Gamma-knife radiosurgery for brainstem arteriovenous malformations. Preliminary results

Background and purpose. Microsurgical resection have the advantage to be im mediately effective according to bleeding risk and is the reference treatme nt for cerebal arteriovenous malformations For cerebral arteriovenous malfo rmations located in the brainstem gamma-knife radiosurgery due to its low i nvasivity is classically a first line treatment. We reviewed the Marseilles experience to assess the efficacy and safety of gamma-knife radiosurgery f or brain stem arteriovenous malformations. Methods. We analyzed retrospectively data of 45 patients with an arteriover zous malformation located in the brain stem treated in Marseilles by gamma- knife radiosurgery by between 07/92 and 12/99. Mean age was 42years, there were 5 children. Arteriovenous malformations were located in the pens or mi dbrain for the majority of the patients. Intraaxial lesion was found in 82 % of patients. Hemorrhage prior to radiosurgery occurred in 75 % of the pat ients. Gamma-knife procedure was the first treatment of the arteriovenous m alformations for 29 patients (65 %); previous surgery was performed in 34 p atients (15 %). Mean nidus volume was 550 mm(3) (32-14 196 mm(3)). Mean mar gin nose was of 23 Gy (range 15-30 Gy). Follow up was available for 25 pati ents (mean 18 months). Results. One patient presenred a transient worsening of his neurological st atus, and 2 patients developed a fixed deficit. Two patients underwent rebl eeding at an interval of 12 to 36 months after the gamma-knife procedure. A t last angiographic follow-up (13 patients), the obliteration rate was 82 % of the arteriovenous malformations. A second procedure was proposed to a p atient with only partial occlusion at 3 years. Conclusions. Gamma-knife radiosurgery can achieve good obliteration rate of brain stem arteriovenous malformations with low morbidity and may be a val uable first-choice therapy for such arteriovenous malformations; A larger p opulation and longer follow lip are mandatory in order to confirm these pre liminary results.