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Show journal of Neuro- Ophthalmology 16( 4): 247- 251, 1996. © 1996 Lippincott- Raven Publishers, Philadelphia Improvement in Visual Function in an Eye with a Presumed Optic Nerve Sheath Meningioma after Treatment with Three- Dimensional Conformal Radiation Therapy Andrew G. Lee, M. D., Shiao Y. Woo, M. D., Neil R. Miller, M. D., Avinoam B. Safran, M. D., Walter H. Grant, Ph. D., and E. Brian Butler, M. D. The t r e a t m e n t of optic nerve sheath meningiomas ( ONSM) is controversial. Radiation therapy has been used with some success in patients with progressive visual loss. We report a case of visual improvement in a patient with an optic nerve sheath meningioma and progressive visual field loss, treated with conformal radiotherapy. Key Words: Optic nerve sheath meningioma- Radiation- Meningioma. Manuscript received August 18, 1995; accepted October 20, 1995. From the Neuro- Ophthalmology Unit, Cullen Eye Institute, Departments of Ophthalmology, Neurology, and Neurosurgery ( A. G. L.) and Department of Radiation Therapy ( S. Y. W., W. H. G., E. B. B.), Baylor College of Medicine, Houston, Texas, U. S. A.; Neuro- Ophthalmology Unit, Departments of Ophthalmology, Neurology, and Neurosurgery, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore, Maryland, U. S. A. ( N. R. M.); and Neuro- ophthalmology Unit, Hospital Cantonal Universitaire, Geneva, Switzerland ( A. B. S.). Address correspondence and reprint requests to Dr. Andrew G. Lee, 6501 Fannin Street, NC- 200, Baylor College of Medicine, Houston, Texas 77030, U. S. A. Primary optic nerve sheath meningiomas ( ONSM) are uncommon tumors and account for only 1- 2% of all meningiomas. Dutton ( 1) reviewed the literature on these tumors in 1992 and reported a mean age at presentation of 40.8 years ( age range 2.5- 78 years), a female predominance ( 61%), and a unilateral tumor in 95% of cases ( 1). The clinical features of ONSM include progressive loss of visual acuity or visual field ( 96%), proptosis ( 59%), optic disc abnormalities ( 98%) such as chronic disc swelling ( 48%) or optic atrophy ( 49%), and optociliary veins ( 30%) ( 1). Computed tomographic ( CT) and magnetic resonance ( MR) scans have allowed the diagnosis of ONSM to be made in many cases without tissue biopsy ( 1- 4). Although management of these tumors is somewhat controversial, conservative treatment is usually preferred due to the characteristic slow and indolent growth pattern of ONSM and the extremely low tumor- related mortality rate. Radiation therapy has been reported with some success in a number of reports ( 1- 11). We report improvement in visual field loss in a patient with ONSM after treatment with conformal radiotherapy. CASE REPORT A 43- year- old white woman was found to have asymptomatic swelling of the left optic disc during a routine eye examination in February, 1991. Past medical, surgical, and ocular histories were unremarkable. Family history was significant for a sister with multiple cafe- au- lait spots but no other stigmata of neurofibromatosis type 1. 247 248 A. G. LEEETAL. FIG. 1. Axial T1- weighted MR image after administration of gadolinium- DTPA contrast material shows enhancement of the optic nerve sheath on the left side ( arrow). The patient was in her usual state of good health until February, 1991, when during a routine ophthalmologic examination, she was found to have optic disc swelling in the left eye. She was referred to one of us ( A. B. S.), who found normal visual acuity, color vision, visual field, and motility examinations in each eye and confirmed the left-sided optic disc swelling. CT and MR scans of the head and orbits revealed an enlarged optic nerve on the left that was thought to be consistent with an optic nerve sheath meningioma ( Fig. 1). In May, 1991, the patient was noted to have 1.5 mm of proptosis and mild persistent optic disc swelling in the left eye, but the remainder of the neuro-ophthalmologic exam was unchanged. Over the next 2 years, the patient's visual acuity remained 20/ 15 in both eyes, and serial MR scans showed no change in the size or shape of the lesion. In January, 1992, visual field testing in the left eye revealed a mild inferior defect. By June, 1993, the visual field defect was increased in size. On December 12, 1994, the patient was evaluated by one of us ( N. R. M.), at which time the neuro-ophthalmologic examination revealed a visual acuity of 20/ 15 OD and 20/ 20 OS. The patient correctly identified 15 of 15 Hardy- Rand- Rittler ( HRR) color plates with each eye. The pupils were isocoric, but the left pupil reacted less briskly to light than did the right pupil, and there was a mild left relative afferent pupillary defect. Static and kinetic testing revealed no abnormalities in the visual field of the right eye. Static perimetry of the left eye showed a mean deviation of - 11.33 db associated with an inferior altitudinal defect ( Fig. 2). Motility examination revealed minimal limitation of abduction of the left eye. The patient was orthotropic at distance and near in the primary gaze position, but developed an esotropia of 8 prism diopters in gaze to her left. Slit- lamp examination was normal in each eye. General physical examination was normal and, specifically, she had no cafe- au- lait spots or axillary freckles. Hertel exophthalmometry measured 16 mm in the right eye and 18 mm in the left eye at a base of 94 mm. Ophthalmoscopy revealed a normal right ocular fundus. In the left eye, there was mild swelling of