. For this craniotomy one burr hole must be placed in MacCarty keyhole and another - in the temporal region. OBJECTIVE: To develop a technique of the one-piece modified OZA with single a burr hole in the alternative sphenoid ridge keyhole that allows access to orbit, anterior cranial fossa and middle cranial fossa and apply it intraoperatively. METHODS: A single human head specimen was used. The dissection was performed using standard surgical instruments high-speed Stryker drill. Every stage of the approach was photographed. We also report a surgical case of a patient with orbital cavernous hemangioma that was resected using the described technique. RESULTS: The technique of the one-piece modified OZA with a single burr hole in the alternative sphenoid ridge keyhole is described, and its advantages and limitations are analyzed. The technique is used to totally resect an orbital cavernous hemangioma with good functional and cosmetic result. CONCLUSION: Modified OZA with a single burr hole in the sphenoid ridge keyhole is possible and may be an alternative to the classic technique. The advantages of this variation are the placement of just one burr hole and the preservation of a larger portion of the orbital roof. The latter facilitates better bone reconstruction and better cosmetic outcome. Disadvantages are the difficulty of identifying the location of the sphenoid ridge keyhole and risk of damaging the dura.

Volumetric Analysis of Spheno-Orbital Meningiomas: Prognostic Correlation and a Compartmentalized Approach.

BACKGROUND AND OBJECTIVES: Spheno-orbital meningiomas arise from the arachnoid villi cap cells at the sphenoid ridge and have the ability to spread through soft tissue extension and cranial bone invasion. Owing to their orbital hyperostosis and intraorbital soft tissue extension, they commonly present with ophthalmologic manifestations. This study aims to investigate the correlation between tumor volume with the presenting symptoms and postoperative outcomes. METHODS: This retrospective study analyzed patients who underwent surgical resection of spheno-orbital meningiomas. Tumor volumes in different compartments were measured using preoperative and postoperative imaging. Linear and logistic regression analyses were used to identify correlations between tumor volumes and presenting symptoms preoperatively and postoperative outcomes. RESULTS: Sixty-six patients were included in this study, of whom 86.4% had proptosis, 80.3% had decreased visual acuity (VA), 30.3% had visual field defects, and 13.6% had periorbital edema. Preoperatively, proptosis linearly correlated with intraosseous tumor volume (coefficient = 0.6, P < .001), while the decrease in baseline VA correlated with the intraorbital tumor volume (coefficient = 0.3, P = .01). The odds of periorbital edema were found to increase with an increase in intraosseous tumor volume with an adjusted odds ratio of 1.4 (95% CI, 1.1-1.7, P = .003), while the odds of visual field defects were found to increase with an increase in intraorbital tumor volume with an adjusted odds ratio of 2.7 (95% CI, 1.3-5.6, P = .01). Postoperatively, the volume of intraosseous tumor resected linearly correlated with the improvement in proptosis (coefficient = 0.7, P < .001), while the volume of intraorbital tumor resected linearly correlated with improvement in VA (coefficient = 0.5, P < .001) and with a larger effect size in patients presenting with moderate-to-severe decrease in VA preoperatively (coefficient = 0.8). CONCLUSION: Underscoring the importance of each tumor compartment relative to the patient's symptomatology serves as a valuable guide in implementing a compartmentalized resection approach tailored to the surgical objectives.

Optic Canal Size is an Indicator for the Accessory Optic Canal: Applications for Anterior Clinoidectomy.

BACKGROUND: The ophthalmic artery normally travels with the optic nerve through the optic canal. However, sometimes, the ophthalmic artery travels through a foramen within the optic strut named an accessory optic canal, double optic canal, or ophthalmic canal. This variant puts individuals at an increased risk for blindness or death during anterior clinoidectomy due to unforeseen hemorrhage of the ophthalmic artery or internal carotid artery when the optic strut is separated from the body of the sphenoid bone. Several features make the accessory optic canal difficult to recognize on imaging: its variant nature, small size, and ability to masquerade as a caroticoclinoid foramen or a pneumatized sphenoidal structure. Hence, improved methods of presurgical identification are warranted. The aim of this study was to assess the size and shape of the optic canal, with and without a concomitant accessory optic canal, to determine whether measurement of the optic canal may provide useful information regarding the presence of an accessory optic canal. METHODS: In 191 dry crania, optic canals with and without concomitant accessory optic canals were assessed for the following parameters: canal area, canal perimeter, circularity, solidity, the axes and aspect ratio of a best-fit ellipse, and roundness. RESULTS: Normal optic canals were found to have a larger area (P = 0.036), perimeter (P = 0.043), and minor axis of a best-fit ellipse (P = 0.031) than the optic canals that occurred alongside accessory optic canals. CONCLUSIONS: Asymmetry in optic canal size can help indicate the presence of a unilateral accessory optic canal before surgery.

