Anterior clinoid region meningioma

see also Tuberculum sellae meningioma.

Medial sphenoid wing meningioma of the anterior clinoid process are uncommon tumors, acknowledged by most experienced surgeons to be among the most challenging meningiomas to completely remove due to their propensity to encase the internal carotid artery (ICA) and its branches, and invade the cavernous sinus and the optic canal 1) 2) 3) 4).

In many cases, the tumor is densely adherent to the carotid artery, rendering complete tumor removal impossible, even in experienced hands 5) 6) 7) 8).

Meningiomas of the anterior clinoid process may infiltrate the bone over which they arise, therefore requiring an anterior clinoidectomy to achieve a Simpson Grading System 1 resection. A clinoidectomy, however, is not without risks.

Anterior clinoidal meningiomas are frequently grouped with suprasellar meningioma or sphenoid ridge meningiomas, masking their notorious association with a high mortality and morbidity rate, failure of total removal, and recurrence. To avoid injury to encased cerebral vessels, most surgeons are content with subtotal removal. Without total removal, however, recurrence is expected. Recent advances in cranial-base exposure and cavernous sinus surgery have facilitated radical total removal. The author reports 24 cases operated on with vigorous attempts at total removal of the tumor with involved dura and bone. This experience has distinguished three groups (I, II, and III) which influence surgical difficulties, the success of total removal, and outcome. These subgroups relate to the presence of interfacing arachnoid membranes between the tumor and cerebral vessels. The presence or absence of arachnoid membranes depends on the origin of the tumor and its relation to the naked segment of carotid artery lying outside the carotid cistern. Total removal was impossible in the three patients in Group I, with postoperative death occurring in one patient and hemiplegia in another. Total removal was achieved in 18 of the 19 patients in Group II, with one death from pulmonary embolism. In the two patients in Group III, total removal without complications was easily achieved 9).

A cavernous hemangioma presenting as a clinoid meningioma is extremely rare.

A 36-year-old male with an asymptomatic intracranial mass found incidentally after an ATV accident. Preoperative MRI revealed a well-defined dural-based lesion arising from the right anterior clinoid process which was nearly homogenously enhancing, with a radiological diagnosis of meningioma. The mass was resected via right pterional craniotomy with microsurgical technique. Complete resection of the mass was performed with no complications and, notably, no significant bleeding. Contrasting with the radiologic and gross tumor appearance, histopathologic examination revealed dilated vascular spaces, sclerotic vessels without intervening neural tissue, and intravascular thrombi suggesting slow blood flow - all consistent with cavernous hemangioma.

Anterior clinoid dural-based cavernous hemangioma are extremely rare. Though preoperative diagnosis is difficult using imaging, this etiology should be considered for any dural-based middle fossa lesion due to the tendency for these lesions to bleed heavily during resection in some instances 10).

It is hard to argue that any group of skull base meningiomas represent a unified group of uniform pathologic anatomy. While some skull base meningiomas present as a localized mass, others present as a diffuse mass, infiltrating the cavernous sinus, encasing vessels, and invading cranial nerve foramina. Most skull base surgeons are well aware that not all clinoid meningiomas are the same. However, due to the rarity of these lesions, it has been difficult to sub-stratify and sub-analyze these lesions differently based on differing radiographic features. Thus, the literature to date has generally not analyzed outcomes for clinoidal meningiomas in the same way that skull base surgeons think of them when they are planning an operation 11).

Clinoidal meningiomas. Al-Mefty O. J Neurosurg. 1990;73:840–849.
Clinoidal meningiomas. Al-Mefty O, Ayoubi S. Acta Neurochir Suppl (Wien) 1991;53:92–97.
Anterior clinoidal meningiomas: report of a series of 33 patients operated on through the pterional approach. Puzzilli F, Ruggeri A, Mastronardi L, Agrillo A, Ferrante L. Neuro Oncol. 1999;1:188–195.
4) , 5)
Meningiomas involving the anterior clinoid process. Risi P, Uske A, de Tribolet N. Br J Neurosurg. 1994;8:295–305.
Surgical management of clinoidal meningiomas. Lee JH, Jeun SS, Evans J, Kosmorsky G. Neurosurgery. 2001;48:1012–1019.
A surgical technique for the removal of clinoidal meningiomas. Lee JH, Sade B, Park BJ. Neurosurgery. 2006;59:0–14.
Management of surgical clinoidal meningiomas. [Mar;2015 ];Tobias S, Kim CH, Kosmorsky G, Lee JH. Neurosurg Focus. 2003 14:0.
Al-Mefty O. Clinoidal meningiomas. J Neurosurg. 1990 Dec;73(6):840-9. Review. PubMed PMID: 2230967.
Mansour TR, Medhkour Y, Entezami P, Mrak R, Schroeder J, Medhkour A. The Art of Mimicry: Anterior Clinoid Dural-Based Cavernous Hemangioma Mistaken for a Meningioma. World Neurosurg. 2017 Feb 15. pii: S1878-8750(17)30191-2. doi: 10.1016/j.wneu.2017.02.029. [Epub ahead of print] PubMed PMID: 28214640.
Sughrue M, Kane A, Rutkowski MJ, Berger MS, McDermott MW. Meningiomas of the Anterior Clinoid Process: Is It Wise to Drill Out the Optic Canal? Cureus. 2015 Sep 10;7(9):e321. doi: 10.7759/cureus.321. PubMed PMID: 26487997.
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