Tip Of Anterior Clinoid Process Research Articles

The classical supraorbital minicraniotomy to approach the areas of origin of anterior skull base meningiomas: Anatomical nuances influencing accessibility, operability, and frontal lobe retraction.

The classical supraorbital minicraniotomy (cSOM) constitutes a minimally invasive alternative for the resection of anterior skull base meningiomas (ASBM). Surgical success depends strongly on optimal patient selection and surgery planning, for which a careful assessment of tumor characteristics, approach trajectory, and bony anterior skull base anatomy is required. Still, morphometrical studies searching for relevant anatomical factors with surgical relevance when intending a cSOM for ASBM resection are lacking. Bilateral cSOM was done in five formaldehyde-fixed heads toward the areas of origin of ASBM. Morphometrical data with potential relevant surgical implications were analyzed. The more tangential position of the cSOM with respect to the olfactory groove (OG) led to a reduction in surgical freedom (SF) in this area compared to others (P < 0.0001). Frontal lobe retraction (FLR) was also higher when approaching the OG (P < 0.05). Olfactory nerve mobilization was higher when accessing the planum sphenoidale (PS), tuberculum sellae (TS), and anterior clinoid process (ACP) (P < 0.0001). OG depth and the slope of the sphenoid bone between the PS and TS predicted lower SF and higher frontal retraction requirements along the OG and TS, respectively (P < 0.05). In contrast, longer distances to the ACP tip predicted lower SF over this structure (P < 0.01). Although clinical validation is still needed, the present anatomical data suggest that assessing minicraniotomy's position/extension, OG depth, the sphenoid's slope, and distance to ACP-tip might be of particular relevance to predict FLR, maneuverability, and accessibility when considering the cSOM for ASBM resection, thus helping surgeons optimize patient selection and surgical strategy.

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.

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.

Morphometric Analysis of Anterior Clinoid Process and Optic Strut: A Cadaveric Study

Introduction: Anterior Clinoid Process (ACP) is a bony projection on the posterior border of lesser wing of sphenoid. It is related to optic nerve, internal carotid and ophthalmic arteries. Optic strut (OS) is a bony formation located between upper side of body and lesser wing of sphenoid bone. Aim: To observe the variations in length, width of ACP and location of optic strut on right and left side in dry skulls among South Indian population. Materials and Methods: An observational study was done in the Department of Anatomy, Adichunchanagiri Institute of Medical Sciences, Mandya, Karnataka, India, from August 2021 to December 2021. Total 37 dry skulls were collected from department and also from bone sets from first year MBBS (Bachelor of Medicine and Bachelor of Surgery) students. Various parameters (length, width of ACP, distance from tip of ACP and OS, distance between tips of ACP) were measured on both sides using digital vernier callipers. Independent t-test was applied to compare the means of different groups. Results: Mean width of ACP was 14.86±4.47 mm on right side and 12.71±3.13 mm on left side (p-value 0.019). Mean length was 12.45±2.85 mm on right side and 12.05±3.11 mm on left side (p&gt;0.05). Mean distance from tip of ACP to optic strut was 9.48±2.86 mm on right side and 9.31±3.03 mm on left side (p&gt;0.05).Distance between the tips of ACP ranged from 27.09±28.89 mm and mean was 26.29±3.77 mm. Optic strut was located at anterior two-fifth of ACP on right side in 17 (45.95%) and on left side in 14 (37.83%) of skulls. Conclusion: There was variation in mean width of ACP on right and left side. The knowledge will help in preoperative planning and preventing unnecessary injury to neurovascular structures present in vicinity of anterior clinoid process and optic strut.

Surgical Relevance of Pediatric Anterior Clinoid Process Maturation for Anterior Skull Base Approaches.

Removal of the anterior clinoid process (ACP) can expand anterior skull base surgical corridors. ACP development and anatomical variations are poorly defined in children. To perform a morphometric analysis of the ACP during pediatric maturation. Measurements of ACP base thickness (ACP-BT), midpoint thickness (ACP-MT), length (ACP-L), length from optic strut to ACP tip (ACP-OS), pneumatization (ACP-pneumo), and the presence of an ossified carotico-clinoid ligament (OCCL) or interclinoid ligament (OIL) were made from high-resolution computed-tomography scans from 60 patients (ages 0-3, 4-7, 8-11 12-15, 16-18, and >18 yr). Data were analyzed by laterality, sex, and age groups using t-tests and linear regression. There were no significant differences in ACP parameters by laterality or sex, and no significant growth in ACP-BT or ACP-MT during development. From ages 0-3 yr to adult, mean ACP-L increased 49%, from 7.7 to 11.5 mm. The majority of ACP-L growth occurred in 2 phases between ages 0-3 to 8-11 and ages 16-18 to adult. Conversely, ACP-OS was stable from ages 0-3 to 8-11 but increased by 63% between ages 8-11 to adult. Variations in ACP morphology (OCCL/OIL/ACP-pneumo) were found in 15% (9/60) of scans. OCCL and OIL occurred in patients as young as 3 yrs, whereas ACP-pneumo was not seen in patients younger than 11 yrs. The ACP demonstrates stable thickness and a complex triphasic elongation and remodeling pattern with development, the understanding of which may facilitate removal in patients <12. Clinically relevant ACP anatomic variations can occur at any age.