How I do it? Endoscopic endonasal transpterygoid repair of sphenoid lateral recess cerebrospinal fluid leak after previous unsuccessful transcranial surgery.

BACKGROUND: Direct access to the sphenoid lateral recess offers the best chance of sealing spontaneous cerebrospinal fluid (CSF) rhinorrhea caused by lateral sphenoid encephaloceles of the Sternberg canal defect. METHOD: We present a case of spontaneous left-sided sphenoid lateral recess CSF leak after previous unsuccessful transcranial surgery managed with an endoscopic endonasal transpterygoid approach (EETA). An anatomical-based step-by-step illustration of the EETA was presented in the surgical video. CONCLUSION: This case demonstrates the value of endoscopic endonasal transpterygoid corridor in the exposure and manipulation of the sphenoid lateral recess.

How I do it: micro-neurosurgical resection of spheno-orbital meningioma with customized orbit reconstruction technique.

BACKGROUND: Spheno-orbital meningioma (SOM) is a rare intracranial pathology with intraosseous hypertrophy and intraorbital extension. METHOD: We described a middle-aged female with SOM who was managed in a micro-neurosurgical manner. The titanium implant was customized and applied to rebuild the orbital wall to prevent postoperative enophthalmus. CONCLUSION: Despite technical demands, favorable cosmetic, and clinical outcomes without complications can be achieved by meticulous surgical technique following radical resection. CLINICAL TRIAL REGISTRATION: NA.

Paraclinoid aneurysms clipping through an extradural sphenoid ridge keyhole approach.

BACKGROUND: Paraclinoid aneurysms represent a challenge for neurosurgeons due to the anatomical complexity of this region. Then, innovative techniques such as the extradural sphenoid ridge approach are suitable for a safe microsurgical clipping. METHOD: A description of the surgical technique was made by the senior author, a vascular neurosurgeon experienced with the use of this approach in the management of paraclinoid aneurysms exemplified through a clinical case. CONCLUSION: Microsurgical clipping through an extradural sphenoid ridge keyhole approach for small and midsize paraclinoid aneurysms is an excellent treatment modality with good clinical and surgical results.

A Six-Surface System to Describe Anatomy of Anterior Clinoid Process and Its Application in Anterior Clinoidectomy and Resection of Paraclinoid Meningioma.

OBJECTIVE: The anterior clinoid process (ACP) is surrounded by nerves and vessels that, together, constitute an intricate anatomical structure with variations that challenges the performance of individualized anterior clinoidectomy in treating lesions with different extents of invasion. In the present study, we established a 6-surface system for the ACP based on anatomical landmarks and analyzed its value in guiding ACP drilling and resection of paraclinoid meningiomas. METHODS: Using the anatomical characteristics of 10 dry skull specimens, we set 9 anatomical landmarks to delineate the ACP into 6 surfaces. Guided by our 6-surface system and eggshell technique, 5 colored silicone-injected anatomical specimens were dissected via a frontotemporal craniotomy to perform anterior clinoidectomy. Next, 3 typical cases of paraclinoid meningioma were selected to determine the value of using our 6-surface system in tumor resection. RESULTS: Nine points (A-H and T) were proposed to delineate the ACP surface into frontal, temporal, optic nerve, internal carotid artery, cranial nerve III, and optic strut surfaces according to the adjacent tissues. Either intradurally or extradurally, the frontal and temporal surfaces could be identified and drilled into depth, followed by skeletonization of the optic nerve, cranial nerve III, internal carotid artery, and optic strut surfaces. After the residual bone was removed, the ACP was drilled off. In surgery of paraclinoid meningiomas, our 6-surface system provided great benefit in locating the dura, nerves, and vessels, thus, increasing the safety of opening the optic canal and relaxing the oculomotor or optic nerves and allowing for individualized ACP drilling for meningioma removal. CONCLUSIONS: Our 6-surface system adds much anatomical information to the classic Dolenc triangle and can help neurosurgeons, especially junior ones, to increase their understanding of the paraclinoid spatial structure and accomplish individualized surgical procedures with high safety and minimal invasiveness.