Late adverse radiation effects (ARE) are considered uncommon after stereotactic radiosurgery (SRS) of intracranial arteriovenous malformations (AVM). First reported in the 1990s,1–6 late ARE are distinct from radiation-induced changes (RIC) changes noted in the first 1 to 2 years after AVM SRS (areas of increased signal on T2-weighted magnetic resonance imaging [MRI]) and radiation necrosis.7–11 Late ARE are typically detected 5 or more years after SRS and are characterized by perilesional edema or cyst formation. Whereas patients with small cysts may be asymptomatic, many patients present with symptomatic mass effect requiring surgery to improve their neurological condition.12–16 The incidence of late ARE is thought to be approximately 2% to 6% depending on the length of follow-up after SRS,14,16–19 but the actual rate is poorly understood. In this study, we reviewed AVM patients having SRS at our center between 1990 and 2009 with more than 5 years of MRI follow-up to better determine the incidence of late ARE, and discuss the management of AVM patients with late ARE.
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