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Objective: This article aims to discuss the surgical nuances and major adjustments necessary in unlocking the frontotemporal dural fold (FTDF) and extradural anterior clinoidectomy (EDAC) in actual cases, allowing translation from the cadaveric to a clinical scenario. Materials and Methods: We retrospectively reviewed the technical details of 17 procedures over 8 years, where both the initial steps (FTDF unlocking and EDAC) were performed. Lesions involving or extending to the anterolateral skull base, like the suprasellar cistern, optico-carotid cistern, interpeduncular cistern, petrous apex, and cavernous sinus, were included. The clinical data of the patients were retrieved retrospectively from the hospital information system (HIS) and in-patient records. This study was approved as a multicenter individual project with IEC No: 2020-342-IP-EXP-34. Results: An illustrated note of the common steps and outcome of the 17 procedures of unlocking the FTDF and EDAC done is presented. The technique provided adequate exposure in performing aneurysmal clipping (posterior communicating artery [P. com], basilar top, and superior hypophyseal artery [SHA] aneurysm), giant pituitary adenoma (Wilson Hardy grade 4E, n = 2), fifth nerve schwannoma (n = 4), right Meckel's cave melanoma, cavernous hemangioma (n = 4), petroclival meningioma (n = 2), and clival chordoma. Temporary and permanent cranial nerve palsy as a procedure-related complication was seen in 11.8% (n = 2) each. Complete excision was achieved in 13 (n = 13/14) patients with tumors. Conclusion: FTDF unlocking and EDAC are elegant procedures providing reasonable access to the anterolateral skull base for myriad pathologies. Brain bulge, cavernous sinus bleeding, and losing the plane of dural duplication were significant challenges in switching from cadaveric to a clinical scenario.

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BACKGROUND: Anterior clinoidectomy is an important procedure used in the treatment of a range of diseases of the frontotemporal region, both vascular and tumoral. Mastering this technique requires a high level of manual skills training. The objective of the study was to describe an easily accessible and economical alternative model of anterior clinoidectomy, with a principal focus on the significance of mastering technical skills and training tactile feedback. METHODS: Five cadaveric sheep heads (10 sides) fixed in formalin and alcohol were injected with silicone and used to simulate extradural (5 sides) and intradural (5 sides) routes and 1 head was used to prepare an anatomic specimen for better demonstration of the anatomy of the paraclinoid region. RESULTS: A comparative anatomic analysis between the ovine and human anterior clinoid process was performed. Using cadaveric sheep models, all principal steps of the procedure for both the extradural and the intradural routes were imitated. CONCLUSIONS: A cadaveric sheep head model serves as a good model of anterior clinoidectomy regarding manual skills training and can serve as a good alternative to human cadaveric training.

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Surgical treatment of functional pituitary adenomas is as rule performed by transsphenoidal approach. However, when then lesion invades the parasellar structures and the cavernous sinus, the transsphenoidal removal of these adenomas is usually incomplete. In this video, we present the technical nuances of a transcavernous approach to the anterio-medial triangle for the resection of a residual functional pituitary adenoma. The patient is a 40-year-old male who was diagnosed with growth hormone secreting pituitary macroadenoma. He underwent two transsphenoidal resections in 2013 and 2016 with a small residue in the left cavernous sinus. Subsequently, due to a failure of biochemical remission despite medical management, a transcranial transcavernous surgery was performed. Brain magnetic resonance imaging showed a mass in the roof of the left cavernous sinus, located at the level of the anteromedial triangle, adherent to the clinoidal segment of the internal carotid artery (ICA). The computed tomographic scan showed an osteolysis of the inferior surface of the anterior clinoidal process. After performing an extended pterional craniotomy and an extradural clinoidectomy, the cleavage plane is extended between the temporal dura and the inner layer of the lateral wall of the cavernous sinus. Intraoperative Doppler and stimulation are used to localize the clinoidal segment of the ICA and the third cranial nerve, delimiting the anteromedial triangle. The lesion is progressively dissected and removed. An optic neuropexy with the previously harvested fat is performed in case of a complementary radio surgical treatment. The patient had an uneventful postoperative course and showed a biochemical remission at the 3-month follow-up. The link to the video can be found at: https://youtu.be/oHfugVtU-Nc .

