Long-term Results Of Gamma Knife Surgery For Optic Nerve Sheath Meningioma

Keywords: gamma knife, optic nerve, vision, meningioma, outcome

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       Optic nerve sheath tumors pose real challenges in order to save vision.
     To assess the long-term results of Gamma Knife surgery (GKS) in patients with primary optic nerve sheath meningioma (ONSM).
     Thirty patients with primary ONSM were treated with GKS between 1995 and 2003.
     Prior resection had been performed in 9 patients, and GKS was performed as the sole treatment option in 21 patients. Prescription peripheral dose varied from 10 to 17 Gy (mean 13.3 Gy); the corresponding central dose was 22 to 34Gy. The mean volume of the tumor at GKS was 3.6 cm3 (range, 1.4 to 9.7 cm3). An average of 8 isocenters (range, 5 to 14) was used for treating these lesions.
     With a median follow-up of 61 months, visual acuity improved in 11 patients, remained stable in 13 patients (including 4 patients who were completely blind before GKS) and deteriorated in 6 cases. Follow-up images were available in all patients, showing tumor regression in 20 and stable in 8. Only 2 cases showed persistent radiographic evidence of progression. Except for reversible conjunctival edema in 4 cases, no other serious acute side effect was observed.
     This was a retrospective study.
     Gamma knife radiosurgery is an effective treatment for primary ONSM.
     It provides long-term tumor control and visual preservation with low-toxic treatment modality. It adds substantial evidence that GKS may definitely become a standard treatment approach in selected cases of ONSM.


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