• Simon Diaz, Daniele Starnoni, Constantin Tuleasca, Vincent Dunet, David Peters, Mahmoud Messerer, Marc Levivier, and Roy Thomas Daniel.
• Department of Neurosurgery, University Hospital of Lausanne and Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
• Neurosurgery. 2023 Jun 1; 92 (6): 120812151208-1215.

BackgroundStereotactic radiosurgery (SRS) is an effective adjuvant therapy for residual tumor after subtotal resection of parasellar meningiomas. Fat graft placement between the optic nerve/chiasm and residual tumor (optic neuropexy [OPN]) allows for safe SRS therapy.ObjectiveTo evaluate the radiological temporal profile of the fat graft after OPN, immediately after surgery and at 3, 6, and 12 months intervals, to elucidate the optimal time point of adjuvant SRS.MethodsA single-center, retrospective, cohort study of 23 patients after surgery for parasellar meningioma was conducted. Fat graft volume and MRI signal ratios were calculated. SRS dosimetric parameters (tumor/optic nerve) were measured at the time of SRS and compared with a hypothetical dosimetric plan based on an early postoperative MRI.ResultsOf 23 patients, 6 (26%) had gross total resection and 17 (74%) had subtotal resection. Fat grafts showed a progressive loss of volume and signal ratio over time. Radiosurgery was performed in 14 (82.3%; 8 hypofractionated radiosurgery and 6 single fraction). At 3 months, there is a loss of 46% of the fat volume and degradation of its tissue intensity, decreasing differentiation from tumor and nerve. The hypothetical treatment plan (performed on an early postoperative MRI) showed that single-fraction SRS would have been possible in 6 of the 8 hypofractionated cases.ConclusionOPN is a technique that can be safely performed after resection of parasellar meningiomas. Because of the reduction of the fat volume and tissue differentiation between fat and tumor/nerves, adjuvant radiosurgery is better performed within the first 3 months after surgery.Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Congress of Neurological Surgeons.

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