Anterior Clinoidal Meningiomas: Meningeal Anatomical Considerations and Surgical Implications.

Tao Xu,Ming Zhang,Lei Jiang,Zhenyu Gong,Alexander I Evins,Yicheng Lu,Li Cai,Juxiang Chen,Huaiyu Sun,Hongxiang Wang,Weiqing Li,Yong Yan

doi:10.3389/fonc.2020.00634

Abstract

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.

Highlights

Anterior clinoidal meningiomas (ACMs) were first reported in 1938 and compose about 34.0–43.9% of all sphenoid wing meningiomas [1]
Few reports revealed the fine architecture of the meningeal coverings of the anterior clinoidal process (ACP), and few of the previously proposed classifications of ACMs differentiated the underlying relationship between the meningeal architecture and surgical implications
Area IV was the medial surface of ACP that was adjacent to the optic canal anteromedially and the internal carotid artery (ICA) posteromedially

Summary

Introduction

Anterior clinoidal meningiomas (ACMs) were first reported in 1938 and compose about 34.0–43.9% of all sphenoid wing meningiomas [1]. ACMs originate from the meninges attached to the anterior clinoidal process (ACP) and extend along the meningeal dura as they grow larger, displacing or even invading the surrounding neurovascular structures [2]. There were several anatomical studies on the ACP and its surrounding structures, especially the cavernous sinus and the carotid artery [6,7,8,9]. Few reports revealed the fine architecture of the meningeal coverings of the ACP, and few of the previously proposed classifications of ACMs differentiated the underlying relationship between the meningeal architecture and surgical implications

Methods

Results

Discussion

Conclusion