Gamma Knife surgery for large vestibular schwannomas: a single-center retrospective case-matched comparison assessing the effect of lesion size

Clinical article

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Gamma Knife surgery (GKS) is a safe and effective treatment for patients with small to moderately sized vestibular schwannomas (VSs). Reports of stereotactic radiosurgery for large VSs have demonstrated worse tumor control and preservation of neurological function. The authors endeavored to assess the effect of size of VSs treated using GKS.


This study was a retrospective comparison of 24 patients with large VSs (> 3 cm in maximum diameter) treated with GKS compared with 49 small VSs (≤ 3 cm) matched for age, sex, radiosurgical margin and maximal doses, length of follow-up, and indication.


Actuarial tumor progression-free survival (PFS) for the large VS cohort was 95.2% and 81.8% at 3 and 5 years, respectively, compared with 97% and 90% for small VSs (p = 0.009). Overall clinical outcome was better in small VSs compared with large VSs (p < 0.001). Patients with small VSs presenting with House-Brackmann Grade I (good facial function) had better neurological outcomes compared with patients with large VSs (p = 0.003). Treatment failure occurred in 6 patients with large VSs; 3 each were treated with resection or repeat GKS. Treatment failure did not occur in the small VS group. Two patients in the large VS group required ventriculoperitoneal shunt placement. Univariate analysis did not identify any predictors of treatment failure among the large VS cohort.


Patients with large VSs treated using GKS had shorter PFS and worse clinical outcomes compared with age-, sex-, and indication-matched patients with small VSs. Nevertheless, GKS has efficacy for some patients with large VSs and represents a reasonable treatment option for selected patients.

Abbreviations used in this paper:GKS = Gamma Knife surgery; PFS = progression-free survival; SRS = stereotactic radiosurgery; VP = ventriculoperitoneal; VS = vestibular schwannoma.

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 May 24, 2013; DOI: 10.3171/2013.4.JNS122195.

© AANS, except where prohibited by US copyright law.



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    Actuarial PFS dichotomized into large (> 3 cm) and small (≤ 3 cm) VSs treated using GKS.

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    Clinical outcome of the large VS cohort stratified by symptoms and signs at presentation. Upper: Clinical outcome of cases presenting with trigeminal neuropathy. Lower: Clinical outcome of cases stratified by the presenting facial nerve function.

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    An illustrative case of a typical patient treated using GKS for a large VS. This was a 74-year-old woman who presented with hydrocephalus. She underwent VP shunt placement prior to GKS. She did not have useful hearing in her left ear. She had House-Brackmann Grade V facial function on the left at presentation. The patient remained clinically stable throughout her 4-year follow-up. Preoperative axial (A–C), coronal (D), and sagittal (E) MRI is displayed in the first row (A–E) with comparative 4-year follow-up MRI displayed in the second row (F–J). A: A T1-weighted image through the level of the lateral ventricles demonstrating ventriculomegaly. B: A constructive interference in steady-state sequence depicting a left cerebellopontine angle lesion effacing the brainstem and causing mass effect on the fourth ventricle. C–E: These T1-weighted images obtained after contrast administration depict heterogeneous contrast enhancement. F: A T2-weighted image through the level of the lateral ventricles demonstrating diminished size of the lateral ventricles and no evidence of transependymal flow. G: Constructive interference in steady-state sequence demonstrating stable tumor size, brainstem effacement, and fourth ventricle mass effect. H–J: These T1-weighted images obtained after contrast administration demonstrate slightly decreased tumor size with cyst formation.



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