Anterior Clinoidal Meningiomas: Meningeal Anatomical Considerations and Surgical Implications

Abstract

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.

The factors influencing postoperative efficacy of anterior clinoidal meningioma treatment and an analysis of best-suited surgical strategies

“…Of the 60 ACM cases reported by Goel et al ( 21 ), 55 had visual defects (91.7%) before surgery; after surgery, 14 (25%) had improved visual acuity. In cases reported by Xu et al ( 3 ) where there was visual deterioration before surgery, 52.6% had visual acuity improvement. In the current study, the postoperative visual acuity prognosis was significantly correlated with the preoperative visual acuity level ( P < 0.01), as shown in Table 5 .…”

“…Nakamura et al ( 12 ) divided ACMs into two groups, but this typing is too simplistic to accurately reflect the surgical difficulty and predict ACM prognosis. Xu et al ( 3 ) divided ACMs into four types, with Type II ACMs being further divided into two subtypes, which becomes too complex. Based on Al-Mefty's classification, in this study, giant ACMs that invaded the cavernous sinus and had a tumor base covering the entire ACP were classified as Type IV.…”

“…② Tumor size: Large tumors are more likely to invade the cavernous sinus or encase and invade the ICA and its branches, and as a result, these factors primarily prevent total ACM resection. According to the analyses conducted by Xu et al ( 3 ), ACM size (< 3 cm) is an independent risk factor for more extensive resection. According to Goel et al ( 21 ), the risk of surgical failure for ACM resection >3 cm is high.…”

Invasive Corridor of Clivus Extension in Pituitary Adenoma: Bony Anatomic Consideration, Surgical Outcome and Technical Nuances

“…In this study, we researched the relationship between the cancellous bone corridor and PA invasion using microsurgical dissection and the recently developed epoxy sheet plastination technique. The plastination technique uses durable and transparent resin to replace water and fat in tissues and cells, thus keeping all the neural and vascular structures in their natural state in situ without decalcification (11,24,25). The combination of plastination and microsurgical dissection is a good way to explore the extent of cancellous bone within the clivus.…”

Morphometric Analyses of the Caroticoclinoid and Interclinoid Foramina: A Study in Brazilian Dry Skulls

“…The ACP is a posteromedial bony projection of the lesser wing of the sphenoid bone and the lateral wall of the optic canal, having three fixations: one medial, to the sphenoid plane, one laterally, on the lesser wing of the sphenoid bone and one inferomedial, forming the optic strut (Chaddad-Neto et al, 2020). Additionally, it is possible to divide the ACP into four distinct areas -the medial, lateral, superior, and posterior triangle (Xu et al, 2020).…”