Anterior Clinoid Process Research Articles

A Comprehensive Computed Tomographic Analysis of Pneumatization Pattern of Sphenoid Sinus and Their Association with Protrusion/Dehiscence of Vital Neurovascular Structure in a Pakistani Subgroup.

To determine the clinically significant association between pneumatization types of the sphenoid sinus (SS) and protrusion/ dehiscence of the optic nerve (ON) and the internal carotid artery (ICA). This prospective cross-sectional study was conducted between November 2020 and April 2021 at the Dow Institute of Radiology, Dow University of Health Sciences, Karachi. This study examined 300 computed tomography (CT) PNS patients aged 18-60 years. The forms of SS pneumatization, extent of pneumatization to the greater wing (GW), anterior clinoid process (ACP), and pterygoid process (PP), as well as the protrusion/dehiscence of the ON and ICA were examined. A statistical relationship was identified between pneumatization type and protrusion/dehiscence of the ON and ICA. The study included 171 men and 129 women with an average age of 39.28 ± 10.9 years. The most commonly encountered pneumatization type was postsellar (63.3%), followed by sellar (27.3%), presellar (8.7%), and conchal (0.75%). The most frequent extended pneumatization was observed up to PP (44%), followed by ACP (31.33%), and GW (16.67%). The rate of dehiscence of the ON and ICA was less than that of protrusion of the same structures. The association between postsellar and sellar pneumatization types and protrusion of the ON and ICA was statistically significant (p < 0.001), with the postsellar type showing more protrusions of the ON and ICA than the sellar type. The pneumatization type of SS has a significant impact on the protrusion/dehiscence of adjacent vital neurovascular structures and should be mentioned in CT reports to alert surgeons for any disastrous intraoperative complications and outcomes.

Incidence of Ossification of Caroticoclinoid Ligament in Dry Adult Human Skulls with its Surgical Implications: A Cross-sectional Study from Telangana Region, India

Introduction: The caroticoclinoid ligament extends from the Anterior Clinoid Process (ACP) to the Middle Clinoid Process (MCP). Occasionally, it gets ossified and forms the caroticoclinoid foramen. Anterior clinoidectomy is a common surgical procedure to treat internal carotid artery aneurysms or pituitary tumours. Abnormal ossification of the caroticoclinoid ligament may lead to intraoperative or postoperative complications as it is not normally present. Aim: To find out the incidence of ossification of the caroticoclinoid ligament in adult human skulls. Materials and Methods: This was an observational crosssectional study that included 100 dry adult human skulls collected from the Department of Anatomy, Gandhi Medical College, Secunderabad; Osmania Medical College, Hyderabad; Bhaskar Medical College, Moinabad, Telangana, India, from January 2021 to February 2023. Adult human skulls with open vault were included. All the skulls were observed and skulls damaged in the clinoid regions were excluded from the study. The skulls were observed for the presence of any ossifications of the caroticoclinoid ligaments and the observations were noted. The qualitative data was presented as number and percentage was calculated. The data was recorded in MS excel version 2021. Results: The incidence of ossification of caroticoclinoid ligament was 8 (8%). The incidence was higher on right-side when compared to the left-side. Bilateral complete ossification of the caroticoclinoid ligament was observed in 2 (2%) skulls; bilateral incomplete ossification was observed in 3 (3%) skulls, unilateral complete ossification was observed in 2 (2%) skulls on the right-side. In one skull 1 (1%), complete ossification was observed on the right-side and incomplete ossification was observed on the left-side. Conclusion: Knowledge of the ossification of the caroticoclinoid ligament is important for neurosurgeons while performing anterior clinoidectomies or skull base surgeries. Radiological confirmation of the ossification of the caroticoclinoid ligament is essential to avoid complications.