Anterior Clinoidal Meningiomas: Meningeal Anatomical Considerations and Surgical Implications.

Objective: Surgical removal of anterior clinoidal meningiomas (ACMs) remains a challenge because of its complicated relationship with surrounding meninges, major arteries and cranial nerves. This study aims to define the meningeal structures around the anterior clinoid process (ACP) and its surgical implications.Methods: Five dry skulls and 19 cadavers were used in the anatomical study. Cadavers were prepared as transverse, coronal, and sagittal plastinated sections, and the meningeal architecture around the ACP was studied with dissecting and confocal microscopies. The database of meningiomas in one single center was retrospectively reviewed, and the patients with ACMs were collected for clinical analysis.Results: The superior, lateral, medial surfaces, and the tip of ACP were covered by different layers and types of meninges. The ACMs were classified into four main types based on the sites of origin, possible extending pathways following meningeal dura. In the retrospective cohort of 131 ACMs, the percentage of types I, IIa, IIb, III, and IV were 42.0% (55/131), 19.8% (26/131), 9.2% (12/131), 16.8% (22/131), and 12.2% (16/131), respectively. We found that types IIa and I had higher chances for achieving Simpson grade 1–2 resection (92.3 and 85.4%, respectively), followed by type III (54.5%) and type IV (31.3%), while type IIb showed little chance of Simpson grade 1–2 resection. Univariate and multivariate analyses revealed ACM classification and tumor size (<3 cm) to be independent risk factors for achieving more extensive resection.Conclusion: The meningeal architecture around the ACP may guide and determine the origin and extension of ACMs. The classification based on the meningeal architecture helps to understand surgical anatomy as well as predicting surgical outcomes.

Prediction of the difficulty of proximal vascular control using 3D-CTA for the surgical clipping of internal carotid artery-posterior communicating artery aneurysms.

During surgical clipping of internal carotid artery (ICA)-posterior communicating artery (PCoA) aneurysms, proximal vascular control (PVC) is difficult to achieve in some cases because of variations in the anatomy of this type of aneurysm and its parent arteries. The authors investigated morphometric features that may be predictive for the necessity of anterior clinoidectomy (ACL) or cervical ICA exposure for PVC. The authors retrospectively reviewed 65 patients with an ICA-PCoA aneurysm treated with clipping during the previous 3 years. The factors considered for assessing the difficulty of attaining PVC included the following: the maximum diameter of the aneurysm; the distance between the tip of the anterior clinoid process (ACP) and the proximal aneurysmal neck; the presence of calcification at the ophthalmic segment of the ICA; and the angles between the communicating segment of the ICA and the ophthalmic segment of the ICA and a line perpendicular to the cranial base, which reflect the tortuosity of the ICA. These parameters were measured based on preoperative CTA results. In a total of 21 patients (32.3%), PVC was difficult to perform with the usual pterional approach. In 6 patients, temporary artery occlusions (TAOs) were difficult to achieve because of severe atherosclerotic wall changes in the ophthalmic segment of the ICA. For 15 patients, the ACPs overhanging the ophthalmic segment of the ICA obstructed the ability to secure a space for TAO. In the 21 patients with PVC difficulty, ACL alone, cervical ICA exposure alone, and both ACL and cervical ICA exposure were conducted in 6, 8, and 7 patients, respectively. Multivariate analysis with binary logistic regression revealed that the maximum diameter of the aneurysm (p = 0.041), the distance between the proximal neck of the aneurysm and the ACP tip (p = 0.002), and calcification of the ICA ophthalmic segment (p = 0.001) were significant predictive factors for difficulties with PVC. A receiver operating characteristic curve analysis revealed that a distance between the proximal aneurysmal neck and the ACP tip of ≤ 5.4 mm was the best cutoff value for predicting the difficulty of attaining PVC (area under the curve 0.800, sensitivity 80.0%, specificity 80.0%). A short distance between the proximal aneurysmal neck and the ACP tip and the presence of calcification at the ophthalmic segment of the ICA on preoperative CTA are helpful for predicting the difficulty of achieving PVC.

Endoscopic endonasal anterior clinoidectomy: surgical anatomy, technique nuance, and case series.

Advances in endoscopic technique allow for resection of the anterior clinoid process (ACP) via an endoscopic endonasal approach. The authors discuss the endoscopic endonasal anterior clinoidectomy (EEAC) and demonstrate the relevant surgical anatomy and technical nuances. The approach was simulated in 6 cadaveric heads. From a technical point of view, the lateral optic carotid recess was used as the landmark in the proposed technique. The superomedial, superolateral, and inferior vertices of this recess are the main operative points. The EEAC approach was achieved by disconnecting the ACP tip from the base by drilling the 3 vertices. The proposed approach was successfully performed in all cadaveric specimens. Then, in a case series involving 6 patients in whom the EEAC approach was used, there were no vascular injuries; 2 patients had postoperative oculomotor nerve palsy, which improved in one and resolved in the other by 1 month.The EEAC approach for tumors and vascular lesions in the parasellar region is technically feasible. The surgical corridor is increased by ACP resection, although to a lesser extent than the transcranial anterior clinoidectomy. Based on the authors' initial anatomical and surgical results, resection of the ACP via the endonasal endoscopic approach is a novel technique worth exploring in suitable cases.

