Microsurgical management of delayed radiation injury after arteriovenous malformation radiosurgery: An experience-based analysis

Background: Radiation necrosis (RN) is a recognized adverse effect of stereotactic radiosurgery (SRS) for brain arteriovenous malformations (AVMs), conventionally considered an early or subacute complication. However, late RN occurring years after treatment remains poorly characterized, particularly in AVM populations. We aimed to describe the clinical presentation, radiological features, surgical indications, and outcomes of patients undergoing microsurgical management for delayed radiation injury after AVM radiosurgery. Methods: We performed a retrospective single-center study of consecutive patients who underwent microsurgical resection for delayed radiation-related complications following SRS for intracranial AVMs. Delayed injury was defined as symptomatic radiological changes occurring more than 5 years after SRS or progressive radiation-related pathology beyond the expected early posttreatment period. Clinical data, imaging findings, angiographic status, surgical indications, histopathology, and functional outcomes (modified Rankin Scale) were analyzed. Results: Five patients (age range 29–69 years) underwent surgery between 3 and 21 years after SRS. Presenting symptoms included progressive focal deficits ( n = 3), refractory seizures ( n = 3), and severe headache with mass effect ( n = 2); one patient required urgent decompression. Magnetic resonance imaging demonstrated extensive T2/Fluid-attenuated inversion recovery hyperintensity and vasogenic edema in all cases, with cystic changes in two. Angiography confirmed complete AVM obliteration in three patients and residual nidus in two. No surgical complications occurred. At ≥6 months follow-up, all patients showed neurological stabilization or improvement, with no new permanent deficits and improved seizure control. Conclusion: Late RS after AVM radiosurgery is an underrecognized long-term complication that may occur years or decades after treatment, even after angiographic cure. In selected patients with progressive or refractory symptoms, microsurgical resection is a safe and effective strategy that can provide symptom relief and favorable functional outcomes. Long-term surveillance is essential in this population.