Evaluation of Anterior and Posterior Clinoid Process Pneumatization with Sphenoid Sinus Types

Evaluation of Anterior and Posterior Clinoid Process Pneumatization with Sphenoid Sinus Types

Extensive and Advanced Craniofacial Dysplasia

A 35-year-old Syrian patient presented to our department complaining of 7-year history of asymptomatic hard swelling in right side of the frontotemporal and naso-orbito-ethmoidal region, reaching the contralateral side (Panels A and B). Patient stated that from 1 year back his visual acuity has been decreased compared with the previous 6 years. Computed tomography (CT) with contrast (Panels C–F) showed diffuse bony expansion involving the frontal bones bilaterally. Bone expansion was more on the right side extending into the vertical plates as well as the horizontal plates forming the roof extending to involve the cribriform plates and into the crista galli extending posteriorly to involve the sphenoid bone including the body, greater and lesser wings of the sphenoid bone as well as the clinoid processes ends extending to the roots of the pterygoid plates. Multidisciplinary decision team meeting was done, with neurosurgery, anesthesiology, and maxillofacial surgery to decide the treatment. Under the general anesthesia the patient underwent remodeling and recontouring of the facial and cranial bones through bilateral occipital approach. Using the unilateral fronto-temporal extradural approach and retracting the dura and reaching the base of the skull the anterior clinoidectomy for optic nerve decompression was performed. Right clinoid process surgery reshaped the base of the skull releasing the bone which compressed the right orbital nerve. Affected bone which involved the frontotemporal area was removed and reconstruction was performed with cranioplasty fixed with osteosynthesis to the adjacent and healthy bony structures. The resected bone was submitted to Hamad general hospital histopathology laboratory which reported following fixation and decalcification irregular shaped trabeculae of immature woven bone scattered in a loosely hypercellular stroma histopathological diagnosed as fibrous dysplasia (Panels G and H: H&amp;E staining). After 5 days of medical management as inpatient, the patient was discharge with close follow up. Patient was followed up in a weekly basis with a normal postoperative status. 5 months after the surgery (Panel I, photography on postoperative day 120 showed remanent dystopia but generalized acceptable craniofacial projection), patient stated to have improvement in his visual acuity compared to his base line as well as craniofacial projection with a remanent vertical dystopia. Panels J and K compare preoperative CT (Panel J) where anterior clinoid process involved with the pathology is noted and postoperative CT (Panel K) which reveals removal of anterior clinoid process for orbital nerve decompression.

Morphometric analysis of oculomotor triangle in dry human skulls and its clinical applications.

The oculomotor triangle is denoted as the "Triangle of Hakuba" or the "Hakuba's Triangle." This oculomotor triangle is a significant anatomical landmark. Oculomotor nerve, abducens nerve and part of the internal carotid artery (ICA) lie in this triangle. The determination of this analysis is to calculate the oculomotor triangle in dry processed skull bones of the south Indian population and its clinical significance. Fifty-one processed skulls of human origin were received from Anatomy Department, Basic Medical Sciences, Saveetha Dental College. Length from anterior-clinoid process (ACP) to posterior-clinoid process (PCP), length from PCP to APEX, and length from ACP to APEX were measured. Paired samples t-test was considered to analyze the values between the right triangle with the left triangle. From the measurements taken, the mean for the left side of the oculomotor triangle, ACP to PCP was 8.0591 ± 0.52 mm and the right side was 7.5482 ± 0.52 mm. The mean left side of the oculomotor triangle, measured from PCP to APEX was 6.73 ± 0.48 mm and the right side was 6.55 ± 0.72 mm. The mean of the left side of the oculomotor triangle, measured from ACP to APEX was 15.94 ± 0.682 mm and the right side was 16.21 ± 0.747 mm. Through this paired triangle of the cranial cavity, the horizontal section of ICA may be correlated with numerous vascular-related pathological considerations.

Racial, Ethnic, and Gender Variations in Sinonasal Anatomy.

Complications during endoscopic sinus surgery often result from unfavorable anatomy. The prevalence rates of such anatomic findings vary tremendously in the literature, in part due to the small, homogenous populations previously studied. To characterize the prevalence of sinonasal anatomic variants among ethnic groups and genders seen at an academic medical center. This is a retrospective cross-sectional study of adult subjects who underwent CT imaging of the sinuses from January 2019 to November 2020 at a tertiary academic setting. CT scans were analyzed systematically by 3 trained study personnel for the presence of critical sinus anatomic variants that endoscopic sinus surgeons typically evaluate for preoperatively. Chi-squared tests and analyses of variance were conducted to detect differences in the prevalence of structural findings between genders and races/ethnicities. A total of 489 subjects (57% female) were included: 44 Asian, 14 Black/African American, 101 Hispanic/Latino, 203 White, 127 Other. The prevalence of the following anatomical variants differed by race/ethnicity: Haller cells, Type 3 optic nerve, Onodi cells, maxillary septations, sphenoid lateral recess, anterior clinoid process pneumatization, and carotid artery dehiscence. Asian subjects had higher rates of Haller cells (48% vs 16%, P < .001) and Type 3 optic nerve (18% vs 4%, P = .022) compared to Hispanic subjects, as well as a higher prevalence of Onodi cells (39% vs 17%, P = .003) compared to White subjects. Males had a higher prevalence of mesenteric anterior ethmoid arteries (62% vs 45%, P < .001) and dehiscent carotid arteries (30% vs 21%, P = .024). Certain sinonasal anatomic variants, which have direct implications for complications during endoscopic sinus surgery, were found to be significantly more prevalent in some demographic groups. Surgeons should be aware of these differences in their review of preoperative imaging for safe surgical planning.

