Measurement of Critical Structures around Paraclinoidal Area : A Cadaveric Morphometric Study

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.

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

OBJECTIVE

This study aimed to peruse the alteration of the position of the optic strut (OS) according to the anterior clinoid process (ACP) pneumatization.

METHODS

This retrospective study conducted on cone-beam computed tomography images of 400 patients with a mean age of 36.49±15.91 years.

RESULTS

Anterior clinoid process length, width, and angle were measured as 10.56±2.42 mm, 5.46±1.31 mm, and 42.56±14.68 degrees, respectively. The tip of ACP was measured as 6.60±1.50 mm 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%).

CONCLUSIONS

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.

Extradural anterior clinoidectomy through endoscopic transorbital approach: laboratory investigation for surgical perspective

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.

Intra- and extradural anterior clinoidectomy: anatomy review and surgical technique step by step

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.

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.

Anterior clinoidectomy using an extradural and intradural 2-step hybrid technique

In Brief: The authors found a practical intraoperative landmark to localize the optic strut during anterior clinoidectomy and used it as the basis for performing anterior clinoidectomy in two steps: extradural phase and intradural phase. This anatomically based technique can increase the safety of anterior clinoidectomy by providing easily identifiable landmarks and reducing intradural bone drilling, which could put the adjacent neurovauscular structures at risk.

Incidence and morphometry of caroticoclinoid foramina in Greek dry human skulls

BACKGROUND

Ossification of the caroticoclinoid ligament (CCL) and formation of a caroticoclinoid foramen (CCF) may impose significant risk to neurosurgeons by impeding mobilization of the cavernous segment of the internal carotid artery. Although safe surgical access to the clinoidal space is related to understanding the CCF anatomical and ethnic variants, there remains a paucity of studies of the morphology and bony relationships. The current study provides a systematic morphological and morphometric analysis of the CCF, the ossification of the CCL extending between the anterior and middle clinoid processes, and their relations in a Greek population.

MATERIALS AND METHODS

The incidence of unilateral and bilateral CCF, types (complete, incomplete, and contact) of ossified CCLs, and foramina diameter according to side and gender were determined in 76 Greek adult dry skulls. Findings were correlated with the morphology of optic strut (OS) (presulcal, sulcal, postsulcal, and asymmetric).

RESULTS

A CCF was detected in 74% of the specimens. The majority of skulls (51.4%) had bilateral CCF, whereas 22.3% of the skulls had unilateral foramina. Incomplete CCF were observed in 69.3%, complete in 19.8%, and contact type in 10.9%. The mean CCF diameter was 0.55 ± 0.07 cm on the left and 0.54 ± 0.08 cm on the right side. Side symmetry existed, although there were no significant differences according to gender. The CCF were more prominent in skulls with a sulcal type of OS.

CONCLUSIONS

The results of the present study augment the current knowledge on the morphology of key anatomical landmarks, CCF, and CCL ossification in the sellar area, indicating population differences. A significant side asymmetry in caroticoclinoid osseous bridging and foramina is highlighted. These findings are necessary for a safe surgical access to the clinoidal area.

Extradural anterior clinoidectomy in the management of parasellar meningiomas: Analysis of 13 years of experience and literature review

BACKGROUND AND AIM

The extradural anterior clinoidectomy (EAC) is a key microsurgical technique that facilitates the resection of tumors located in the parasellar region. There is currently no consensus regarding the execution of the procedure via extradural or intradural nor scientific evidence that supports its routine use. The purpose of this article is to expose our experience in performing EAC as part of the management of the parasellar meningiomas.

MATERIALS AND METHODS

A retrospective analysis of the EAC for parasellar meningioma resection performed in our center between 2003 and 2015 was done. A total of 53 patients were recorded. We analized our series focusing on visual outcomes, resection rates and complications. Through an extensive bibliographic research, we discussed the advantages and disadvantages of the EAC, technical considerations, comparison with the intradural clinoidectomy and its visual impact.

