Gamma Knife surgery of meningiomas located in the posterior fossa: factors predictive of outcome and remission

Clinical article

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Although numerous studies have analyzed the role of stereotactic radiosurgery for intracranial meningiomas, few studies have assessed outcomes of posterior fossa meningiomas after stereotactic radiosurgery. In this study, the authors evaluate the outcomes of posterior fossa meningiomas treated with Gamma Knife surgery (GKS). The authors also assess factors predictive of new postoperative neurological deficits and tumor progression.


A retrospective review was performed of a prospectively compiled database documenting the outcomes of 152 patients with posterior fossa meningiomas treated at the University of Virginia from 1990 to 2006. All patients had a minimum follow-up of 24 months. There were 30 males and 122 females, with a median age of 58 years (range 12–82 years). Seventy-five patients were treated with radiosurgery initially, and 77 patients were treated with GKS after resection. Patients were assessed clinically and radiographically at routine intervals following GKS. Factors predictive of new neurological deficit following GKS were assessed via univariate and multivariate analysis, and Kaplan-Meier analysis and Cox multivariate regression analysis were used to assess factors predictive of tumor progression.


Patients had meningiomas centered over the tentorium (35 patients, 23%), cerebellopontine angle (43 patients, 28%), petroclival region (28 patients, 18%), petrous region (6 patients, 4%), and clivus (40 patients, 26%). The median follow-up was 7 years (range 2–16 years). The mean preradiosurgical tumor volume was 5.7 cm3 (range 0.3–33 cm3), and mean postradiosurgical tumor volume was 4.9 cm3 (range 0.1–33 cm3). At last follow-up, 55 patients (36%) displayed no change in tumor volume, 78 (51%) displayed a decrease in volume, and 19 (13%) displayed an increase in volume. Kaplan-Meier analysis demonstrated radiographic progression-free survival at 3, 5, and 10 years to be 98%, 96%, and 78%, respectively. In Cox multivariable analysis, pre-GKS covariates associated with tumor progression included age greater than 65 years (hazard ratio [HR] 3.24, 95% CI 1.12–9.37; p = 0.03) and a low dose to the tumor margin (HR 0.76, 95% CI 0.60–0.97; p = 0.03), and post-GKS covariates included shunt-dependent hydrocephalus (HR 25.0, 95% CI 3.72–100.0; p = 0.001). At last clinical follow-up, 139 patients (91%) demonstrated no change or improvement in their neurological condition, and 13 patients showed symptom deterioration (9%). In multivariate analysis, the only factors predictive of new or worsening symptoms were clival or petrous location (OR 4.0, 95% CI 1.1–13.7; p = 0.03).


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.

Abbreviations used in this paper: CN = cranial nerve; CPA = cerebellopontine angle; GKS = Gamma Knife surgery; HR = hazard ratio; PFS = progression-free survival.

Article Information

Address correspondence to: Jason P. Sheehan, M.D., Ph.D., Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia 22908. email:

Please include this information when citing this paper: published online January 7, 2011; DOI: 10.3171/2010.11.JNS101193.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Upper: Axial, coronal, and sagittal T1-weighted MR images obtained prior to GKS treatment show a 1.2-cm3 meningioma centered over the right tentorium. Lower: Images obtained 30 months posttreatment demonstrate a decrease in tumor volume to 0.6 cm3.

  • View in gallery

    Upper: Axial, coronal, and sagittal T1-weighted MR images obtained prior to GKS treatment show an 8.7-cm3 meningioma centered over the right CPA. Lower: Images obtained 74 months after treatment demonstrate a decrease in tumor volume to 5.8 cm3.

  • View in gallery

    Upper: Axial, coronal, and sagittal T1-weighted MR images obtained prior to GKS treatment demonstrate a 10.2-cm3 meningioma centered over the petroclival region at the petrous apex. Lower: Images obtained 38 months after treatment show a decrease in tumor volume to 5.2 cm3.

  • View in gallery

    Upper: Axial T1-weighted MR images obtained prior to GKS treatment demonstrate a 2.1-cm3 meningioma centered over the left petrous ridge. Lower: Images obtained 39 months posttreatment show a decrease in tumor volume to 1.7 cm3.

  • View in gallery

    Upper: Axial, coronal, and sagittal T1-weighted MR images obtained prior to GKS treatment show a 17-cm3 meningioma centered over the clivus. Lower: Images obtained 54 months after treatment demonstrate no change in tumor volume (17 cm3).

  • View in gallery

    Graph of tumor PFS following GKS.

  • View in gallery

    Graph of tumor PFS following GKS in patients with and without a previous history of surgery.


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