Endoscopic Endonasal Anterior Clinoidectomy: Volumetric Assessment and Feasibility

Transcranial removal of the anterior clinoid process (ACP) provides access to the clinoidal segment of the internal carotid artery (ICA) as well as superolateral decompression of the optic canal. Endoscopic endonasal approaches (EEAs) can access the entire medial and inferior portions of the optic canal, but no data exists to support what proportion of the anterior clinoid which could be safely resected via an EEA. A cadaveric anatomical study was performed with removal of the ACP in 3 major steps in order of difficulty and risk. At each step, the removal was stopped when no more bone of the ACP could be seen without traction on neural structures. After each step, a CT scan was performed to allow volumetric measurement of the remaining ACP. Twenty ACP in 10 cadaveric heads were removed to various degrees using the described stepwise technique. The mean portion of the ACP resected by each step was 21%, 46% and 27%, respectively. Cumulated ACP removal at the end of step 3 was 94%, with complete removal achieved in 35% of the specimens. Using the safe route above the optic canal, removal of 21% of the ACP can be achieved via EEA. Although substantially more of the ACP can be drilled by accessing the optic strut, the benefits of pursuing additional removal must be weighed against the significant risks of drilling in this narrow corridor bordered by the ICA, the third cranial nerve and the optic nerve.

Septoplasti ve Septorinoplasti Hastalarında Etmoid Çatı Derinliğinin ve Sinonazal Anatomik Varyasyonların Retrospektif Radyolojik Analizi

Aim: Computed tomography (CT) provides an accurate assessment of sinonasal anatomy and osseocartilaginous pathologies in patients complaining of sinonasal symptoms. Although it is not a routine practice, CT is frequently used in preoperative screening of patients planned for septoplasty and septorhinoplasty. In this study, anatomical variations and ethmoid lateral lamella depths in preoperative CT images of septoplasty and septorhinoplasty operations performed in our clinic were analyzed retrospectively and discussed with current literature.&#x0D; Material and Method: Septorhinoplasty and septoplasty surgeries performed in our clinic between January 2014 and August 2018 over the age of 18 years were reviewed retrospectively. Two hundred patients were included in the study. CT images were evaluated for anatomical variations and ethmoid lateral lamella depths.&#x0D; Results: Of the 200 patients included in the study, 158 (79%) underwent septoplasty and 42 (21%) underwent septorhinoplasty. Concha bullosa was detected in 95 (47,5%) of the patients and was determined as the most common anatomical variation. Onodi cell variation was detected in 62 (31%) of the patients. Haller cell was detected in 37 patients (18,5%). Paradoxical middle turbinate was detected in 19 patients (9,5%), pneumatized anterior clinoid process in 17 patients (8,5%), and pneumatized crista galli in 4 patients (2%). In lateral lamella measurements; the median value of the lateral lamella depth on the right was 4,20 mm (0,40-7,40 mm) and the median value of the lateral lamella depth on the left was 4,20 mm (1,70-7,30 mm).&#x0D; Conclusion: Anatomical variations that can be detected in CT imaging before septoplasty and septorhinoplasty operations and information about ethmoid roof anatomy will be useful in case management, surgical planning and complication management.

Extradural Clinoidectomy in Clinoidal Meningiomas: Analysis of the Surgical Technique and Evaluation of the Clinical Outcome.

