P03.06 Cavernous malformations of the brainstem: radiosurgical management with gamma knife

Abstract BACKGROUND About 20% of intracranial cavernous malformations (CM) occur in the brainstem. The greatest risk of brainstem CM is hemorrhage which can be devastating and even fatal in this location. The optimal management for these lesions would naturally be microsurgical resection. However, surgery in this location is associated with significant morbidity and mortality. Gamma knife radiosurgery provides a safer alternative. The purpose of this study is to investigate the efficacy of gamma knife radiosurgery for brainstem CM in preventing bleeding, as well as, assess safety with regards to radiation-induced complications. Additionally, we aimed to evaluate the feasibility and safety of volume-staged gamma knife radiosurgery for larger CM in the brainstem. MATERIAL AND METHODS Between September 2007 and August 2017, 48 patients with brainstem CM were treated by gamma knife. Thirty-two patients were available for follow up of at least one year. A total of 33 lesions were treated (one patient had two brainstem CM). Twenty-eight patients had at least one hemorrhagic event before radiosurgery. The patients underwent 40 gamma knife sessions. These included 28 single sessions (including two sessions for same patient for 2 different lesions in pons). Five patients had volume-staged gamma knife treatments due to the large size of the CM. The median total CM volume/lesion was 0.8 cc (0.1–30.4 cc), while the median target volume/session was 1 cc (0.1–11.5 cc). The median prescription dose was 12 Gy (10–14 Gy). RESULTS The mean follow up after treatment was 40 months (12–95 months). The annual hemorrhage rate (AHR) before gamma knife radiosurgery was 25.5%. After treatment there were a total of 5 hemorrhagic events with an overall AHR of 4.5%. Three hemorrhagic events occurred in the first 2 years after treatment with an AHR of 2.7% and 2 events more than 2 years after treatment with an AHR of 2.2%. No hemorrhagic events occurred among the patients treated by volume-staged radiosurgery. Clinical improvement was observed in 15 (46.9%) patients. Temporary adverse radiation events developed in 6 patients (19%). CONCLUSION Gamma knife radiosurgery provides an effective and safe treatment alternative to surgery for brainstem CM. Volume-staged gamma knife radiosurgery for brainstem CM appears to be a viable option for larger CM.