Long-term follow-up study of Gamma Knife radiosurgery for arteriovenous malformations with diffuse-type nidi

Abstract

Gamma Knife radiosurgery (GKRS) has been established as an effective treatment modality for arteriovenous malformations (AVMs). A study on the angiographic features of AVMs revealed that a diffuse-type nidus could impede complete obliteration after GKRS. In this study, we evaluated the long-term outcomes of GKRS for diffuse-type nidi and investigated other factors that could affect the prognosis.Methods: Among 598 patients who underwent GKRS for AVM at our institution, 75 patients who were diagnosed with diffuse-type nidi using angiographic imaging were followed. Postoperative outcomes were assessed using magnetic resonance imaging and digital subtraction angiography. Additionally, the patients' demographic characteristics, GKRS profiles, and relevant angiographic features were analyzed to determine other factors that could influence the prognosis.Results: Patients' mean age was 27.9±17.5 years (range: 4-70 years) and the mean follow-up period was 67.8±46.3 months (range: 12-206 months). Complete obliteration of the nidus was seen in 34 patients. Obliteration was observed, on average, 66 months after GKRS. Complications, including postprocedural bleeding and adverse radiation-induced changes, occurred in four patients. A high prescription dose (>23 Gy) was a significant factor for complete obliteration (p=0.032). Age, target volume, and the number of feeding vessels did not have statistically significant impacts on outcomes. Conclusion:The complete obliteration rate of GKRS for AVMs with diffuse-type nidi was 45%. The average time to complete obliteration was over 5 years. Long-term follow-up after GKRS with an appropriate dose is needed for patients with diffuse-type nidi.