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as long as possible. In 1977, we were able to remove a meningioma that was eccentric to the optic nerve and restored vision in a woman from 20=200 to 20=20. Her visual field recovered nearly completely as well. She has now been followed for more than 20 years and the meningioma has recurred in the medial orbit, but does not compress the optic nerve at this time. She will need removal of the tumor through an anterior medial orbitotomy if afferent dysfunction recurs.
In contrast, most of the primary optic nerve sheath meningiomas are located in the intradural space or as a combination of intraand extradural components. On MRI, they have a characteristic appearance with the nerve surrounded by gadolinium-enhanced tumor (the tram track sign). On CT, the nerve appears thickened and may be calcified. These are more difficult to manage, and although biopsy of the extradural component is usually safe, biopsy or attempted removal of the intradural component leads to marked decrease in vision, probably due to the interruption of the blood supply to the optic nerve. We also have learned that a neurosurgical approach that allows successful removal of most of the intradural portion of the meningioma results in further postoperative orbital progression. The clinical course, in combination with neuro-imaging, allows us to diagnosis most intradural primary optic nerve sheath meningiomas with confidence, when agreement is reached between the ophthalmologist, neurosurgeon, and neuro-radiologist regarding the nature of the tumor. Therefore, we developed a strategy of treating these patients with progressive vision loss before the loss was profound: radiotherapy (5000–5500 rad) is directed from a lateral portal with global protection without a biopsy, or with biopsy of the extradural portion only.
THERAPEUTIC RECOMMENDATIONS
1.If visual acuity is between 20=20 and 20=30, OBSERVE.
2.If visual acuity is 20=30 or worse with progressive visual fields, RADIATION.
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3.If vision is no light perception, SURGICAL EXCISION.
Based on 30 years of experience, we have found that patients with progressive vision loss due to presumed or biopsied primary optic nerve sheath meningiomas can maintain or improve their usual functional vision following radiotherapy.
In 1988, we reported a series of 39 optic nerve sheath meningiomas: 18 were observed, 6 radiated, 10 totally removed, and 5 had partial excision or biopsy followed by radiation therapy. Only the six who were radiated, retained or improved vision in the affected eye for 3–6 years (Fig. 1). Recently, we have completed a multicenter study that confirms that radiotherapy preserves long-term visual function in patients with primary optic nerve sheath meningiomas. In the study, we compared long-term visual outcome in patients with primary optic nerve sheath meningiomas managed by traditional treatments. The group evaluated consisted of 55 women and 9 men. We used a decimal visual acuity scale limiting the investigation to assessment of visual acuity. In addition, we used a nonparametric testing plan and statistical analysis to determine the effect of various management methods. The treatment methods analyzed were observation (13 patients), surgery only (12), radiation only after radiologic diagnosis (18 patients),
Figure 1 1988 Optic Nerve Sheath Meningioma Study.
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and surgery consisting of a biopsy followed by radiation (16 patients). The patients treated with radiation only clearly had better long-term visual outcomes than patients who were simply observed. As suspected, patients with surgical removal of the optic nerve suffered profound visual loss and patients who underwent surgery followed by radiation did not have good visual preservation (Fig. 2). The radiation dosage was 4000– 5500 rad with the majority receiving between 5000 and 5500 rad. The radiation often improved vision with long-term maintenance of the improvement.
Our conclusion is that patients with optic nerve sheath meningiomas receiving radiation treatment only, after convincing radiologic diagnosis, demonstrated the best visual outcome during the period of follow-up. We recommend radiation for patients who have optic nerve sheath meningiomas, characteristic in clinical course and neuroradiologic findings, for long-term preservation of visual function.
Radiation complications were seen in 33% of the patients and included vascular occlusion or retinopathy in four patients, persistent iritis in one, and temporal lobe atrophy in one. The patients with surgery only or radiation and surgery had significant complication rates of 66.0% and 62.5%, respectively. This also convinces us that the complications of other treatments
Figure 2 2001 Optic Nerve Sheath Meningioma Study.