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Anterior clinoidal meningiomas (ACMs) remain a major neurosurgical challenge. The skull base techniques, including extradural clinoidectomy and optic unroofing performed at the early stage of surgery, provide advantages for improving the extent of resection, and thereby enhancing overall outcome, and particularly visual function. Additionally, when the anterior clinoidal meningiomas encase neurovascular structures, particularly the supraclinoid internal carotid artery and its branches, this further increases morbidity and decreases the extent of resection. Although it might be possible to remove the tumor from the artery wall despite complete encasement or narrowing, the decision of whether the tumor can be safely separated from the arterial wall ultimately must be made intraoperatively. The patient is a 75-year-old woman with right-sided progressive vision loss. In the neurological examination, she only had light perception in the right eye without any visual acuity or peripheral loss in the left eye. MRI showed a homogeneously enhancing right-sided anterior clinoidal mass with encasing and narrowing of the supraclinoid internal carotid artery (ICA). Computed tomography (CT) angiography showed a mild narrowing of the right supraclinoid ICA with associated a 360-degree encasement. The decision was made to proceed using a pterional approach with extradural anterior clinoidectomy and optic unroofing. The surgery and postoperative course were uneventful. MRI confirmed gross total resection ( Figs. 1 and 2 ). The histopathology was a meningothelial meningioma, World Health Organization (WHO) grade I. The patient continues to do well without any recurrence and has shown improved vision at 15-month follow-up. This video demonstrates important steps of the microsurgical skull base techniques for resection of these challenging tumors. The link to the video can be found at https://youtu.be/vt3o1c2o8Z0.

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Giant paraclinoid internal carotid artery (ICA) aneurysms are surgically challenging, mainly owing to lack of adequate working space and distortion of the regional anatomy. Anterior clinoidectomy is a vital surgical technique in such cases, allowing optic nerve decompression and exposure of the proximal ICA outside the confines of the arachnoid. While clinoidectomy is generally conducted intradurally, some aneurysms, particularly unruptured and directed medially paraclinoid ICA aneurysms, can allow a completely extradural clinoidectomy. Extradural clinoidectomy avoids bone dust spillage and drill bit-related injury from prolonged intradural drilling times. An 18-year-old man with a giant left superior hypophyseal artery aneurysm presented with progressive headache and visual diminution. He had a very good cross-flow from the contralateral ICA and tolerated balloon test occlusion. The aneurysm was exposed after extradural clinoidectomy and optic nerve mobilization. It was a wide-necked aneurysm and involved the distal dural ring. Owing to intraoperative somatosensory evoked potential findings as well as our concern of inadequate neck occlusion in view of the distal dural ring involvement and a possible future aneurysm regrowth, we trapped the aneurysm. The patient made an uneventful recovery with improvement in vision and normal visual fields. This video demonstrates the feasibility and utility of extradural clinoidectomy in adequate exposure of giant paraclinoid aneurysms and the role of aneurysm trapping for definitive aneurysm obliteration when the distal dural ring is involved. Trapping, in contrast to direct clipping, avoids manipulation of the compressed optic nerves, which is necessary for an optimal environment for postoperative visual recovery.

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BACKGROUND: Paraclinoid segment aneurysms arise from the internal carotid artery (ICA) between the distal dural ring and the origin of the posterior communicating (PComm) artery. OBJECTIVE: This pictorial study presents videos showing clipping of paraclinoid segment aneurysms. MATERIALS AND METHODS: The various subtypes of these aneurysms, the nuances in the technique of clinoidectomy, and methods of proximal control are presented. RESULTS: Cavernous ICA is designated as C4, clinoidal segment (between the proximal and distal dural rings) as C5, and supraclinoid segment (between the distal dural ring up to the PComm artery as C6 segment. The techniques used for clipping various aneurysms are based upon their subtypes and location. In the first case, in a giant superior hypophyseal artery aneurysm directed toward the suprasellar region, an intradural clinoidectomy helped in accessing the neck of the aneurysm encroaching into the clinoidal segment of ICA. In the second case, concurrent bilateral "kissing" paraclinoid segment aneurysms were clipped using a unilateral approach. In the third case, clipping of a dissecting paraclinoid segment aneurysm is demonstrated. CONCLUSIONS: Surgery still represents the most definitive form of treatment. It may also be used to evacuate an intracerebral hematoma, with an extremely tortuous proximal vessel or in an aneurysm with complex anatomy, with blister aneurysms, or following aneurysm regrowth following a failed endovascular procedure. Assessing the three-dimensional anatomy of various segments of ICA is an important step.

