Journal of Neuro-Ophthalmology, June 1998, Volume 18, Issue 2

Preservation of Residual Vision 2 Years After Stereotactic Radiosurgery for a Presumed Optic Nerve Sheath Meningioma

We performed stereotactic radiosurgery on a patient with a presumed optic nerve sheath meningioma with a progressive optic neuropathy and an intact peripheral visual field. The patient's visual acuity and visual field have remained stable for 2 years following treatment, and the appearance of the tumor has not changed by neuroimaging. We believe that stereotactic radiosurgery is a viable option for treating optic nerve sheath meningioma.

Journal of Nemo- Ophthalmology 18( 2): 117- 120, 1998. © 1998 Lippincolt- Ravcn Publishers, Philadelphia Preservation of Residual Vision 2 Years After Stereotactic Radiosurgery for a Presumed Optic Nerve Sheath Meningioma David F. Klink, D. O., Neil R. Miller, M. D., and Jeffrey Williams, M. D. We performed stereotactic radiosurgery on a patient with a presumed optic nerve sheath meningioma with a progressive optic neuropathy and an intact peripheral visual field. The pa­tient's visual acuity and visual field have remained stable for 2 years following treatment, and the appearance of the tumor has not changed by neuroimaging. We believe that stereotactic ra­diosurgery is a viable option for treating optic nerve sheath meningioma. Key Words: Optic nerve sheath meningioma- Meningioma- Radiation- Stereotactic radiosurgery. Therapy for optic nerve sheath meningioma ( ONSM) is controversial. Surgical resection can rarely be accom­plished without sacrificing the remaining vision in the affected eye. Hormonal therapy holds promise for the future but is still investigational. Conventional radiation therapy has been performed in patients with ONSM, and some investigators report stabilization and even im­provement in visual function after radiation ( 1- 9). Lee et. al. ( 10) recently reported improvement in visual func­tion in a patient with a presumed ONSM who was treated with three- dimensional conformal radiation therapy. We describe a patient who has maintained pretreatment vi­sual function, including a full peripheral visual field, for 2 years after stereotactic radiosurgery for a presumed ONSM. The patient, a 40- year- old woman, who had complaint of 6 months' intermittent blurred vision in the right eye, first sought medical care at another institution in Febru­ary 1989. Visual acuity was 20/ 25 + 2 OD and 20/ 20 OS. Color vision test results were normal except that the patient read the color plates more slowly with the right eye. Automated perimetry of the right eye showed an enlarged blind spot with generalized depression. Fundus examination showed a swollen right optic disc ( Fig. 1). Magnetic resonance imaging revealed a 1.6- cm mass sur- Manuscript received June 24, 1997; accepted November 18, 1997. From the Department of Opthalmology, National Naval Medical Center ( D. F. K.), Bethesda, Maryland, and Departments of Opthalmol­ogy, Neurology, and Neurosurgery ( N. R. M.). and Departments of Neurosurgery, Stereotactic Radiosurgery, and Oncology ( J. W.), Johns Hopkins Hospital, Baltimore, Maryland. Address correspondence to Neil R. Miller, M. D., Maumenee B- 109, Wilmer Eye Institute, Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287- 9204, U. S. A. FIG 1. Right optic disc at the time of initial examination shows moderate disc swelling. rounding the optic nerve in the right posterior orbit. This was thought to be most consistent with an ONSM. The patient was observed for the next 3 years, during which time the vision in the right eye declined to 20/ 200. She was first examined by one of us ( N. R. M.) in Oc­tober 1992 after relocating to our area. Visual acuity was 20/ 200 OD and 20/ 15 OS. Color test results were 5.5/ 10 OD and 9.5/ 10 OS using Hardy- Rand- Rittler pseudoiso-chromatic plates. There was a right relative afferent pu­pillary defect. Visual field testing of the right eye showed a dense central scotoma with an intact peripheral field. The right optic disc was swollen, and the fundus exhib­ited choroidal folds. The left eye was normal. During the next year, color vision in the right eye declined to 1/ 10, and automated perimetry showed further decline in mean deviation and foveal sensitivity. Magnetic resonance im­aging showed no change in the size or shape of the lesion, and the patient declined treatment. By October 1994, visual acuity had declined to 20/ 300 OD. The patient could detect only gross color with the right eye. The right optic disc remained swollen, and an optociliary shunt vessel had developed at 2 o'clock. The mean deviation on automated perimetry had decreased to - 20.88 DB from - 10.98 DB 18 months earlier, and foveal sensitivity had declined to 6 DB from 22 DB 18 months earlier ( Fig. 2A). The peripheral field was still intact ( Fig. 2B). Magnetic resonance imaging showed 117 118 D. F. KLINKETAL. slight posterior extension of the mass along the optic nerve ( Fig. 3). Radiation therapy consultation was ob­tained, and the patient's case was presented at a weekly neurosurgery conference. The consensus was that sur­gery would not cure the patient, would almost certainly sacrifice all remaining vision in the right eye, and would carry a significant risk of permanent ptosis and ophthal-moparesis. Radiation treatment was recommended. Based on the patient's clinical course and neuroimaging studies, it was thought that she could be treated without a tissue diagnosis. Stereotactic radiosurgery would allow the delivery of a larger radiation dose to the tumor, mini­mize the radiation dose to surrounding tissues, and ac­complish treatment in 6 sessions versus 30 for conven­tional radiotherapy. However, there was concern that the higher daily fraction might place the optic nerve at greater risk of radiation necrosis. After discussing all options, the patient chose to be treated with stereotactic