RESULTS

The most frequent tumors were anterior clinoidal meningiomas (33.9%). The most common initial symptoms were decreased visual acuity (45.3%) and headache (22.6%). A gross total resection was achieved in 67.9%, being subtotal in the remaining 32.1%. Regarding the visual deficits 67.9% of the patients presented clinical stability, 22.6% improvement and 9.4% worsening. The degree of tumor resection did not significantly influence post-surgical visual outcomes, either visual acuity (P=.71) or campimetric alterations (P=.53). 24.5% of the patients experienced iiinerve transient paresis and 1.9% permanent. The postoperative cerebrospinal fluid leak rate was 3.8%. Mortality rate was 0%. The mean follow-up was 82.3 months.

CONCLUSIONS

In our experience, EAC is a safe technique that facilitates the resection of the meningiomas located in the parasellar area, helps to achieve early tumor devascularization, reduces the need for retraction of the cerebral parenchyma and could play a positive role in the preservation of visual function and the appearance of tumor recurrences in the anterior clinoid process (ACP).

Optic nerve injury-associated blunt cerebrovascular injury: Three case reports

RATIONALE

Blunt cerebrovascular injury (BCVI) is a rare complication that may occur after craniocervical trauma. The current literature is limited to extracranial carotid artery injuries; however, no reports have been published on blunt intracranial carotid injury (BICI), especially those associated with optic nerve injury.

PATIENT CONCERNS

Here we report on 3 BICI cases that demonstrated optic nerve injuries after craniofacial injuries. All 3 patients showed post-trauma vision loss on the injured side.

DIAGNOSES

Optical canal fractures can be found in these patients, and carotid sulcus was compressed by the fragments. Computed tomography angiography (CTA) and digital subtraction angiography (DSA) were performed in all 3 patients.

INTERVENTIONS

Case 1 was given no further treatment, except for symptomatic support and rehabilitation therapy. Case 2 was treated with antiplatelet therapy for 3 days, and then a stent was inserted in the injured internal carotid. Case 3 received antiplatelet therapy and a internal carotid compression test was performed simultaneously for 2 weeks, then the injured internal carotid was completely blocked.

OUTCOMES

Case 1 developed cerebral infarction that resulted in unilateral hemiplegia. Due to timely treatment, the remaining 2 patients had a better prognosis.

LESSONS

CTA should be performed primarily to exclude vascular injury and for CTA-positive patients, a further DSA should be performed to investigate pathological changes and for a definitive diagnosis. At last, the current therapeutic protocols for BCVI are not entirely applicable to intracranial vascular injury, and appropriate protocols for the treatment of BICI should be selected based on the combination of test results and the actual condition of the patient.

Internal Carotid Artery Aneurysm Anomalously Originating from the Posterior Communicating Artery

BACKGROUND

We report a case of an internal carotid artery (ICA) aneurysm anomalously originating from the posterior communicating artery (PComA).

CASE DESCRIPTION

Preoperative radiologic findings revealed a paraclinoid carotid artery aneurysm at the level of the distal dural ring. Because of the low rupture risk, there are no treatment indications for small paraclinoid or ICA-superior hypophyseal artery unruptured aneurysms. In this case, because of the patient's age and the irregular shape of the aneurysm, treatment was considered necessary. Intraoperative findings using microscopic and endoscopic angiography showed that the aneurysm originated from the proximal branched PComA. The PComA originated from the same level as the ophthalmic artery, and the superior hypophyseal artery originated from the distal side of the PComA.

CONCLUSIONS

According to numerous reports, small incidental paraclinoid aneurysms have a lower risk of rupture and growth than PComA aneurysms. Preoperative radiologic examination of unruptured small aneurysms was performed using magnetic resonance angiography and three-dimensional computed tomography angiography. Because the ability of magnetic resonance angiography and three-dimensional computed tomography angiography to detect small branches of the ICA is inferior to digital subtraction angiography, the location of an unruptured ICA aneurysm should be evaluated with other diagnostic modalities besides magnetic resonance angiography and three-dimensional computed tomography angiography.