Preliminary results after multisession gamma knife radiosurgery for perioptic meningiomas.

Keywords: meningioma, outcome, gamma knife, fractionated stereotactic radiotherapy, vision

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     Parasellar meningiomas create challenges for vision and neurologic function.
     Our purpose was to evaluate the effectiveness and safety of a Gamma Knife treatment in three consecutive days (multisession) in patients with parasellar meningioma in close contact to the optic nerve and chiasm.
     Between January 2006 and September 2010 49 patients (41 females, 8 males, mean age 57 years) underwent multisession gamma knife treatment at San Raffaele Hospital for a meningioma in close contact to the optic nerve and chiasm. Five patients have been treated for optic nerve meningioma, 44 for a parasellar meningioma.
     Preoperative decreased visual acuity or visual fields defect was found in 28 patients. Gamma Knife radiosurgery was delivered in three sessions with a mean prescription isodose of 6.8 Gy per session (range 6.5-7 Gy) and a mean total prescription isodose of 20.7 Gy (range 19.5-21 Gy). Mean tumor volume was 8.8 ml (median 7.6, range 0.33-34.2). Maximum dose to the optic apparatus was always below 7 Gy for each session (mean 5 Gy).
     Median follow-up was 29.5 months (range 6-57). Overall tumor control rate was 100%. Tumor volumetric reduction was observed in 33 patients (67%), whereas in 16 patients (33%) no volumetric change was recorded. No patient experienced worsening of visual function, in 5 patients (10%) visual acuity improved after treatment; visual field improvement occurred in 4 patients (8%). Cranial nerve function improvement was recorded in 2 patients (4%); one patient experienced VI cranial nerve paresis (2%).
     This was a retrospective series.
     This preliminary experience suggests that multisession radiosurgery with Gamma Knife can be a safe and effective treatment for tumors immediately adjacent to segments of the optic apparatus.
     These findings should be validated by other centers.


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