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BACKGROUND AND INTRODUCTION: Unlocking of the frontotemporal dural fold (FTDF) and extradural removal of the anterior clinoid process (EACP) are challenging but mandatory skills for micro-neurosurgeons. Despite the presence of an extensive body of literature on this subject, the translation of this cadaveric and 3D simulation to a real patient turns out to be a very demanding and difficult task. OBJECTIVE: This video is aimed to address the surgical nuances and major adjustments necessary in the unlocking of the FTDF and extradural ACP removal in an actual case for an early-career neurosurgeon. SURGICAL TECHNIQUE: A 40-year lady presented with features of acromegaly with radiological evidence of significant component of the tumor in the right cavernous sinus along with sellar suprasellar component. To achieve a good hormonal control, a complete tumor excision was required, which was achieved with FTDF and EACP removal. The cavernous sinus was approached through the Parkinson's triangle. RESULTS: The patient had uneventful recovery and good hormonal control at the 3-month follow-up. CONCLUSION: FTDF unlocking and EACP are elegant procedures and need to be learned by all neurosurgeons. This article will provide excellent teaching material for young neurosurgeons.

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Anterior clinoidectomy (AC) is a key microsurgical step for the safe and successful management of parasellar pathologies that involve the anterior clinoid process (ACP) and the optic canal. Traditionally, extra and intradural ACs are performed separately according to the surgeon's experience or preference. The objective is to present and discuss the tailored AC concept through illustrative cases. We conducted a retrospective record review of three patients who underwent AC as a surgical step for the treatment of parasellar pathologies that involve the ACP and optic canal. A review of the relevant literature on AC was performed in the PubMed, LILACS, and SciELO databases. In all three cases, the pterional craniotomy was the preferred approach for AC. Case 1, a 47-year-old female patient with type III anterior clinoidal meningioma, underwent a tailored intradural technique (optic canal unroofing) with total tumor resection and complete visual recovery. Case 2, a 63-year-old female patient with a complex type II anterior clinoidal meningioma with extensive hyperostosis of the ACP, underwent a hybrid AC technique with complete removal of the tumor and visual improvement. Case 3, a 62-year-old female, underwent a tailored intradural AC for clipping an incidental carotid-ophthalmic aneurysm. Tailored AC aims to provide adequate exposure with less risk of neurovascular injury, allowing enough space to safely treat parasellar lesions. The type, size, and location of the lesion, as well as the surgeon's experience, should always be considered for surgical planning.

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BACKGROUND: The endoscopic transorbital approach (eTOA) is a new mini-invasive procedure used to explore different areas of the skull base. Authors propose an extradural anterior clinoidectomy (AC) through this corridor, defining the anatomical landmarks of the anterior clinoid process (ACP) projection onto the posterior orbit wall and the technical feasibility of this approach. We describe the exposure of the opticocarotid region and the surgical freedom and the angles of attack obtained with this novel approach. METHODS: Five cadaver heads underwent an eTOA at the Laboratory of Surgical Neuroanatomy of the University of Barcelona. A step-by-step description of the extradural endoscopic transorbital clinoidectomy was provided. A volumetric analysis of the morphometrics characteristics of the sphenoid wings was evaluated before and after dissection using CT scans. Pterional approach was performed to ascertain ACP removal. RESULTS: In all the specimens, it was possible to resect the ACP endo-orbitally aiming an optimal optic canal (OC) unroofing. The surface of the triangle corresponding to the ACP projection onto the posterior orbit wall was 0.42 ± 0.20 cm2. The drilled area to perform the extradural clinoidectomy via eTOA was 3.11 ± 2.27 cm2, and the volume of bone removal corresponding to the greater sphenoid wing (GSW) and lesser sphenoid wing (LSW) was 2.55 ± 1.41 and 0.26 ± 0.18 cm3 respectively. The area of surgical freedom provided by the eTOA was (3.11 ± 2.27cm2), and the angles of attack were 21.39 ± 9.13° in the horizontal axel and 30.63 ± 18.51° in the vertical. CONCLUSIONS: The described extradural anterior clinoidectomy by eTOA uses specific landmarks to localize the ACP on the posterior orbit wall. Resection of the ACP is a technically feasible approach, achieving the main goals of any clinoidectomy.

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PURPOSE: The complex relations of the paraclinoid area make the surgical management of the pathology of this region a challenge. The anterior clinoid process (ACP) is an anatomical landmark that hinders the visualization and manipulation of the surrounding neurovascular structures, hence in certain surgical interventions might be necessary to remove it. We reviewed the anatomical relationships that involve the paraclinoid area and detailed the step-by-step techniques of intra and extradural clinoidectomy in cadaveric specimens. MATERIALS AND METHODS: A literature review was done describing the most relevant anatomic relationships regarding the anterior clinoid process. Extradural and intradural clinoidectomy techniques were performed in six dry bone heads and in ten previously injected cadaverous specimens with colored latex (Sanan et al. in Neurosurgery 45:1267-1274, 1999) and each step of the procedure was recorded using photographic material. Finally, an analysis of the anatomical exposure achieved in each of the techniques used was performed. RESULTS: The main advantage of the intradural clinoidectomy technique is the direct visualization of the neurovascular structures adjacent to the ACP when drilling, at the same time, opening the Sylvian fissure will allow the direct visualization of the ACP variants. The main advantage offered by the extradural technique is that the dura protects adjacent eloquent structures while drilling. Among the disadvantages, it is noted that the same dura that would protect the underlying structures also prevents the direct visualization of these neurovascular structures adjacent to the ACP. CONCLUSION: We reviewed the anatomy of the paraclinoid area and made a step-by-step description of the technique of the anterior clinoidectomy in its intra- and extradural variants in cadaveric preparations for a better understanding.

