Supplementary Material for: Occult Brain Arteriovenous Malformation Superimposed on a Pial Arteriovenous Fistula: Case Report

Introduction: Pial arteriovenous fistulas are characterized by an abnormal connection between an intracranial artery and vein without an intervening nidus. Their predominant symptoms largely arise from mass effect, shunting, or hemorrhage. Most conservatively managed cases progress to death, but endovascular and/or surgical intervention is often successful. Case Presentation: We present the unique case of a 15-year-old girl with spontaneous intracranial hemorrhage from a single-vessel arteriovenous fistula. Although preoperative imaging failed to show a distinct nidus, intraoperative indocyanine green angiography performed after successful clipping of the primary fistulous site revealed residual shunting from a peri-lesional arteriovenous malformation. Discussion/Conclusion: This case demonstrates the importance of intraoperative imaging and meticulous circumferential inspection of these lesions to detect residual vascular shunting.