Long-term outcomes after Gamma Knife surgery for vestibular schwannomas: a 10-year experience

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Object

The authors sought to assess the results of Gamma Knife surgery (GKS) in patients with vestibular schwannomas (VSs).

Methods

Seventy-four consecutive patients (33 men and 41 women) were evaluated by means of serial imaging studies, clinical examinations, and questionnaires. Nineteen patients had undergone resection of their VS. Facial nerve function was normal in 63 patients (85.1%) before GKS, and 63.5% of them had useful hearing. The prescription peripheral dose varied between 10 and 14 Gy (mean 12.27 ± 0.96 Gy); the corresponding central dose was 21 to 30 Gy (mean 24.9 ± 2.18 Gy). The mean volume of the tumor at GKS was 10.79 ± 5.52 ml (range 0.11–27.8 ml). A mean of eight isocenters (range 3–17) was used for treating these lesions.

At a median follow-up period of 68.3 months (range 30–122 months), tumor shrinkage was observed in 60 patients (81.1%), and the tumor size was stable in 11 (14.8%). Persistent neuroimaging demonstrated evidence of progression in only three patients (4.1%): two underwent repeated GKS after an interval of 18 months and one continues to be observed. Five patients experienced trigeminal dysfunction: in three the dysfunction was transient and in the other two the dysfunction persists. Three patients suffered facial palsy. Useful hearing was preserved in 34 patients. Thirteen patients experienced some degree of hearing improvement. Deterioration of hearing was found in 13 of 62 patients who had Class I or II hearing before treatment.

Conclusions

Gamma Knife surgery prevents tumor growth; it achieves excellent neurological function preservation and produces few treatment-related complications.

Abbreviations used in this paper: GKS = Gamma Knife surgery; MR = magnetic resonance; VS = vestibular schwannoma.

Article Information

Address reprint requests to: Dong Liu, M.D., Gamma Knife Center, Department of Neurosurgery, Tianjin Medical University Second Hospital, 23# Pingjiang Road, Hexi District, Tianjin , China, 300211. email: tjliudong@yahoo.com.cn.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Scatterplot showing tumor volume compared with tumor margin dose in 74 patients with VSs treated by GKS.

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    Serial contrast-enhanced axial T1-weighted MR images obtained in a 52-year-old man. A: A pre-GKS image of the cystic VS. B: Image obtained 6 months post-GKS. C: Image obtained 12 months post-GKS. D: Image obtained 24 months post-GKS. E: Image obtained 60 months post-GKS. Note the continuing tumor regression over time.

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    Serial contrast-enhanced axial T1-weighted images obtained in a 48-year-old man. A: A pre-GKS image revealing a solid VS. B: Image obtained 6 months post-GKS. C: Image obtained 24 months post-GKS. D: Image obtained 48 months post-GKS. Note the loss of central contrast enhancement and the transient enlargement of the tumor; later (C and D) the central contrast enhancement is homogeneous again.

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    Kaplan–Meier plot showing imaging-defined local control of VSs after GKS.

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