radiosurgery. The patient was treated with fractionated stereotactic radiosurgery from January 18- 25, 1995. She first had sequential fitting of the relocatable thermoplastic mask and a Brown- Roberts- Wells stereotactic frame. After placement of the frame, a contrast- enhanced cranial com­puted tomographic ( CT) scan defined the Brown- Roberts- Wells fiducials, tumor, optic nerves, and orbits. The border of the meningioma was outlined, and the isocenter was placed using the optimum collimator di­ameter ( 21 mm). This treatment plan spared the unaf­fected left optic nerve, the optic chiasm, and the lens. Stereotactic radiosurgery was delivered using a modi­fied 10 MeV linear accelerator by five arcs: two trans­verse ( each 120°), two oblique ( each 100°), and 1 sagittal ( 100°). For prescription of the dose ( Gy: 1 Gray = 100 rad), we used the biologically effective dose ( BED) for­malism ( 10). A regimen, the intensity of which exceeded conventional external- beam radiotherapy ( 60 Gy in 30 FIG. 2. Preoperative perimetry. A: Automated static perimetry s was - 20.88 DB and the toveal sensitivity was 6 DB. B: Kinetic peripheral field. fractions: BED = 100) was chosen for fractionated ste­reotactic radiotherapy ( 36 Gy in 6 fractions: BED = 108). Thus, spatial localization of close and effective total dose exceeded those possible with conventional radio­therapy. The patient experienced periorbital edema and head­ache for several months after radiation- thought to be related to lymphatic obstruction. Pain was controlled with nonsteroidal antiinflammatory medication. The headache and edema resolved within 9 months after the radiosurgery. Three months after treatment, visual acuity was 20/ 200 OD. Color vision was unchanged. Disc swelling had resolved, and the right optic disc was pale. Mean devia­tion on automated static perimetry had improved to - 13.06 DB, and fovea! sensitivity had increased to 18 DB ( Fig. 4A). Kinetic perimetry showed a full peripheral field in the right eye ( Fig. 4B). The left eye remained normal. Magnetic resonance imaging findings remained unchanged. Magnetic resonance imaging was last performed in March 1997 and showed no change in the size or shape of the tumor. Findings in clinical examination remained unchanged on the most recent follow- up in April 1997. Most notably, kinetic perimetry showed no deterioration of the peripheral visual field of the right eye. The patient maintained full ocular motility and exhibited no ptosis. Of 12 cases reported in the literature of ONSM treated with conventional radiotherapy, visual acuity improved in 75%, remained stable in 8%, and declined in 17% ( 1,4- 6). The results in our patient are consistent with those reported in conventional radiotherapy of ONSM. Comparison with three- dimensional conformal radiation therapy is difficult; the results of treatment have been reported in only one patient by Lee et al. ( 10). Fractionation of dose may reduce the late effect of radiation on the affected optic nerve ( 11). Parsons J20 105 90 75 60 generalized depression with a central scotoma. The mean deviation letry shows a dense central scotoma to the 114 isopter with an intact ./ Ncum- Ophlhiilniol. Veil. IX, NIK 2, I99H i H IH HtU1E| i If i 11 n ar- a. FIG. 3. A: Axial T1- weighted magnetic resonance image after administration of gadolinium- diethylenetriamine penta- acetic acid ( DPTA) contrast material shows a mass in the right posterior orbit deflecting the optic nerve. B: Axial T1- weighted magnetic resonance image after administration of gadolinium- DPTA con­trast material shows posterior extension of the mass along the optic nerve relative to previous neuroimaging studies. C: Coronal T2- weighted magnetic resonance image shows a mass in the right posterior orbit partially surrounding the optic nerve. 12Q MS 75 60 '' * ' ' i % v ^ t ^ ^ < J-! AJS?:*: 5 m mmm >*:%? FIG. 4. Postoperative perimetry. A: Automated static perimetry shows improvement with a mean deviation of - 13.06 DB and a foveai sensitivity of 18 DB. B: Kinetic perimetry shows a dense central scotoma to the 14 isopter with an intact peripheral field. 120 D. F. KLINKET AL. et al. ( 12) estimated the 15- year actuarial risk of devel­oping radiation- induced injury to the optic nerve to be 11% to 47% in patients treated with 60 Gy or more of fractionated external- beam radiation, with lower rates seen in those receiving smaller fraction sizes. They also recommended using reduced- field techniques to limit the volume of tissue exposed to high- dose irradiation. Al­though the effects of stereotactic radiosurgery on cranial nerves are not fully known, the precise localization of dose to the tumor may spare the unaffected optic nerve and provide additional safety. Leber et al. ( 13) reported on 29 patients treated with gamma knife radiosurgery for benign skull base tumors. No patient exhibited injury to cranial nerves III, IV, V, or VI with exposure to radiation doses of as much as 30 Gy, although 31 % of patients with pre- existing optic neuropathy had their disorders worsen after exposure to radiation doses of 6 to 16.6 Gy. In our opinion, stereotactic radiosurgery is a viable option for treating ONSM. This modality reduces the radiation dose to surrounding structures while increasing the effective total dose that can be delivered to the tumor. It may preserve remaining vision and may ultimately reduce the complications often associated with conven­tional radiation therapy. REFERENCES I. Smith JL, Vuksanovic MM, Yates BM, Bienfang DC. Radiation therapy for primary optic nerve meningiomas. J Clin Neuro-ophthalmol 1981; 1: 85- 99. 2. Alper MG. Management of primary optic nerve meningiomas. J Clin Neuro- ophthalmol 1981; 1: 101- 7. 3. Kuppersmith MJ, Warren FA, Newall J, Ranshoff J. Irradiation of meningiomas of the intracranial anterior visual pathway. 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