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justify the management of these patients with radiation without the necessity of biopsy in characteristic cases.
Of course, children with optic nerve meningiomas are treated more aggressively with complete surgical removal in unilateral cases and radiation of at least one nerve in aggressive bilateral optic nerve cases.
SPHENOID WING MENINGIOMAS
Sphenoid wing meningiomas arise from the arachnoid adjacent to the sphenoid wing. The sphenoid wing is about 5 cm long, but the tumors are usually divided into those arising from the outer, middle, or inner wing. We manage all sphenoid wing meningiomas in a similar fashion.
Sphenoid wing meningiomas can grow quite large intracranially. They have a propensity to invade the bone causing significant boney thickening, which results in proptosis and fullness of the temporalis fossa, often prior to functional loss of vision or extraocular movement. Of course, the more medial the tumor, the earlier effect on visual function and the less tendency for significant proptosis. Outer sphenoid wing meningiomas often have a significant boney component and are often confused with fibrous dysplasia, although they characteristically occur in an older age group. The soft-tissue components of these meningiomas tend to invade the superior orbital fissure, the cavernous sinus, and the lateral superior orbit. The outer wing meningiomas, if they grow large intracranially, can cause dementia or personality changes as an initial clinical sign. Occasionally, they are quite vascular and can hemorrhage into themselves with catastrophic neurologic sequelae. The orbital extension is typically extraconal and superolateral between the lateral and=or superior recti muscles and the adjacent orbital wall. Occasionally, they invade the intraconal space, making them more difficult to remove from the orbit.
These meningiomas are usually easily diagnosed with MRI or CT. Both techniques are recommended as MRI better shows the soft-tissue component, especially with gadolinium, and CT better shows better the extent of boney involvement.
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The treatment of the sphenoid meningiomas continues to be surgical resection as complete as possible. Unfortunately, subtotal excision is common due to the proximity to and infiltration of the orbit and cavernous sinus. In the late 1970s, we realized that we were frequently operating on meningiomas which had recurred, so we sought a therapy to prevent recurrence following surgery. It was found that external beam radiation can effectively delay recurrence following subtotal removal. It is often impossible to totally remove the sphenoid wing meningioma, particularly when it invades the crevices of the superior orbital fissure, cavernous sinus, or the orbit. In addition, radiation therapy can preserve the remaining visual function, as it does with primary optic nerve sheath meningiomas. The dose is 5000–5500 rad of external beam radiation from a lateral port. In 1996, we previously reported the effectiveness of radiation therapy following subtotal excision of sphenoid wing meningiomas, thus preventing recurrences (Figs. 3 and 4). We have found that radiation therapy following subtotal removal of these tumors delays recurrences in both primary and recurrent tumors. Recently, after a review of our sphenoid wing meningiomas with a longer follow-up period, we again found that recurrence is prevented if radiation therapy is delivered approximately 2 months following
Figure 3 Primary sphenoid wing meningiomas, 1996.
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Figure 4 Recurrent sphenoid wing meningiomas, 1996.
the initial tumor excision, and appears to delay recurrence in already recurrent tumors (Figs. 5 and 6).
In our study, 65 primary sphenoid meningiomas were evaluated. No patients receiving radiation 2 months after their initial excision recurred. In contrast, 28 patients not
Figure 5 Primary sphenoid wing meningiomas, 2002.
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Figure 6 Recurrent sphenoid wing meningiomas, 2002.
receiving radiation recurred (14 were stable). For already recurrent tumors, 70% of patients who did not receive radiation recurred. This contrasts with 27% recurrence rate in the recurrent tumors who received postoperative radiotherapy.
Other therapies for large intracranial meningiomas have been tried. Hormonal therapy is of limited effectiveness. Hydroxyurea therapy is somewhat useful in inoperable or aggressive intracranial meningiomas, but not of value in sphenoid wing or optic nerve sheath meningiomas. Gene therapy is promising in meningiomas but because of their indolent course and other priorities for gene therapy, it will be some time before these may be of practical use.