the optic disc associated with a single optociliary retinochoroidal shunt vessel ( Fig. 3). A variety of management options, including observation, conventional radiotherapy, con-formal radiotherapy, hormone therapy, and surgery were discussed with the patient. The patient elected to undergo conformal radiation therapy using the Peacock System ( 12). This system creates optimized, three- dimensional, highly conformal dose distributions using an inverse solution that requires intensity modulated beams ( 13). The radiation is delivered using a mul-tivane collimator ( Fig. 4) that is placed in the accessory tray holder of the linear accelerator. To insure accuracy in radiation treatment delivery, the head of the patient must be immobilized during treatment sessions. This immobilization system consists of two screws attached to the vertex of the cranium, into which a removable alumi- 8 • • • » £ • St :: FIG. 2. Static perimetry on December 12, 1994 of the left eye demonstrates inferior visual field defect. / Neuro- Ophthalmol, Vol. 16, No. 4, 1996 ONSM TREATED WITH CONFORMAL RADIOTHERAPY 249 FIG. 5. Attachment of patient's head to treatment couch. FIG. 3. Optic disc photograph of the left eye shows mild disc edema and a possible optociliary shunt vessel interiorly at 6 o'clock ( arrow). num bar is attached ( Fig. 5). For CT planning and treatment, this bar is coupled to an adjustable vertical bracket attached to the head of the treatment couch ( Fig. 6). After each treatment, the bar is removed from the patient's head, leaving only the two small fixation screws on the patient's cranium. Cleaning of these screw sites is performed daily with peroxide and iodine as well as a daily dressing change. Radiation is then planned and delivered in segmental arcs, much like a standard CT scan. Phantom film dosimetry to confirm the treatment plan is carried out before the actual treatment begins. As the gantry rotates around the patient, each of 40 small " beams" defined by the collimator is turned on or off by the movement of its vane for a 0 r C © •"'" • WTTggT" ^ KTffi. i. M> ffJU c © • u M variable period of time during each 5° of arc. This permits spatial modulation of the beam intensity through temporally variable attenuation of the treatment beam. After each arc, the couch table top of the linear accelerator is indexed at a precise distance, and another arc is then delivered. The indexing is accomplished with a customized device that attaches to the side rails of the treatment couch and has digital readout in hundredths of a millimeter. Figure 7 shows the isodose distribution of radiation for this patient's tumor. The tumor receives the maximum dosage ( 5233 cGy), whereas the contralateral optic nerve and surrounding brain receive much lower dosages of radiation than the target. In our patient, the total dose of radia- FIG. 4. Multivane collimator of Peacock system. FIG. 6. Patient is positioned and aligned during treatment session. / Neuro- Ophthalmol, Vol. 16, No. 4, 1996 250 A. G. LEEETAL. 465- eQy 9014 5ZP cQ</ FIG. 7. Isodose distribution map. Maximum radiation dose ( 5233 cGy) delivered to optic nerve sheath tumor ( curved arrow). Minimal radiation delivered to contralateral optic nerve and surrounding brain ( straight arrow). 1 Right L » « | Axial lm$ gs 5 • • ] Optic Gfilu- T B H Brain Alain i u* ito* ii • 1 OpibNBn ™ • i fain • • • Taigflt l 3of4 | M M CSV tion delivered to the tumor was 5040 cGy given in 180 Cgy fractions over a 6- week period of time. One week after the completion of treatment, on March 7,1995, the neuro- ophthalmologic examination revealed a visual acuity of 20/ 15 OD and 20/ 15 OS. Color vision was 14 of 14 in each eye using Ishihara color plates. The optic disc swelling on the left side was unchanged. Static perimetry of the left eye showed a mean deviation of only - 2.21 db, associated with a mild inferior defect ( Fig. 8). DISCUSSION The treatment of ONSM remains controversial; however, the use of radiotherapy in patients with documented progressive visual loss has been gaining wider acceptance. Visual improvement was reported, in the literature review by Dutton ( 1), by 12 of 16 ( 75%) patients treated with conventional radiation therapy. Treatment of ONSM with conventional radiation therapy also exposes the optic chiasm and contralateral optic nerve to radiation however, resulting » • £ • « • « • • FIG. 8. Static perimetry on March 7, 1995 shows marked reduction of visual field defect interiorly. / Nemv- Ophthalmol, Vol. 16, No. 4, 1996 ONSM TREATED WITH CONFORMAL RADIOTHERAPY 251 in radiation- induced necrosis in up to 15% of patients ( 9,11). Sarkies ( 4) reported a patient with bilateral ONSM treated with conventional radiation therapy of 1325 cGy to both orbits and chiasm in whom therapy was terminated prior to completion because of progressive visual loss believed to be due to radionecrosis ( 4). Thus, more precise ra-diotherapeutic modalities are desirable when treating these histologically benign tumors. Few reports describe the use of precision radiation techniques in the treatment of optic nerve sheath meningiomas ( 8). The present report is the first report, to our knowledge, of treatment of an ONSM with three- dimensional conformal radiotherapy ( Peacock). This technique employs plan optimization by computer analysis and intensity modulation of the radiation beam during treatment to maximize delivery of radiation dose to the tumor and minimize the dose to surrounding tissues. 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