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

Treatment of Unruptured Large and Giant Paraclinoid Aneurysms in Japan at the Time of Flow Diverter Introduction: A Nationwide, Multicenter Survey by the Japanese Society on Surgery for Cerebral Stroke

OBJECTIVE

Large or giant paraclinoid aneurysms have been treated with various strategies, including clipping, coiling, and parent artery occlusion (PAO). In addition, flow diverters (FDs) have been introduced for the management of these aneurysms. The aim of this study was to examine the management of unruptured large/giant paraclinoid aneurysms in Japan when FDs were being introduced by a nationwide survey.

METHODS

A total of 576 unruptured large/giant paraclinoid aneurysms treated in Japan between January 2012 and December 2016 were retrospectively studied.

RESULTS

Half of the large paraclinoid aneurysms were treated by coiling (50.3%), whereas giant aneurysms were occluded mainly by PAO (51.4%). A high nearly complete occlusion rate was achieved with clipping (94.1%), coiling (85.9%), PAO (82.4%), and FDs (77.6%). Coiling had higher risks of recurrence (28.3%) and retreatment (20.3%). Major procedure-related complications were observed in 9.7%. Ischemic complications were common in PAO (9.5%), with cranial nerve symptoms common in clipping (10.9%). All treatment modalities achieved good clinical outcomes (93.5%-96.6%). Although not significant, pre-existing visual disturbance improved most frequently by clipping (53.7%), but also worsened most frequently by clipping (24.4%). Consequently, FD achieved a high occlusion rate with minimal complication and retreatment rates.

CONCLUSIONS

All treatment modalities offer high rates of complete occlusion and good clinical outcomes. Coiling has the disadvantage of high rates of recurrence and retreatment. Clipping and PAO have the disadvantage of a high rate of major procedure-related complications; however, PAO can provide comparable treatment outcomes even in cases with refractory giant aneurysms. FDs are the optimal choice for the management for large/giant paraclinoid aneurysms due to its safety and efficacy.

Pterional Craniotomy With Anterior Clinoidectomy for the Resection of a Sphenoid Ridge Meningioma: A Case Report and Two-Dimensional Operative Video

The pterional craniotomy with anterior clinoidectomy is a surgical technique used to resect sphenoid ridge meningiomas. It involves drilling the bone of the anterior clinoid process to gain access to the skull base, including the cavernous sinus and petrous apex particularly. This approach offers several advantages, including excellent exposure of the surgical site, minimal brain retraction, and the ability to visualize and protect critical neurovascular structures. We present a case of a 59-year-old woman presented with headache, dizziness, blurry vision, and unsteady gait for several months. The brain magnetic resonance imaging with gadolinium contrast showed a large space-occupying homogeneously-enhancing lesion at the left skull base, displacing the surrounding structures, including the frontal lobe, temporal lobe, and brainstem. Herein, we present the intraoperative video on a case in which the pterional craniotomy with anterior clinoidectomy that can allow the exposure and resection of the tumor extending into the posterior fossa was utilized for the resection of a large left sphenoid ridge meningioma with brain stem compression.

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.

Clipping of Bilateral Ophthalmic Artery Aneurysms Through a Single Craniotomy

Bilateral ophthalmic aneurysms are rare and involve two aneurysms in the ophthalmic arteries, one on each, leading to potential symptoms such as vision loss and headaches. The treatment options for aneurysms, ranging from surgery and endovascular embolization to observation, depend on various factors, including aneurysm size and the patient's health. Microsurgery, while presenting complexities due to the intricate anatomy of the anterior clinoid region, offers potential advantages such as enhanced decompression rates and reduced aneurysm recurrence. The presented surgical video illustrates the treatment of bilateral ophthalmic artery aneurysms via a single craniotomy. This method reduces surgical duration and trauma, facilitating quicker patient recovery. However, this method bears potential risks, especially to both optic nerves. As underscored in the video, the utmost anatomical understanding in the anterior clinoid area is pivotal for successful outcomes and reduced complications.

Surgical Anatomy of the Microscopic and Endoscopic Transorbital Approach to the Middle Fossa and Cavernous Sinus: Anatomo-Radiological Study with Clinical Applications

BACKGROUND

The transorbital approaches (TOAs) have acquired growing notoriety, thanks to their ability to offer alternative corridors to the skull base. However, the limited access and the unfamiliarity with this surgical perspective make recognition of key landmarks difficult, especially for less experienced surgeons. The study wants to offer a detailed description of the anatomy to comprehend the potential and limitations of TOAs.

METHODS

Measurements of the orbit region and the surrounding areas were performed on two hundred high-resolution CT scans and thirty-nine dry skulls. Five specimens were dissected to illustrate the TOA, and one was used to perform the extradural clinoidectomy. Three clinical cases highlighted the surgical applications.