The surgical treatment of clinoidal meningiomas is currently still discussed in the literature. Different surgical approaches have been proposed and evaluated, in multiple studies, in order to improve the surgical outcomes. The aim of this study is to evaluate the advantages of extradural clinoidectomy in the context of tumor removal radicality for visual function improvement. A retrospective analysis was performed on 74 patients—of which 26 patients with clinoidal meningiomas were in group III, according to Al Mefty classification—who underwent surgery at the Policlinico Umberto I Hospital between 2000 and 2019. Further, extradural clinoidectomy was performed on 15 patients (Group A), and 11 patients underwent the pterional approach only (Group B). Additionally, visual impairment was present in all 26 patients before surgery. Next, visual function assessment was performed on all patients, both in presurgery and postsurgery. Radiological follow up was performed at 3 and 6 months, and then every 12 months. Gross Total Resection (GTR) was achieved in 13/15 (86.7%) patients who underwent clinoidectomy, and in 4/11 (36.4%) patients who did not undergo clinoidectomy. Visual function improvement was achieved in 12/15 (80%) patients who underwent clinoidectomy and in 4 of 11 (36.4%) who did not undergo clinoidectomy. According to our study, extradural clinoidectomy is the most suitable method for facilitating the gross total resection of clinoidal meningiomas. Our experience and data suggest that a higher rate of total resection and, subsequently, the best visual outcomes are achieved. Extradural drilling via the anterior clinoid process reveals a wider surgical corridor for meticulous tumor resection.

Morphometric measurements of anterior clinoid process in relation to parasellar osseous structures and their clinical significance

This study is to analyze the morphometry of anterior clinoid process (ACP) and the surrounding parasellar structures which is important for the surgeries related to cavernous sinus, ICA, and basilar artery. A cross-sectional study has been done on 77 adult human dry skulls among North Indian population. The length, width, thickness of ACP and distance between ACP to OS, distance between two ACPs, distance between PCPs, distance between ACP to PCP were measured using digital vernier caliper. The mean and standard deviation was calculated and paired t-test was applied for the comparison. The mean length and width and thickness of ACP was 8.72±0.94 mm, 8.13±1.16 mm and 1.10±0.44 mm on right and 8.57±0.91mm, 8.05±1.24 mm and 1.40±0.41mm on left side. The average distance between the ACP tip to OS and ACP and PCP tip was 6.01±1.11mm and 8.79±1.49mm on the right and 5.90±0.99mm and 8.47±1.49mm left side. The mean distance between the ACP tip and PCP tip was 20.10±2.36 mm and 12.63±2.03 mm respectively. We did not find any significant difference of morphometric parameters between the right and the left side. The anatomical knowledge of these structures and its variation will help surgeons to plan surgery around the parasellar region.

Partial medial clinoidectomy with optic canal roof drilling for clipping of ophthalmic artery aneurysms: how I do it.

Clipping of ophthalmic artery (OA) aneurysms present one of the treatment strategies for long-term disease management. Existing surgical techniques primarily require extra/intradural removal of the anterior clinoid process, carrying a higher risk of infection, damage to surrounding structures or technical complications. We present the technique of minimally invasive partial medial clinoidectomy with the unroofing of the optic canal for surgical clipping of OA aneurysms, and besides its pros and cons, we also discuss proper technical indications. The partial medial clinoidectomy improves manoeuvrability around the paraclinoid region, provides better protection for adjacent structures and renders excellent treatment outcome.

Endoscopic transorbital extradural anterior clinoidectomy: A stepwise surgical technique and case series study [SevEN-013

BackgroundAnterior clinoidectomy is an important procedure for approaching the central skull base lesions. However, anterior clinoidectomy through the endoscopic transorbital approach (ETOA) still has limitations due to technical difficulties and the structural complexity of the anterior clinoid process (ACP). Therefore, the authors designed a stepwise surgical technique of extradural anterior clinoidectomy through the ETOA. The purpose of this study was to evaluate the feasibility of this technique.MethodsAnatomical dissections were performed in 6 cadaveric specimens using a neuroendoscope and neuro-navigation system. The extradural anterior clinoidectomy through the ETOA was performed stepwise, and based on the results, this surgical technique was performed in the 7 clinical cases to evaluate its safety and efficiency.ResultsEndoscopic extradural anterior clinoidectomy was successfully performed in all cadaveric specimens and patients using the proposed technique. This 5-step technique enabled detachment of the lesser wing of sphenoid bone from the ACP, safe unroofing of the optic canal, and resection of the optic strut without injuring the optic nerve and internal carotid artery. Since the sequential resection of the 3 supporting roots of the ACP was accomplished safely, anterior clinoidectomy was then successfully performed in all clinical cases. Furthermore, no complications related to the anterior clinoidectomy occurred in any clinical case.ConclusionWe designed a stepwise surgical technique that allows safe and efficient anterior clinoidectomy through the ETOA. Using this technique, extradural anterior clinoidectomy can be accomplished under direct endoscopic visualization with low morbidity. Since this technique is applicable to the central skull base surgery where anterior clinoidectomy is necessary, it expands the application of the ETOA.

