Hemorrhagic Vulnerability of Lenticulostriate Artery–Supplied Arteriovenous Malformations After Radiosurgery: De Novo Aneurysm Formation on Distal Feeders

BACKGROUND AND OBJECTIVES: Deep arteriovenous malformations (AVMs) carry a substantial risk of hemorrhage during the latency period after Gamma Knife radiosurgery (GKRS). We hypothesized that arterial supply involving the lenticulostriate arteries (LSAs), which are representative fragile perforating arteries, contributes to this vulnerability. This study investigated the hemorrhagic propensity and angiographic changes in LSA-supplied AVMs. METHODS: In this retrospective case series, we identified 13 patients with LSA-supplied AVMs from a database of 140 patients who underwent GKRS between 2010 and 2026. We calculated the annualized hemorrhage rate during the latency period and evaluated emergency angiographic findings to determine precise bleeding sources. RESULTS: Over 97.9 person-years of observation, latency-period hemorrhage occurred in 5 of 13 patients (38.5%), yielding a high annualized hemorrhage rate of 11.5%. Hemorrhages occurred at a median of 45 months post-GKRS (range, 5-73 months). Clinical presentations were severe (Glasgow Coma Scale score: 3-9), frequently complicated by intraventricular hemorrhage and acute hydrocephalus. Three patients required extraventricular drainage, and one died before intervention. In 4 evaluated cases, emergency angiography identified the bleeding source as de novo aneurysms (diameter, 2-4 mm) on distal feeders (LSAs, n = 3; posterior pericallosal artery, n = 1) that were absent pre-GKRS. All ruptured aneurysms were occluded by targeted transarterial embolization. The median functional deterioration (change in modified Rankin Scale) in the hemorrhage group was +2. Conversely, the 8 hemorrhage-free patients developed no aneurysms over a median follow-up of 96 months. Favorable functional outcomes (modified Rankin Scale 0-2) were achieved in 9 patients (69.2%) overall. CONCLUSION: LSA-supplied AVMs carry a high risk of latency-period hemorrhage, primarily driven by de novo distal feeder aneurysms. This vulnerability stems from a complex interplay of inherent structural fragility, persistent hemodynamic stress, and radiation-induced vasculopathy. Precise imaging of the distal feeder architecture enables targeted transarterial embolization as an effective bridge therapy before nidus obliteration.