Background: The effectiveness of stereotactic radiosurgery (SRS) for cavernous malformation (CM) has not been fully assessed. Consequently, observation is usually recommended when a bleeding CM is initially discovered. Recurrent bleeding occurs with CMs, and these repeat hemorrhages can result in additional morbidity.
Methods: From 1992 to 2011, 49 patients with brainstem CMs were treated with Gamma Knife radiosurgery (GKS). We classified patients into two groups: Group A (n = 31), patients who underwent GKS for a CM following a single symptomatic bleed, and group B (n = 18), patients who underwent GKS for a CM following two or more symptomatic bleeds. The mean marginal dose of radiation was 13.1 Gy (range 9.0-16.8 Gy): 12.8 Gy in group A and 13.7 Gy in group B. The mean follow-up period was 64.0 months (range 1-171 months).
Results: In group A, the annual hemorrhage rate (AHR) following GKS was 7.06 % within the first 2 years and 2.03 % after 2 years. In group B, four patients (22.2 %) developed new or worsening neurologic deterioration as a result of repeat hemorrhages. In group B, the AHR was 38.36 % prior to GKS, 9.84 % within the first two years, and 1.50 % after two years. There was no statistically significant difference in the AHRs at each follow-up period after GKS between the two groups. Adverse radiation effects (AREs) developed in a total of four patients (8.2 %); among them, one patient (2.0 %) developed a permanent case of diplopia. No mortality occurred in this series.
Conclusion: In this study, GKS was demonstrated to be a safe and effective alternative treatment for brain stem CMs that resulted in a reduction in the AHR. Consequently, we suggest that even CM patients who have suffered only a single bleed should not be contraindicated for SRS.