2018 Volume 46 Issue 4 Pages 268-274
Gamma Knife radiosurgery (GKRS) for arteriovenous malformation (AVM) is a well-established procedure, and there have been few reports of recurrence or new nidus formation after complete obliteration. To date, we have had to treat three pediatric patients again because of recurrence of radiosurgically treated nidus or formation of a new nidus at a different site. Here, we reviewed these cases and report their pathological features.
The three of our AVM patients are 8, 11, and 13 years-old respectively. Each patients' AVM are found due to either intracerebral or intraventricular hemorrhage. For their first GKRS, 20-25 Gy was delivered to the margin of a nidus 0.08-2.33 ml in volume.
The post GKRS course was uneventful in all cases. In cases 1 and 2, complete obliteration was observed several years after GKRS. However, approximately 1 year later from the complete obliteration, the patients had bleeding because of nidus formation at the same or an adjacent site, and this necessitated a second GKRS. Subsequently, the patients have been followed-up closely, and complete obliteration has been achieved. In case 3, angiography performed approximately 3 years after the first GKRS revealed a residual subtle shunt but verified the disappearance of the nidus. However, angiography also revealed the formation of a new nidus adjacent to the site of the previous one. The patient underwent a second GKRS and complete obliteration was achieved 3 years later.
Obliteration progresses gradually after GKRS for AVM. Our cases suggest that along with obliteration, gradual hemodynamic or other changes also occur simultaneously in the surrounding area, which may result in recurrence or new nidus formation at the same or a different site. Therefore, even after complete obliteration is observed, magnetic resonance imaging should be performed for careful follow-up of patients. Any changes observed should necessarily be evaluated by angiography to exclude the possibility of a new nidus formation.
