Sphenoid Wing Meningioma
Sphenoid wing meningiomas are slow growing tumors that originate from outer arachnoid meningeal epithelial cells. They are the most common tumor of the intracranial space to spread to the orbit.
- 1 Disease Entity
- 2 Diagnosis
- 3 Management
- 4 Additional Resources
- 5 References
The annual incidence of symptomatic meningiomas is approximately 2 cases per 100,000 individuals. Meningiomas of the anterior skull base constitute 40% of all intracranial meningiomas. Sphenoid wing menigiomas with secondary orbital extension are rare. 
Sphenoid wing meningiomas are slow growing tumors that originate from outer arachnoid meningeal epithelial cells.
Genetically, the most well characterized and common alteration is the loss of the NF2 gene (NF2) on chromosome 22q. NF2 encodes a tumor suppressor known as merlin. Approximately 60% of sporadic meningiomas were found to have mutations in NF2. Meningiomas can also be associated with other genetic syndromes such as Gorlin and Rubinstein-Taybi syndromes, but the association is not as strong as with NF2.
Meningiomas can be multiple, particularly when they associated with neurofibromatosis type 2 (NF2). 
General Pathology and Classification
There is substantial pathologic variation in the appearance of sphenoid wing meningioma specimens. There are many variants encountered including secretory, microcystic, clear cell, lymphoplasmocyte rich, chordoid, atypical, malignant, papillary and anaplastic variants. In general, the typical pathologic features that characterize most meningiomas are whorls of meningothelial cells composed of epithelioid type cells with eosinophilic cytoplasm and ovoid nuclei with or without vacuoles or pseudo-inclusions. Meningiomas may contain calcium deposition in the center of the whorls of cells called psammoma bodies. Figures 1 and 2 represent typical examples of histopathologic specimens of meningiomas.
- WHO Grade I – Includes secretory, microcystic, clear cell, lymphoplasmocyte rich, and chordoid variants. Despite invasion of the adjacent bony structures, grade I meningiomas do not invade the brain parenchyma.
- WHO Grade II – Includes atypical variant. This type of meningioma shows frequent mitosis and an increased nuclear-cytoplasmic ratio.
- WHO Grade III/IV - Includes malignant, papillary and anaplastic variants. This type of meningioma shows even greater mitosis, necrosis, and invasion of brain parenchyma.
In a large retrospective study of 1663 patients who underwent surgery for meningioma, 90% were benign WHO grade I tumors while 10% were atypical or anaplastic variants, WHO grade II or III.
The ophthalmic manifestations of sphenoid wing meningiomas vary depending on the location of the primary tumor. The tumor can extend from the intracranial space into the orbit through bone, the superior orbital fissure or the cavernous sinus. They can present with progressive symptoms of an orbital or temporal fossa mass, including temporal fullness, proptosis, globe displacement, ptosis, and impaired extraocular motility. Tumors near the sella or optic nerve can cause visual field defects, optic disc edema or atrophy. Eyelid edema and chemosis are also commonly encountered. Average age of onset is 50 years with a higher incidence in women and Caucasians.
Imaging of sphenoid wing meningiomas demonstrates a thick homogenous tumor bed with relative sparing of anatomic structures. The tumors are slow growing and have a tendency to conform around structures and cause compression rather than tissue invasion. The average annual growth rate of meningiomas are 1–3 mm per year. On CT, meningiomas are isoattenuating to slightly hyperattenuating and exhibit homogenous and intense enhancement after injection of iodinated contrast. On MRI imaging, T1- and T2-weighted sequences have variable signal intensity, but they enhance intensely and homogeneously after injection of gadolinium. They also tend to exhibit hyperostosis and calcifications which can be seen on either CT or MRI imaging. Additionally, the presence of a dural extension (also known as a dural tail) is helpful in distinguishing a meningioma from fibrous dysplasia.
The cornerstones of therapy for sphenoid wing meningioma involve observation, surgery, radiation therapy and chemotherapy.
Meningioma resection has long been considered the primary and definitive treatment for meningioma.8 Benefits to this approach include: Immediate removal of the lesion, rapid reduction of an intracranial mass effect, and the possibility to perform a precise pathological diagnosis. Surgery is typically performed using multi- stage procedures leveraging the benefits of different approaches (e.g. endoscopic endonasal surgery for anterior skull base lesions). This technique may minimize the morbidity associated with resection of the entire tumor in one operation.  Rates of gross total resection are approximately 50%. Surgical complications range from 1-18%. The 5 year recurrence free survival for WHO Grade I meningiomas is 88%.
