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Table of Contents    
COMMENTARY
Year : 2016  |  Volume : 64  |  Issue : 3  |  Page : 476-477

Medial sphenoid wing meningioma


Department of Neurosurgery, Nanavati Super Speciality Hospital, Mumbai, Maharashtra, India

Date of Web Publication3-May-2016

Correspondence Address:
Suresh Sankhla
Department of Neurosurgery, Nanavati Super Speciality Hospital, Mumbai, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.181566

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How to cite this article:
Sankhla S. Medial sphenoid wing meningioma. Neurol India 2016;64:476-7

How to cite this URL:
Sankhla S. Medial sphenoid wing meningioma. Neurol India [serial online] 2016 [cited 2019 Aug 17];64:476-7. Available from: http://www.neurologyindia.com/text.asp?2016/64/3/476/181566


Cushing and Eisenhardt described sphenoid wing meningiomas more than 75 years ago and categorized these globoid tumors into 3 groups based on their location and origin from the medial, middle, or lateral segments of the lesser wing of sphenoid, respectively.[1] The meningiomas that arise from the medial region of the sphenoid present more challenges for neurosurgeons, given their proximity to the optic nerve, the internal carotid artery and its branches, the cranial nerves entering the superior orbital fissure, and the cavernous sinus (CS). This subgroup of sphenoid wing meningiomas, thus, represents the most complex tumors and is associated with a comparatively higher incidence of postoperative morbidity and tumor recurrence.

In this retrospective study of 78 consecutive patients with medial sphenoid wing meningiomas, Verma et al., from AIIMS, New Delhi, have discussed the surgical nuances and have tried to point out that there are differences in the clinical manifestations, surgical techniques, and postoperative morbidity between the group of patients who have medial sphenoid wings meningiomas without (Group 1) and with (Group 2) cavernous sinus involvement.[2]

The surgical philosophy of these tumors has been constantly evolving. The treatment strategy has changed from aggressive tumor resection in the 1980's to a maximal safe resection and radiosurgery in the recent years.[3] The roles of adjunctive therapy and simple observation are very well defined in the present literature, and both methods appear to be the valid treatment options in selected cases. The surgical challenges associated with large or giant tumors are special and include the risks involved in locating, dissecting, and preserving the critical neurovascular structures that they inevitably involve or encase. The difficulties are increased by a tense brain, secondary edema, and mass effect due to the tumor. The best way to deal with these problems is to obtain an appropriate skull base exposure (fronto-temporal craniotomy with orbitozygomatic osteotomy) and to perform an extradural bone drilling (anterior clinoidectomy, unroofing of the optic canal, and removal of the hyperostotic bone).

The issue of the surgical approach undertaken is important. We agree that a simple pterional craniotomy may not be adequate in all cases of large or giant tumors with severe brain edema and mass effect. From a variety of the available anterior skull base approaches, the most appropriate exposure should be tailored to the individual situation. One must also be aware of the several variations of the cranio-orbito-zygomatic approach, which should be applied as and when required. Removal of the orbital rim generally permits a steep angulation in the surgical viewing of the operative field from the inferior towards the superior aspect, thus, resulting in reduced brain retraction. Resection of a part of the orbital roof posteriorly, on the other hand, offers important advantages like uncovering the periorbita, exposing the superior orbital fissure, and in facilitating interdural dissection of the cavernous sinus. It also helps during decompression of the optic nerve and exposure of the tumors situated in the posterior part of the orbit. The zygomatic part of the orbitozygomatic approach can be used when needed to obtain an additional exposure of the temporal and infratemporal regions.

The extradural bony drilling at the skull base is a very crucial step and has been described very well by Verma et al., in this issue.[2] The concept of an extradural approach to the skull base is not new. After the pioneering work by Dolenc,[4] who described it for cavernous sinus surgery, the technique has evolved and has been recommended by several authors for the surgical removal of the clinoidal or medial sphenoid wing meningiomas. In the case of a medial sphenoid wing meningioma, the extradural bone removal should include the lesser wing of sphenoid, anterior clinoid process, optic roof and walls, posterior orbital roof, and the adjacent hyperostotic bone. In contrast to the intradural drilling, the extradural technique has several advantages as it avoids direct brain retraction and the risk of chemical meningitis due to the contamination of the cerebrospinal fluid by bone dust. But more importantly, it devascularizes the tumor in the initial part of the operation and helps in easier and faster tumor removal. It also reduces the risk of tumor recurrence as the involved bone at the skull base is removed aggressively. The extradural anterior clinoidectomy has the added advantage of increasing the surgical corridor through the optico-carotid angle. The additional exposure provides the surgeon with multiple trajectories to the tumor and a good visualization of the branches of internal carotid artery (ICA).