Change in the Location of the Optic Strut Relative to the Anterior Clinoid Process Pneumatization.

This study aimed to peruse the alteration of the position of the optic strut (OS) according to the anterior clinoid process (ACP) pneumatization. This retrospective study conducted on cone-beam computed tomography images of 400 patients with a mean age of 36.49±15.91 years. Anterior clinoid process length, width, and angle were measured as 10.56±2.42mm, 5.46±1.31mm, and 42.56±14.68 degrees, respectively. The tip of ACP was measured as 6.60±1.50mm away from the posterior rim of OS. In the 631 sides (78.87%) did not have ACP pneumatization. In the cases with ACP pneumatization, three different configurations were identified as follows: Type 1 in 71 sides (8.87%), Type 2 in 56 sides (7%), and Type 3 in 42 sides (5.23%). Relative to ACP, the location of OS was determined as follows: Type A in 29 sides (3.64%), Type B in 105 sides (13.12%), Type C in 344 sides (43%), Type D in 289 sides (36.12%), and Type E in 33 sides (4.12%). The spread of data related to the attachment site of OS according to the presence or absence of ACP pneumatization showed that the location of OS was affected by ACP pneumatization ( P <0.001). In ACPs with pneumatization, the frequency of OS position relative to ACP was found as follows: Type A in none of sides (0%), Type B in 8 sides (7.6%), Type C in 53 sides (15.4%), Type D in 88 sides (30.4%), and Type E in 20 sides (60.6%). The main finding of this study was that the location of OS relative to ACP was affected by ACP pneumatization. In ACPs with pneumatization, OS was located more posteriorly compared with ACPs without pneumatization.

Morphological types and localization patterns of pterion in the skulls of adults from southeastern China.

To study the morphological types and relative location of the pterion and its precise relationship with the middle meningeal artery (MMA) in the skulls of adults from southeastern China. Dry skulls (n = 250) of adults were obtained from a university specimen bank and analyzed. The morphological types of the pterions were observed. The distances from the center of the external pterion (Pec) to the relevant intracranial and extracranial marker points were measured using a digital vernier caliper. The anterior, middle, and posterior end points of the external pterion were drilled perpendicular to the bone surface. The precise relationships of the external pterion with the internal pterion and the groove of the frontal branch of the MMA were observed and measured after sawing the skull. The morphological types of the pterion in the skulls of adults from southeastern China were sphenoparietal suture (SP) (85%), epipteric (12.4%), frontotemporal suture (1.4%), and stellate (1.2%) types. The mean widths of the external and internal pterions were R, 10.68 ± 4.22mm; L, 11.13 ± 4.40mm and R, 14.66 ± 4.04mm; L, 14.14 ± 4.29mm, respectively, and the width of the internal pterion was slightly longer than that of the external (P < 0.05). No significant difference in pterion width was found between the genders or sides of the skull (both P > 0.05). The distances from the Pec to the posterolateral aspect of the frontozygomatic suture, zygomatic process of the frontal bone, midpoint of the zygomatic arch, and external acoustic meatus were 29.95 ± 3.75mm, 34.88 ± 4.08mm, 40.86 ± 3.59mm, and 53.79 ± 3.82mm, respectively. These distances were slightly longer on the right side of the skull than on the left side (P < 0.01) and longer in men than in women (P < 0.01). The distances from the Pec to the frontal crest, optic canal, and anterior clinoid process were 62.79 ± 1.15mm, 45.39 ± 2.48mm, and 45.47 ± 2.05mm, respectively. The external and internal pterions were not on the same level, and all the internal pterions were located below the external ones. In the vast majority of the skulls, the groove of the frontal branch of the MMA passed through the posterior end of the external pterion (Pep) or the area between the Pec and Pep. The morphology of the pterion in the skulls of adults from southeastern China is predominantly of the SP type, mostly symmetrically distributed. The distance from the pterion to the extracranially relevant marker points differs among the ethnic groups, between the genders, and between the sides of the skull. All the internal pterions are located below the external ones. Most of the frontal branch of the MMA is located below the mid-posterior segment of the lateral pterion. The characterization of the morphology, the relative position of the pterion and the precise relationship of this structure with the MMA in the skulls of adults from southeastern China may provide an anatomical basis for teaching and clinical practices.