Abstract WP128: Preoperative Prediction of the Necessity for Anterior Clinoidectomy during Microsurgical Clipping of Posterior Communicating Artery Aneurysms

Background: Although most posterior communicating artery (PCoA) aneurysms can be clipped easily with excellent results, some require anterior clinoidectomy for safe and complete clipping. Objectives: To review our microsurgical series of ruptured PCoA aneurysms and identify the preoperative predictors for anterior clinoidectomy during microsurgical clipping for PCoA aneurysms Methods: Results from microsurgical clipping of 104 patients with ruptured PCoA aneurysms were retrospectively reviewed. Distances and angles were obtained from computed tomographic angiography and compared between the anterior and non-anterior clinoidectomy groups. Result: Anterior clinoidectomy was required in 19 of the 104 cases (18%). None developed surgical complications due to anterior clinoid process (ACP) resection, including postoperative visual deficit. Univariate and multivariate analyses revealed that the distances from the ACP tip to the aneurysmal proximal neck and from the ACP line to the aneurysmal proximal neck were statistically significant predictive factors for the need of anterior clinoidectomy. Based on a receiver operating characteristic (ROC) analysis, the distances from the ACP tip to the aneurysmal proximal neck &lt; 4.0 mm and from the ACP line to the aneurysmal proximal neck &lt; 2.0 mm were selected as optimal cut-off values for predicting the necessity of anterior clinoidectomy, and the area under the ROC curve values were 0.991 and 0.955, respectively. Conclusion: In case of ruptured PCoA aneurysm surgery, the distances from the ACP tip to the aneurysmal proximal neck and from the ACP line to the aneurysmal proximal neck were both found to be useful predictors of whether anterior clinoidectomy was required.

Preoperative Prediction of the Necessity for Anterior Clinoidectomy During Microsurgical Clipping of Ruptured Posterior Communicating Artery Aneurysms.

Although most posterior communicating artery (PCoA) aneurysms can be clipped easily with excellent results, some require anterior clinoidectomy for safe and complete clipping. To review our microsurgical series of ruptured PCoA aneurysms and identify the preoperative predictors for anterior clinoidectomy during microsurgical clipping for PCoA aneurysms. Results from microsurgical clipping of 104 patients with ruptured PCoA aneurysms were reviewed retrospectively. Distances and angles were obtained from computed tomographic angiography and compared between the anterior and nonanterior clinoidectomy groups. Anterior clinoidectomy was required in 19 of the 104 cases (18%). None developed surgical complications due to anterior clinoid process (ACP) resection, including postoperative visual deficit. Univariate and multivariate analyses revealed that the distances from the ACP tip to the aneurysmal proximal neck and from the ACP line to the aneurysmal proximal neck were statistically significant predictive factors for the need of anterior clinoidectomy. Based on a receiver operating characteristic analysis, the distances from the ACP tip to the aneurysmal proximal neck <4.0 mm and from the ACP line to the aneurysmal proximal neck ≤2.0 mm were selected as optimal cutoff values for predicting the necessity of anterior clinoidectomy, and the area under the receiver operating characteristic curve values were 0.991 and 0.955, respectively. In case of ruptured PCoA aneurysm surgery, the distances from the ACP tip to the aneurysmal proximal neck and from the ACP line to the aneurysmal proximal neck were both found to be useful predictors of whether anterior clinoidectomy was required.

Morphometric Study of Anterior Clinoid Process and Optic Strut and the Ossification of Carotico-Clinoid Ligament with their Clinical Importance

Knowledge about the ossification of the Carotico-Clinoid Foramen (CCF), as it forms a potential site for compression of the internal carotid artery may be beneficial for neurosurgeons and radiologists. To obtain a detailed knowledge of morphometry of Anterior Clinoid Process (ACP) and Optic Strot (OS) and the type of ossification of CCF which would be necessary to increase the success of surgeries related to the cavernous sinus and internal carotid artery. Parameters such as the length of ACP from its base to the tip, the width at its base and the distance between the tip of ACP to optic strut were measured in mm using digital calipers. SPSS version 17 was used for the statistical analysis. Paired t-test was applied to compare between right and left sides. Presence of carotico-clinoid foramen was observed and was classified as incomplete, contact form or complete. The average length of ACP ranged from 12 to 15mm on right side and 11 to 16mm on the left side. Paired t-test was applied to compare the means between the right and left sides. The width of ACP varied between right and left sides and this difference was statistically significant (p<0.05). Out of 12 CCF observed, the commonest type was incomplete (N=7) followed by complete (N=3) and contact form (N=2). Considering the immense anatomical surgical and radiological importance of morphology of ACP, OS and CCF, this study highlighted the detailed morphometry of these structures. The study also has explained the sexual dimorphism in their morphology.