Many authors advocate an extradural anterior clinoidectomy and optic canal unroofing that is performed early in the operation as the best way to achieve a favourable visual outcome and good surgical results.[5],[6] The manuever allows early identification and safe dissection of the optic nerve, oculomotor nerve, and internal carotid artery and its branches, which are usually involved or encased by the tumor. In our experience, a good arachnoidal plane is always appreciated between the neurovascular structures and the tumor capsule once the bone has been removed adequately. An early release of the tethered optic nerve in the canal permits its safe manipulation and handling during the subsequent intradural dissection of the tumor. Opening of the optic canal also allows visualization and removal of the intracanalicular tumor extension, which often remains undetected even on the high-quality preoperative MRI study of the brain and orbits.

The authors have described the technique of tumor removal elaborately. Two important points, however, need to be mentioned. Firstly, although vascular encasement is common, and sometimes the arachnoidal plane remains intact enough to dissect the vessel free from the tumor, in many cases the tumor is too firmly adherent to the blood vessel to allow its safe dissection. The tumor in this situation should be shaved off to obtain a thin sheath layering the vessel, to avoid serious vascular injury (the risk of which is as high as 20% in many studies).[7] The residual tumor can later be treated with radiosurgery or fractionated stereotactic radiosurgery, if necessary. However, there is enough evidence in the literature to suggest that many of these tumor remnants undergo growth arrest and do not recur.[5]

The second issue is related to the cavernous sinus involvement by the tumor. We have sufficient experience to propose that conservative treatment is generally the best philosophy when the cavernous sinus is invaded. The rates of successful tumor control with safe resection and adjuvant therapy have generally been good (the control rate achieved is approximately 80% over 7-8 years).[3],[7] However, we believe that the surgeon's assessment during surgery, and not only the preoperative imaging findings, is more important for making of a final decision on whether or not to resect the tumor from within the cavernous sinus. A soft meningioma compressing but not invading the cavernous sinus, or the one that partially involves the cavernous sinus may well be resected with no added deficit or with an acceptable transient oculomotor morbidity. Even when total resection is not safe or feasible, it is essential to consider future planned radiosurgery. Every effort should be made during surgery to create a space between the residual tumor margin and the optic apparatus to allow a safe maximal radiosurgical dosing after surgery.

The report by Verma et al., successfully reinforces what is generally known about the medial sphenoid wing meningiomas.[2] It also highlights how safely and effectively a difficult tumor like this can be treated by innovative and experienced surgeons. I congratulate the authors for sharing with us their experience in the surgical management of medial sphenoid wing meningiomas.

 
  References Top

1.
Cushing H, Eisenhardt L. Meningiomas: Their Classification, Regional Behaviour, Life History, and Surgical End Results. Springfield, IL: Charles C Thomas; 1938.  Back to cited text no. 1
    
2.
Verma SK, Sinha S, Sawarkar DP, Singh PK, Gupta D, Agarwal D, et al. Medial sphenoid wing meningiomas: Experience with microsurgical resection over 5 years and review of literature. Neurol India 2016;64:464-74.  Back to cited text no. 2
    
3.
Sughrue ME, Kane AJ, Shangari G, Rutkowski MJ, McDermott MW, Berger MS, et al. The relevance of Simpson grade I and II resection in modern neurosurgical treatment of World Health Organisation grade I meningioma. Clinical article. J Neurosurg 2010;113:1029-35.  Back to cited text no. 3
    
4.
Dolenc V. Direct microsurgical repair of intracavernous vascular lesions. J Neurosurg 1983;58:824-31.  Back to cited text no. 4
    
5.
Kattner KA, Fukushima T. Management of vascular invasion during radical resection of medial sphenoid wing meningiomas. Skull Base 2001;11:99-104.  Back to cited text no. 5
[PUBMED]    
6.
Morcos JJ. Sphenoid wing meningiomas. J Neurosurg 2013;119:82-4.  Back to cited text no. 6
    
7.
Nakamura M, Roser F, Jacobs C, Vorkapic P, Samii M. Medial sphenoid wing meningiomas: Clinical outcome and recurrence rate. Neurosurgery 2006;58:626-39.  Back to cited text no. 7
    




 

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