**1. Introduction**

As early as 1922, Harvey Cushing distinguished two types of meningiomas: spherical *en masse* tumors with lobulated and sometimes irregular growth, and *en plaque* tumors, which are slightly elevated from and extend along the inner dural layer [1, 2]. *En plaque* meningiomas are classically associated with significant underlying hyperostosis caused by tumor invasion of the bone and overexpression of osteogenic molecules influencing the osteoblast/osteoclast activity (e.g., osteoprotegerin and insulin-like growth factor 1), [3, 4]. Their preferred location in the pterional region and the sphenoid ridge could be due to the important intraosseous branching of meningeal vessels and venous sinuses at this level [1, 5]. Due to the anatomical complexity of this region, many different names have been used to describe this pathological entity (e.g., *en plaque* sphenoid wing meningioma, *en plaque* pterional meningioma, invading meningioma of the sphenoid ridge, hyperostoting meningioma of the sphenoid ridge, pterional-orbital meningioma…); however, spheno-orbital meningioma (SOM) seems to be both the most appropriate and the most frequently used term [6]. Consequently, SOMs are mainly defined as primary *en plaque* tumors of the lesser and greater sphenoid wings that invade the underlying bone and potentially adjacent anatomical structures [7]. They can progressively extend to the temporal and infratemporal fossae, orbit, anterior clinoid process

(ACP) and cavernous sinus (CS), compromising the integrity of the optic canal, the superior orbital fissure (SOF), and the cranial nerves passing through [8].