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Extradural anterior clinoidectomy is an important tool for neurovascular and skull base surgery. This technique is cardinal for expanding access to the proximal carotid artery, optic nerve, sella, and the central skull base. The goal of anterior clinoidectomy is to reveal the more proximal ophthalmic and clinoidal segments of the internal carotid artery (ICA) while skeletonizing the proximal optic nerve. This maneuver expands the opticocarotid and carotid-oculomotor windows and therefore the operative corridor to the interpeduncular cisterns; both the carotid artery and optic nerve are partially untethered or liberated and can be more safely mobilized.

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A "keyhole" approach to a deep-lying skull base lesion, as such a clinoid meningioma, can be a daunting challenge.1-3 The minimally invasive exposure must be precisely placed and adequately wide to accomplish the surgical goal. Surgical rehearsal in virtual reality (VR) can not only increase the confidence of the surgeon through practice on patient-specific anatomy,4 but it can also generate navigation-integrated templates to ensure precise placement and adequate bone openings. In this operative video, we demonstrate the use of an augmented reality (AR) template in a 69-yr-old woman with a growing clinoid meningioma. The 3-dimensional, VR rendering (SNAP VR360, Surgical Theater Inc, Cleveland, Ohio) of her right clinoid meningioma was used in surgical rehearsal for the mini-pterional approach with extradural clinoidectomy. The optimal opening was saved as a VR file and, at surgery, projected into the eye-piece of the navigation-tracked microscope (Synchronized AR v3.8.0, Surgical Theater Inc). In this manner, the surgical opening in the template was visible in AR on the patient's anatomy in real time during surgery. The template enhanced the planning of the incision and soft-tissue exposure, guided the drilling of the sphenoid wing, facilitated the extradural clinoidectomy,5 and ultimately facilitated the accomplishment of the surgical goal of total resection of the meningioma. With this application of novel technology, the surgeon is no longer using navigation to get her/his bearings. Instead, the surgeon is using AR-enhanced navigation to duplicate a plan that is known to work. This is a fundamental paradigm shift. Patient consent was obtained prior to the creation of the video and is available on request.

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Background We report a case of isolated metastasis on the anterior clinoid process (ACP) mimicking meningioma. Clinical Presentation A 58-year-old male presented with headaches, right-sided visual disturbances, and blurred and double vision. The cause of double vision was partial weakness of the right III nerve, resulting from compression of the nerve by "hypertrophied" tumor-involved right anterior clinoid. Medical history revealed two primary malignant tumors-male breast cancer and prostate cancer (diagnosed 6 and 18 months prior, respectively). The patient was treated with chemotherapy and showed no signs of active disease, recurrence, or metastasis. Postcontrast head magnetic resonance imaging (MRI) showed extra-axial well-bordered enhancing mass measuring 1.6 × 1.1 × 1 × 1 cm (anteroposterior, transverse, and craniocaudal dimensions) on the ACP, resembling a clinoidal meningioma. Extradural clinoidectomy with tumor resection was performed via right orbitozygomatic pretemporal skull base approach. Visual symptoms improved. Follow-up MRI showed no signs of tumor residual or recurrence. Conclusion This is the first case report of a metastasis of any kind on ACP. Metastasis should be included as a part of the differential diagnosis of lesions of the anterior clinoid. Extradural clinoidectomy is a safe and effective method in the treatment of these tumors.

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Se presenta la experiencia personal en el tratamiento de 5 pacientes con 7 aneurismas paraclinoideos tratados quirúrgicamente en el Hospital Regional Temuco durante junio de 2015 y julio de 2016 (13 meses). Todos los pacientes fueron previamente discutidos con neurorradiologo Intervencional local y considerados no favorables para terapia endovascular. En todos ellos se realizó una craneotomía mini pterional con clinoidectomía extradural y exposición de la arteria carótida interna cervical. Cuatro pacientes consultaron con hemorragia subaracnoidea y requirieron cirugía cerebral de urgencia. En 6 aneurismas se realizó clipaje y en 1 trapping. Cuatro pacientes no tuvieron deterioro neurológico y evolucionaron favorablemente mientras que 1 paciente falleció por hipoperfusión secundario al trapping de la carótida supraclinoidea. Se enfatiza el manejo interdisciplinario, el plan preoperatorio y el conocimiento de la neuroanatomía en el tratamiento de esta patología.

