Cavernous sinus meningioma – immediate postoperative radiosurgery for residual tumor after repeat resection

SKULL BASE REGION	Right cavernous sinus
HISTOPATHOLOGY	Meningioma, WHO Grade 1
PRIOR SURGICAL RESECTION	Yes
PERTINENT LABORATORY FINDINGS	N/A

Case description

The patient is a 76-year-old male with a known history of a large, cavernous sinus meningioma (CSM) status post first subtotal microsurgical resection around 21 years prior to presentation, with a residual intracavernous component. The tumor recurred, necessitating a second microsurgical resection at another institution, where the histopathologic diagnosis remained WHO grade 1 meningioma. We recommended stereotactic radiosurgery (SRS) to the residual tumor ( Figure 5.24.1 ) using Gamma Knife, and the patient agreed to this intervention ( Figure 5.24.2 ).

Radiosurgery Machine	Gamma Knife – Perfexion
Radiosurgery Dose (Gy)	12, at the 50% isodose line
Biologically Effective Dose (Gy)	73.06 Gy
Number of Fractions	1

Critical Structure	Dose Tolerance
Optic pathways	The maximal dose to the optic pathways in patients without prior radiotherapy was classically 8 Gy Recently, the dose limit has been extended to 10 or even 12 Gy
Cavernous internal carotid artery (ICA)	New or progressive ICA stenosis/occlusion is considered, by some authors, common after stereotactic radiosurgery for cavernous sinus meningiomas (CSMs) ICA encasement or constriction increases the risk of ICA stenosis/occlusion, but the risk of ischemic complications is very low
Cavernous sinus neural contents	Cranial nerves within the cavernous sinus are more radioresistant compared to the optic nerve; however, they are considered more sensitive in case of prior irradiation, during which a maximal dose of 8 Gy to the optic apparatus is a safe choice