Visual Outcome After Single-session Gamma Knife Radiosurgery For Perioptic Meningiomas

Amr El-Shehaby, MD1, Wael Reda, MD1, Khaled Abdel Karim2

1Gamma Knife Center Cairo, Nasser Institute 2Gamma Knife Center, Nasser Institute, Cairo, Egypt

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

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       Perioptic meningiomas present a challenge for single-session stereotactic radiosurgery due to the low radiation tolerance of the anterior visual pathway. Fractionated radiation therapy and multisession stereotactic radiosurgery are sometimes proposed to reduce radiation toxicity to the visual pathway, when treating these tumors.
     This retrospective study aims at assessing the visual outcome after single-session gamma knife radiosurgery (SSGKS) for meningiomas in direct contact with the anterior visual pathway.
     Between August 2001 and December 2006 123 consecutive patients with skull base meningiomas were treated by single-session GKS. Seventy-three patients had meningiomas that were either in direct contact or displacing the anterior visual apparatus. The mean age was 50 years (21-80 years). Twenty patients had had previous surgery and one patient was previously treated by conventional fractionated radiotherapy.
     Between August 2001 and December 2006 123 consecutive patients with skull base meningiomas were treated by single-session GKS.The mean follow up period was 34 months (12-72 months). The tumor volumes ranged from 0.95-34.2 cc (median 10.1 cc) with 39 patients having tumor volumes = 10 cc. The marginal dose was between 6 and 12 Gy (mean 11.3 Gy) and the maximum dose to visual pathway was from 2 to 13.7 Gy (mean 9.3 Gy). Formal visual testing and clinical examination was performed before treatment and at follow up intervals beginning at 6 months.
     The visual field improved in 30 patients (42%), remained stable in 39 (53%) and worsened in 4 (5%). Ocular nerve palsy improved in 10 (63%) out of the 16 patients with pre-treatment palsy. Tumor volume after SSGKS was stable in 46 patients (60%), decreased in 26 (36%) and increased in 3 (4%). Out of the 30 patient with visual field improvement, 15 patients (50%) had no radiologically-proven tumor shrinkage.
     This is a retrospective study.
     Tumor shrinkage is not a pre-requisite for functional improvement.
      Single-session gamma knife radiosurgery may be a safe and effective treatment for tumors in contact with the optic apparatus, with the possibility of visual and ocular nerve function improvement.


Project Roles:

A. El-Shehaby (), W. Reda (), K. Karim ()