Finally, studies on the social and functional aspect of patients treated surgically with or without radiotherapy show that the majority of patients undergoing treatment for intracranial meningioma remain functional, productive, and capable of independent living. Timely radiation in optic nerve sheath meningiomas and surgical debulking augmented with radiation in sphenoid wing meningiomas maximizes patients’ long-term visual and neurologic functions.
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REFERENCES
Optic Nerve Sheath Meningiomas
1.Alper MG. Management of primary optic nerve sheath meningiomas. J Clin Neuro Ophthalmol 1981; 1(2):101–117.
2.Dutton JJ. Optic nerve sheath meningiomas. Survey Ophthalmol 1992; 37(3):167–183.
3.Jakobiec FA, Depot MJ, Kennerdell JS, Shults WT, Anderson RL, Alper ME, Citrin CM, Housepian EM, Trokel SL. Combined clinical and computed tomographic diagnosis of orbital glioma and meningioma. Ophthalmology 1984; 91(2):137–155.
4.Kennerdell JS, Maroon JC, Garrity J, Warren F. The management of optic nerve sheath meningiomas. Am J Ophthalmol 1988; 106:450–457.
5.Smith JL, Vuksanovic MM, Yates BM, Bienfang DC. Radiation therapy for primary optic nerve meningiomas. J Clin Neuro Ophthalmol 1981; 1(2):85–99.
6.Sibony PA, Kennerdell JS, Slamovits TI, Lessell S, Krauss HR. Intrapapillary retractile bodies in optic nerve sheath meningioma. Arch Ophthalmol 1985; 103:383–385.
Sphenoid Wing Meningiomas
1.Al-Mefty O, Kersh JE, Routh A, Smith RR. The long-term side effects of radiation therapy for benign brain tumors in adults. J Neurosurg 1990; 73:502–512.
2.Cockerham KP, Kennerdell JS, Maroon JC. Tumors of the meninges and related tissues: meningiomas and sarcomas. In: Miller NR, Newman NJ, eds. Walsh and Hoyt Textbook of Neuro-Ophthalmology. Vol. 2. 5th ed. Baltimore: Williams & Wilkins, 1997:2017–2082.
3.Goldsmith BJ, Wara WM, Wilson CB, Larson DA. Postoperative irradiation for subtotally resected meningiomas. A retrospective analysis of 140 patients treated from 1967 to 1990. J Neurosurg 1994; 80:195–201.
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4.Maroon JC, Kennerdell JS, Vidovich DV, Abla A, Sternau L. Recurrent spheno-orbital meningioma. J Neurosurg 1994; 80(2):202–208.
5.Newman SA. Meningiomas: a quest for the optimum therapy. J Neurosurg 1994; 80:191–194.
6.Peele KA, Kennerdell JS, Maroon JC, Kalnicki S, Kazim M, Gardner T, Malton M, Goodglick T, Rosen C. The role of postoperative radiation in the surgical management of sphenoid wing meningiomas. Ophthalmology 1996; 103(11):1761–1766.
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Gliomas of the Anterior Visual
Pathway
JONATHAN J. DUTTON
University of North Carolina,
Chapel Hill, North Carolina, U.S.A.
Intrinsic tumors of the optic nerve include optic gliomas and optic sheath meningiomas. Together, they account for less than 4% of all orbital tumors, with optic gliomas representing approximately 65% and meningioma 35% of this group (1). Despite the large literature that has accumulated concerning anterior visual pathway gliomas, there is still considerable controversy regarding their natural history and appropriate management (2).
In 1816, Antonio Scarpa gave the first clinical description of optic nerve tumors. His patients clearly had several different diseases, including extraocular extension of retinoblastoma and adult optic sheath meningioma. However, some were children who appear to have had gliomas of the optic
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