[Cyberknife radiosurgery for cerebral arteriovenous malformations: outlining of the radiosurgical target and obliteration].

Objective: To explore the therapeutic outcomes of cyberknife for patients with arteriovenous malformations (AVM) and outline the content of AVM targets.

Methods: Between January 2008 and October 2011, 51 patients underwent cyberknife radiosurgery for cerebral AVMs. The mean age was 27 (8-47) years. The procedures included prior embolization (n = 24), gamma knife before cyberknife (n = 2) and cyberknife initially (n = 25). The delineation of AVM targets was as follows: AVM with prior embolization, radiosurgical targets included AVM nidus, embolization areas and some small draining veins. However, low radiation dose was delivered to embolization parts and draining veins. For 25 patients without embolization, the radiosurgical target was AVM nidus. The mean target volume was 7.8 (1.2-22.0) cm³ and 15 of them were larger than 10.0 cm³. In patients harboring AVM with target volumes < 4 cm³, cyberknife radiation was delivered in a single session. And the remainder had 2 (n = 25) or 3 (n = 19) sessions. The mean marginal dose was 23(18-28) Gy.

Results: AVM obliteration was confirmed by magnetic resonance imaging (MRI) or angiography in 40 (78%) patients during a mean follow-up of 46 (36-70) months. Marked size reduction of AVM was obtained in 11 incompletely obliterated patients. Among them, there were second cyberknife treatment (n = 3), third embolization for complex AVM (n = 1), gamma knife (n = 1) and further follow-ups (n = 6). The higher obliteration rate of AVM was correlated with small volume of AVM in noncritical areas, prior embolization and radiation target of embolization areas. Three patients had hemorrhage during the follow-up period and recovered. Brain edema was found in patients with basal ganglion or parietal AVMs. A permanent neurological deficit (paralysis) due to adverse radiation effects developed in 1 patient.

Conclusion: Cyberknife radiosurgery is particularly effective for patients with smaller AVMs in noncritical areas of brain. In patients with prior embolization, delineation of AVM targets including embolization areas is essential for a higher rate of obliteration.