Stereotactic radiosurgery offers a high rate of tumor control and neurological preservation in patients with skull base meningiomas. After radiosurgery, better outcomes were observed for those receiving an optimal radiosurgery dose and harboring tumors located in a cerebellopontine angle, parasellar, or petroclival location.

Gamma Knife surgery offers an acceptable rate of tumor control for posterior fossa meningiomas and accomplishes this with a low incidence of neurological deficits. In patients selected for GKS, tumor progression is associated with age greater than 65 years and decreasing dose to the tumor margin. Clival- or petrous-based locations are predictive of an increased risk of new or worsening neurological deficit following GKS.

M eningioMas are the most frequently reported primary intracranial neoplasms in the US. Most of these lesions are benign (i.e., WHO Grade I) with a low tendency for invasion and recurrence and a natural history of slow growth. Within the intracranial space, there is a narrow capacity for mass expansion. The primary approach for large meningiomas has been resection. Despite a dramatic decline in surgical morbidity for abbreviatioNs CN = cranial nerve; CPA = cerebellopontine angle; GKRS = Gamma Knife radiosurgery; HR = hazard ratio; SRS = stereotactic radiosurgery. submitted January 26, 2014. accepted October 14, 2014. iNclude wheN citiNg Published online December 5, 2014; DOI: 10.3171/2014.10.JNS14198. disclosure The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper. obJect Stereotactic radiosurgery (SRS) has become a common treatment modality for intracranial meningiomas. Skull base meningiomas greater than 8 cm 3 in volume have been found to have worse outcomes following SRS. When symptomatic, patients with these tumors are often initially treated with resection. For tumors located in close proximity to eloquent structures or in patients unwilling or unable to undergo a resection, SRS may be an acceptable therapeutic approach. In this study, the authors review the SRS outcomes of skull base meningiomas greater than 8 cm 3 in volume, which corresponds to a lesion with an approximate diameter of 2.5 cm. methods The authors reviewed the data in a prospectively compiled database documenting the outcomes of 469 patients with skull base meningiomas treated with single-session Gamma Knife radiosurgery (GKRS). Seventy-five patients had tumors greater than 8 cm 3 in volume, which was defined as a large tumor. All patients had a minimum follow-up of 6 months, but patients were included if they had a complication at any time point. Thirty patients were treated with upfront GKRS, and 45 were treated following microsurgery. Patient and tumor characteristics were assessed to determine predictors of new or worsening neurological function and tumor progression following GKRS. results After a mean follow-up of 6.5 years (range 0.5-21 years), the tumor volume was unchanged in 37 patients (49%), decreased in 26 patients (35%), and increased in 12 patients (16%). Actuarial rates of progression-free survival at 3, 5, and 10 years were 90.3%, 88.6%, and 77.2%, respectively. Four patients had new or worsened edema following GKRS, but preexisting edema decreased in 3 patients. In Cox multivariable analysis, covariates associated with tumor progression were 1) presentation with any cranial nerve (CN) deficit from III to VI (hazard ratio [HR] 3.78, 95% CI 1.91-7.45; p < 0.001), history of radiotherapy (HR 12.06, 95% CI 2.04-71.27; p = 0.006), and tumor volume greater than 14 cm 3 (HR 6.86, p = 0.066). In those patients with detailed clinical follow-up (n = 64), neurological function was unchanged in 37 patients (58%), improved in 16 patients (25%), and d...

GKS is an effective treatment option for patients with GJTs, including those with prior surgical resection. Marginal radiation doses greater than 13 Gy may be optimal for tumor control. Longer follow-up will better define the benefits and risks of stereotactic radiosurgery in treating patients with GJT.