A personal experience is presented in treating 5 patients with 7 paraclinoid aneurysm who underwent surgery at Hospital Regional Temuco between june 2015 and july 2016 (13 months). All patients were previously discussed with local interventional neuroradiologist considering them not favorable to endovascular therapy. Mini pterional craniotomy with extradural clinoidectomy and internal cervical carotid artery exposure was performed in all of them. 4 patients presented with subarachnoid hemorrhage and required urgent brain surgery. Direct clipping was optimal in 6 aneurysm and 1 was treated with trapping. 4 patients had no neurological deteriotation with excellent outcome and 1 patient died because of hypoperfusion secondary to the supraclinoid carotid trapping. Interdisciplinary management, preoperative planning and neuroanatomy knowledge are emphasized in order to treat this pathology.

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BACKGROUND: Extradural removal of the anterior clinoid process (ACP) is a crucial step in the proper surgical exposure of various pathologies in and around the central skull base. Since the pioneering description by Dolenc, the technique of extradural clinoidectomy has undergone several refinements in the light of improved understanding of microsurgical anatomy and maturation of neurosurgical techniques. Mastery of the surgical nuances involved in performing this surgical exercise will allow the young neurosurgeon to execute this step without undue reluctance and trepidation. OBJECTIVE: This paper is an attempt to describe in detail, from a learner's viewpoint, the sequence of maneuvers involved in extradural removal of the ACP. MATERIALS AND METHODS: The standard pterional approach and extradural anterior clinoidectomy was performed on four sides of two formalin fixed and latex injected cadaver heads. Important steps were photographed through the surgical microscope. CONCLUSION: An accurate understanding of the microsurgical anatomy of this region and the surgical nuances relevant to extradural clinoidectomy helps simplify the complexity of this surgical step.

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OBJECTIVE: Removal of the anterior clinoid process (ACP) is an essential process in the surgery of giant or complex aneurysms located near the proximal internal carotid artery or the distal basilar artery. An extradural clinoidectomy must be performed within the limits of the meningeal layers surrounding the ACP to prevent morbid complications. To identify the safest method of extradural exposure of the ACP, anatomical studies were done on cadaver heads. METHODS: Anatomical dissections for extradural exposure of the ACP were performed on both sides of seven cadavers. Before dividing the frontotemporal dural fold (FTDF), we measured its length from the superomedial apex attached to the periorbita to the posterolateral apex which connects to the anterosuperior end of the cavernous sinus. RESULTS: The average length of the FTDF on cadaver dissections was 7 mm on the right side and 7.14 mm on the left side. Cranial nerves were usually exposed when cutting FTDF more than 7 mm of the FTDF. CONCLUSION: The most delicate area in an extradural anterior clinoidectomy is the junction of the FTDF and the anterior triangular apex of the cavernous sinus. The FTDF must be cut from the anterior side of the triangle at the periorbital side rather than from the dural side. The length of the FTDF incision must not exceed 7 mm to avoid cranial nerve injury.

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OBJECTIVE: Removal of the anterior clinoid process (ACP) is an essential process in the surgery of giant or complex aneurysms located near the proximal internal carotid artery or the distal basilar artery. An extradural clinoidectomy must be performed within the limits of the meningeal layers surrounding the ACP to prevent morbid complications. To identify the safest method of extradural exposure of the ACP, anatomical studies were done on cadaver heads. METHODS: Anatomical dissections for extradural exposure of the ACP were performed on both sides of seven cadavers. Before dividing the frontotemporal dural fold (FTDF), we measured its length from the superomedial apex attached to the periorbita to the posterolateral apex which connects to the anterosuperior end of the cavernous sinus. RESULTS: The average length of the FTDF on cadaver dissections was 7 mm on the right side and 7.14 mm on the left side. Cranial nerves were usually exposed when cutting FTDF more than 7 mm of the FTDF. CONCLUSION: The most delicate area in an extradural anterior clinoidectomy is the junction of the FTDF and the anterior triangular apex of the cavernous sinus. The FTDF must be cut from the anterior side of the triangle at the periorbital side rather than from the dural side. The length of the FTDF incision must not exceed 7 mm to avoid cranial nerve injury.

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