Endoscopic Endonasal Supraoptic and Infraoptic Approaches for Complex "Parasuprasellar" Lesions: Surgical Anatomy, Technique Nuances, and Case Series.

ObjectiveThe surgical management of lesions involving the lateral area of the suprasellar region, including the lateral aspect of the planum sphenoidale and the tight junction region of the optic canal (OC), anterior clinoid process (ACP), and internal carotid artery (ICA) and its dural rings, is extremely challenging. Here, these regions, namely, the “parasuprasellar” area, are described from the endonasal perspective. Moreover, the authors introduce two novels endoscopic endonasal supraoptic (EESO) and endoscopic endonasal infraoptic (EEIO) approaches to access the parasuprasellar area.MethodsSurgical simulation of the EESO and EEIO approaches to the parasuprasellar area was conducted in 5 silicon-injected specimens. The same techniques were applied in 12 patients with lesions involving the parasuprasellar area.ResultsThe EESO approach provided excellent surgical access to the lateral region of the planum sphenoidale, which corresponds to the orbital gyrus of the frontal lobe. With stepwise bone (OC, optic strut and ACP) removal, dissociation of the ophthalmic artery (OA) and optic nerve (ON), the EEIO approach enables access to the lateral region of the supraclinoidal ICA. These approaches can be used independently or in combination, but are more often employed as a complement to the endoscopic endonasal midline and transcavernous approaches. In clinical application, the EESO and EEIO approaches were successfully performed in 12 patients harboring tumors as well as multiple aneurysms involving the parasuprasellar area. Gross total and subtotal tumor resection were achieved in 9 patients and 1 patient, respectively. For two patients with multiple aneurysms, the lesions were clipped selectively according to location and size. Visual acuity improved in 7 patients, remained stable in 4, and deteriorated in only 1. No postoperative intracranial infection or ICA injury occurred in this series.ConclusionsThe EESO and EEIO approaches offer original treatment options for well-selected lesions involving the parasuprasellar area. They can be combined with the endoscopic endonasal midline and transcavernous approaches to remove extensive pathologies involving the intrasellar, suprasellar, sphenoid, and cavernous sinuses and even the bifurcation of the ICA. This work for the first time pushes the boundary of the endoscopic endonasal approach lateral to the supraclinoidal ICA and ON.

Frontal sinus pneumatization: An isolated finding or a sign of concomitant anatomical variation?

To determine the association between frontal sinus pneumatisation and concomitant anatomical variations in paranasal sinuses as seen on computed tomography. A total of 403 patients who underwent paranasal sinus computed tomography were allocated to three groups according to the degree of frontal sinus pneumatisation (type 1 - hypoplasia; type 2 - medium size; and type 3 - hyperplasia). In this unique model, the prevalence of ipsilateral variations on paranasal sinuses on each side of the head were analysed separately within each pneumatisation group. The type 3 frontal sinus pneumatisation group showed a greater association with ipsilateral variations of the sphenoid bone. Variations included pneumatisation of the anterior clinoid process, lateral sphenoid recess, pterygoid process and greater wing, and exposure of Vidian canal. This group also showed significant associations with male gender, and the presence of frontal and Onodi cells. Interpretation of the paranasal sinus variations is imperative for pre-operative evaluation in functional endoscopic sinus surgery, particularly in patients with frontal sinus hyperplasia. Attention to variation on the ipsilateral side is informative.

