Stereotactic helium ion Bragg peak radiosurgery for intracranial arteriovenous malformations. Detailed clinical and neuroradiologic outcome.

89 patients with angiographically documented arteriovenous malformations were treated with helium ion Bragg peak radiation. The rate of complete angiographic obliteration 2 years after radiation was 94% in those lesions smaller than 4 cm3 (2.0 cm in diameter), 75% for those 4-25 cm3 and 39% for those larger than 25 cm3 (3.7 cm in diameter); at 3 years after radiation, the corresponding obliteration rates were 100, 95 and 70%. Major clinical complications occurred in 10 patients (8 permanent, 2 transient) between 3 and 21 months after treatment; all were in the initial stage of the protocol (higher radiation doses). 10 patients bled from residual malformation between 4 and 34 months after treatment. Seizures were improved in 63% and headaches in 68% of patients. Excellent or good clinical outcome was achieved in 94% of patients. Compared to the natural history and risks of surgery for these difficult malformations, we consider these results encouraging. Heavy-charged-particle radiation is a valuable therapy for surgically inaccessible symptomatic cerebral arteriovenous malformations. The current procedure has two disadvantages: the prolonged latent period before complete obliteration and the small risk of serious neurological complications.