Case Series of Intraoperative Indocyanine Green Angiography Findings in Minimally Invasive Surgical Ligation of Cerebrospinal Fluid-Venous Fistulas

BACKGROUND AND OBJECTIVES: Spontaneous intracranial hypotension is a debilitating condition resulting from cerebrospinal fluid (CSF) loss. Spontaneous CSF leaks are classified as ventral dural defects (Type 1), meningeal diverticula (Type 2), and CSF-venous fistulas (CVFs, Type 3). CVFs are recently described, diagnostically challenging, and poorly understood intraoperatively. We present a technical note involving 8 patients undergoing intraoperative indocyanine green (ICG) angiography during CVF ligation. METHODS: We conducted a retrospective review of consecutive patients undergoing minimally invasive CVF repair with preligation and postligation ICG angiography between October 2024 and March 2025, performed by a single surgeon at a tertiary care center. Outcomes were assessed using chart review. RESULTS: Eight patients underwent CVF ligation with diverticulum wrapping at 11 spinal levels, without perioperative complications. Twenty-two intravenous ICG doses were administered without adverse events. Preligation ICG revealed avid enhancement of the diverticulum in all cases. Postligation ICG showed superficial, sluggish enhancement likely reflecting vasa nervorum. All patients experienced clinical improvement and radiographic resolution of spontaneous intracranial hypotension at the 6-week follow-up. CONCLUSION: ICG angiography during CVF ligation is a novel application of an established intraoperative imaging tool. Preligation enhancement consistently localized the fistula, while postligation imaging confirmed disconnection. These findings raise the hypothesis of bidirectional flow between the diverticulum and venous system, with potential diagnostic and pathophysiological implications. These observations should be considered hypothesis-generating and require validation in larger cohorts. A larger study is underway to further correlate ICG patterns with microsurgical anatomy.