RESULTS

A step-by-step description of the key steps of the TOA was proposed and a comparison with the transcranial anterior clinoidectomy was discussed. The mean work distance was 6.1 ± 0.4 cm, and the lateral working angle increased 20 ± 5.4° after removing the lateral orbital rim.

CONCLUSIONS

TOAs are indicated in selected cases when tumor involves the lateral portion of the cavernous sinus or the middle skull base, obtaining a direct decompression of the optic nerve and avoiding excessive manipulation of the neurovascular structures. Comprehension of surgical anatomy of the orbit and its surrounding structures is essential to safely perform these approaches.

Microsurgical and illustrative anatomy of the cavernous sinus, middle fossa, and paraclival triangles: a straightforward, comprehensive review

The middle fossa, cavernous sinus, and paraclival triangles consist of ten triangles. Their use in a surgical approach is vast; most are used as landmarks to access and identify other structures of surgical interest. Multiple labels, borders, and contents mentioned by different authors make understanding and reproduction challenging and confusing. This study aims to organize and clarify recent or most relevant publications and disclose our portrayal of the ten triangles using cadaveric dissection and simple and practical figures. Four middle fossa triangles, four cavernous sinus triangles, and two paraclival triangles were dissected and delineated in a cadaveric specimen. Drawings were simplified to eliminate confusion and evaluate the triangles effortlessly. Similarities and differences in triangle names, border limits, and contents are described in a precise form. The recognition of triangle landmarks allows for treating pathologies in a frequently distorted anatomy or challenging to access structure. That is why an accurate knowledge of the surgical anatomy should be mastered, and a safe approach should be accomplished.

Tailored Surgical Access to the Cavernous Sinus and Parasellar Region: Assessment of Cavernous Sinus Entry Corridors and the Periclinoid and Pericavernous Surgical Maneuvers

BACKGROUND

Lesions involving the cavernous sinus (CS) represent some of the most challenging pathologies of the skull base owing to the dense traversing and surrounding neurovasculature. Extradural exposure and preparation of this region, whether as initial preparation for a combined intra-extradural approach or as the main avenue of surgical exposure, can enlarge surgical corridors and minimize the need for brain retraction in this very confined space. We provide a detailed assessment of the entry corridors to the CS that are available within each approach, the surgical exposure and freedom provided by each of these corridors, and demonstrate how extradural and intradural preparation of these corridors can be used to widen the available working space and facilitate surgery.

METHODS

Pterional, frontotemporal-orbital, frontotemporal-orbitozygomatic, frontotemporal-zygomatic, perilabyrinthine transtentorial, and endoscopic transnasal transsphenoidal approaches were performed on cadaveric heads to access the perisellar and CS regions. Periclinoid maneuvers (extradural cutting of the meningo-orbital band, anterior clinoidectomy, unroofing of the optic canal, opening of the superior orbital fissure, displacement of the extra-annular structures, opening of the annulus of Zinn, and interdural dissection), pericavernous maneuvers (intradural cutting of the distal dural ring, mobilization of the supraclinoid internal carotid artery, opening of the oculomotor porus, and mobilization of cranial nerve (CN) III), peritrigeminal extensions (extradural mobilization of CN V2 [maxillary] and/or V3 [mandibular]), and other surgical maneuvers were performed and evaluated. The CS was divided into 8 anatomical compartments and 9 entry corridors were described, and exposure and freedom were assessed accordingly.

RESULTS

Intradurally, the standard unextended pterional, frontotemporal-orbital, and frontotemporal orbitozygomatic transsylvian approaches provided access solely to the parasellar entry corridor into the superior wall of the CS. Expanding these approaches with extradural periclinoid maneuvers allowed for subsequent application of the intradural pericavernous maneuvers and enlargement of the parasellar corridor and exposure of the carotid cave. Extradurally, the frontotemporal-orbital approach could be expanded via application of periclinoid maneuvers, which provided access to the anterior portions of the main lateral wall entry corridors. The frontotemporal-orbitozygomatic approach could also be expanded with periclinoid maneuvers to provide extradural access to all 6 lateral wall entry corridors. The extradural frontotemporal-zygomatic approach only provided exposure following interdural dissection, which allowed for access to the inferolateral entry corridors into the lateral wall. Extradural peritrigeminal extension in the frontotemporal-orbitozygomatic and frontotemporal-zygomatic approaches allows for enlargement of the supramaxillary and pre- and postmandibular corridors. The perilabyrinthine approach to the posterior wall was enlarged with opening of Dorello's canal and the endoscopic transnasal transsphenoidal approach was enlarged with opening of the optic canal.

CONCLUSIONS

Targeted extradural preparation optimizes exposure and significantly improves access to deep-seated targets by enhancing surgical maneuverability through the unlocking of neurovascular structures and widening of surgical corridors without the need for additional brain retraction.