Gamma Knife surgery for posterior fossa arteriovenous malformations

Purpose: The long-term outcomes after Gamma Knife surgery (GKS) were retrospectively analyzed in patients with posterior fossa arteriovenous malformations (AVMs) to evaluate the efficacy, safety, and indications for this procedure.Methods: The medical records were reviewed of 75 patients who underwent GKS between 1992 and 2005 in our institution. Results: The rate of complete AVM obliteration was 57.3% at 3 years and 80.2% at 5 years after GKS. Multivariate analysis showed that the significant factors for higher obliteration rates were younger patient age, smaller nidus volume, and smaller nidus maximum/minimum diameter. Two patients suffered hemorrhages during the latency interval. Clinical deterioration was observed in 10 patients with radiation-induced edema after the GKS. Larger nidus volume and AVM located adjacent to eloquent areas were significantly associated with the risk of neuropathy after GKS. One patient developed radiation-induced necrosis 4 years after confirmation of complete AVM obliteration. Conclusions: GKS is an effective and safe modality for the treatment of posterior fossa AVMs, resulting in high AVM obliteration rate with low complication rates based on neuroimaging and neurological symptoms. Posterior fossa AVMs tend to occur adjacent to eloquent areas, so we recommend preparing a conformed dose plan that considers both obliteration of the AVM nidus and preservation of neurological function.