Delayed Mass after Gamma Knife Surgery for Cerebral Arteriovenous Malformations: Two Case Reports

Abstract

Here we report two cases of a delayed mass after gamma knife surgery (GKS) for a cerebral arteriovenous malformation (AVM). Case 1 involved a 71-year-old man who had been treated with GKS for a ruptured AVM at 63 years of age. Computed tomography showed a cystic formation 2 years after the GKS. Magnetic resonance imaging 68 months later revealed a round mass in the irradiated area. The mass gradually increased in size and was resected 8 years after the GKS. Histological examination identified an expanding hematoma. Case 2 involved a 12-year-old girl who had been treated with GKS for a ruptured left occipital AVM diagnosed as Osler-Weber-Rendou disease at 5 years of age in another hospital. She presented with high fever, nausea, and general fatigue caused by an abscess in the left frontal lobe and a round mass with edema in the left occipital lobe. With conservative treatment, the frontal abscess disappeared and the occipital mass gradually reduced 3 months later. She was discharged without neurological deficits after 72 days. Our results show that serial long-term follow up is necessary, even if angiographic obliteration has been achieved after GKS for AVM.