Radiation is widely used in the management of sphenoid wing meningiomas. In the past, radiation therapy was reserved for malignant meninigomas or for recurrences. Improvement in radiation therapy technology has altered this paradigm. Treatment decisions are individualized and multimodal using both surgery and radiation for patients with symptomatic tumors. The various radiation therapy options for sphenoid wing meningiomas include: stereotactic radiosurgery, fractionated stereotactic radiotherapy (FSRT), intensity modulated radiotherapy (IMRT), and particle radiotherapy (also known as “Proton Beam”). In stereotactic radiosurgery, all of the radiation is pulsed at the tumor in one fraction while in FSRT and IMRT the dose is given in multiple fractions over time. The main difference between FSRT and IMRT is that IMRT can accommodate more complex shapes and larger tumors because it improves the ability of the radiation to conform to the tumor edge and minimize damage to important normal structures. Clinically, radiosurgery is a safe alternative to skull-base meningioma resection in patients who are not good surgical candidates; however, limitations exist for tumors in close proximity to critical and radiosensitive structures. FSRT and IMRT are generally used when the tumor is around radiosensitive structures such as the optic nerve or chiasm. For radiation therapy as a whole, local control rates of 92-100% have been reported. Rates of permanent neurological deficits range from 1.6% to 9.8%. After radiation therapy, tumor volume decreases by 33% at 2 years and 36% at 3 years.
Chemotherapy has also been used in the treatment of meningiomas that are progressive, recurrent or inoperable. Many agents have been tried including typical cytotoxic agents and mifepristone. In general, chemotherapy does not play a significant role in the management of meningioma as significant systemic toxicity is typically encountered with modest or no tumor regression seen. Combination chemotherapy with hydroxyurea is currently being evaluated. In vitro studies using targeted molecular therapies against PDGF (Platelet derived growth factor), VEGF (vascular endothelial growth factor), EGF (epidermal growth factor), and MAPK (MAP Kinase) appear promising for recurrent meningioma.
All of the treatment modalities can play a role in the management of sphenoid wing meningioma. In a review article published by Coombs, et al, they suggested a relative general standard for treating skull base meningiomas. Figure 6 is a suggested decision tree for the treatment of skull base meningiomas. The flow chart describes consideration of surgery and/or radiotherapy in the presence of symptoms, tissue compression, exophthalmos or cavernous sinus infiltration. In the absence of symptoms or signs, observation may be appropriate.
Overall, malignant potential is low for skull base meningiomas (including sphenoid wing menigomas). In a large retrospective study of 1663 patients who were operated on for menigioma, 90% were benign (WHO Grade I) tumors while only 10% were atypical or anaplastic variants (WHO Grade II or III). The major risk factors for higher WHO grade were non skull base location (OR 1.7), and age >= 65 years (OR 1.5). Male gender also conferred a 2x risk of higher WHO grade. Recurrence free survival in WHO Grade I meningioma with surgery, radiotherapy or combined treatment is nearly 90%. Morbidity varies after therapy with the incidence of permanent neurological deficits ranging from 1.6-9.8%.Morbidity from the tumor and therapeutic interventions depends on the location of the tumor and its proximity to vital neurological and ocular structures
- American Academy of Ophthalmology. Oculoplastics/Orbit: Sphenoid wing meningioma Practicing Ophthalmologists Learning System, 2017 - 2019 San Francisco: American Academy of Ophthalmology, 2017.
- Basic Clinical Science Series. Orbit, Eyelids, and Lacrimal System. American Academy of Ophthalmology. 2011-2012
- Fathi, et al. Meningioma... Curr Neurol Neurosci Rep. 2013 Apr;13(4):337. doi: 10.1007/s11910-013-0337-4.
- http://emedicine.medscape.com/article/1156552-overview#a0199 (Accessed 10/2013)
- http://emedicine.medscape.com/article/1156552-overview#a0199 (Accessed 10/2013)
- Louis, DN, et al. The 2007 WHO classification of tumors of the central nervous system. Acta Neuropathol. 2007 Aug; 114(2):97-109. Epub 2007 Jul 6.
- Wrobel, G, et al. Microarray-based gene expression profiling of benign, atypical and anaplastic meningiomas identifies novel genes associated with meningioma progression. International Journal of Cancer. Volume 114, Issue 2, pages 249–256, 20 March 2005
- Cornelius, et al. Malignant potential of skull base versus non-skull base meningiomas: clinical series of 1,663 cases. Acta Neurochir (Wien). 2013 Mar;155(3):407-13. doi: 10.1007/s00701-012-1611-y. Epub 2013 Jan 15
- Sherman, et al. Chemotherapy: what is its role in meningioma? Expert Rev. Neurother. 12(10), 1189–1196 (2012)
- Oostra, et al. Extended endoscopic endonasal skull base surgery: from the sella to the anterior and posterior cranial fossa. ANZ J Surg. 2012 Mar;82(3):122-30. doi: 10.1111/j.1445-2197.2011.05971.x. Epub 2012 Jan 17.
- Kotomotar, et al. Endoscopic endonasal versus open transcranial resection of anterior midline skull base meningiomas. World Neurosurg. 2012 May-Jun; 77(5-6):713-24. Epub 2011 Nov 7.
- Di Maio, et al. Evolution and future of skull base surgery: the paradigm of skull base meningiomas. World Neurosurg. 2012 Sep-Oct; 78(3-4):260-75. Epub 2011 Nov 7.
- Pechivanis, et al. Evidence level in the treatment of meningioma with focus on the comparison between surgery versus radiotherapy. A review. J Neurosurg Sci. 2011 Dec; 55(4):319-28.
- Combs, et al. State-of-the-art treatment alternatives for base of skull meningiomas: complementing and controversial indications for neurosurgery, stereotactic and robotic based radiosurgery or modern fractionated radiation techniques. Radiation Oncology 2012, 7:226