Dolenc's Approach:Anterior Clinoidectomy and Extradural Approach to Cavernous Sinus

The combined epidural and subdural approach pioneered by Dolenc allows opening of the lateral wall of the cavernous sinus(CS)to treat various pathologies such as tumors and aneurysms in the cavernous, para-cavernous, and central skull base regions. The Dolenc's approach is occasionally performed with the orbitozygomatic approach(OZA), which enables us to look up highly located lesions. We prefer the two-piece method when performing OZA: it involves removing the orbitozygomatic bar separately after frontotemporal craniotomy. Dolenc's approach requires dividing the meningo-orbital band and opening the superior orbital fissure to expose the junction between the dura propria of the temporal lobe and inner membrane of the CS, which separates the neurovascular structures and the venous plexus inside. Peeling of the dura propria from the inner membrane is continued until the anterior clinoid process is exposed epidurally. Extradural clinoidectomy and optic canal opening are then performed. After the epidural procedures, intradural procedures are also performed. The falciform ligament and the distal dural ring are incised to mobilize the optic nerve and the internal carotid artery. The tentorium is incised along the anterior petroclinoid ligament. Dolenc's approach allows extradural retraction of the temporal lobe, which provides a surgical corridor to the retro-carotid space and the inter-peduncular cistern through the opened anterior part of the CS.

Modified intradural anterior clinoidectomy to protect the paraclinoid neurovascular structures: A technical note

ObjectiveAnterior clinoidectomy is effective in creating an adequate working field during surgery for paraclinoid lesions. However, intradural anterior clinoidectomy (iAC) is associated with intraoperative injury to the paraclinoid neurovasular structures because they are exposed in the surgical field. Here we introduce our modified technique in removing the anterior clinoid process (ACP) to compensate the drawbacks of iAC. MethodsThis technical case report is presented by demonstration of cadaver dissection and surgical video. ResultsCadaver dissection study demonstrates the step-by-step procedure. Our technique primarily aims at sectioning of the dura adjacent to the ACP to obtain both intradural and extradural operative fields. With this technique, the ACP can be safely removed without injuring the neurovascular structure, such as the optic nerve and internal carotid artery. As an example of its clinical application, we present a case of a 67-year-old woman with anterior clinoid meningioma and visual deficits. The ACP was safely removed using a high-speed drill without injuring the neurovascular structures. Gross total resection was achieved. Her vision returned to normal postoperatively. ConclusionsUsing our modified technique, the widely reflected dura covers the critical neurovascular structure during the skull base drilling. Therefore, this technique compensates the drawbacks inherent to iAC.

How I do it: management of M2 tear injury caused by drilling during intradural anterior clinoidectomy for microsurgical clipping of intracranial aneurysms.

High-speed drilling is associated with potential injury to neurovascular structures, particularly during intradural drilling of the anterior clinoid process. During an anterior clinoidectomy, a cotton patty and middle cerebral artery branches became inadvertently wrapped around the bit, causing a tear on the inferior M2 trunk. Following temporary clipping of the internal carotid artery, the tear was identified. Temporary clips were placed proximally and distally. The tear was then repaired with interrupted microsutures. Extreme care should be exercised during clinoidectomy. Should small vascular injury occur, direct microsuturing can be a good alternative to sacrificing or implantation anastomosis repair.

Posterior Clinoid Meningioma-A Formidable Entity: 2-Dimensional Operative Video.

Meningiomas originating from the posterior clinoid process are the rarest form of meningioma making up less than 1% of skull base meningiomas.1 These tumors have notoriously poor outcomes characterized by incomplete resections and a litany of complications.1 Owing to their scarcity and frequent confusion with meningiomas arising from adjacent skull base regions, the surgical anatomy, technical nuances, and potential pitfalls are not well addressed in modern literature. The most challenging aspect of the resection occurs while dissecting tumor in the retrosellar space.2 Meningiomas of neighboring regions such as those of the tuberculum, anterior clinoid process, or petrous apex, all arise from above the membrane of Liliequist which provides a plane of tumor dissection from the neurovascular structures of the posterior fossa. Posterior clinoid meningiomas arise from beneath this arachnoidal membrane and thus lack its protection while dissecting tumor from the basilar artery and its perforators.3,4 Surgical resection of these tumors requires meticulous intra-arachnoidal dissection of the encased basilar artery and its branches, and separation of tumor from the hypothalamus, cranial nerves, pituitary stalk, and brainstem while preserving their vascular supply. The combined petrosal facilitates a wide exposure reaching the entire central skull base for the safe visualization and dissection of tumor along the length of the basilar and the hypothalamus.5,6 The patient is a 68-year-old woman with hemiparesis and seizures from a posterior clinoid meningioma. The tumor was resected using the combined petrosal approach. The patient has consented to surgery and publication of images. {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"VIDEO.","caption":"","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_279na25v"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]}