Importance of collateral venous circulation on indocyanine green videoangiography in intracranial meningioma resection: direct evidence for venous compression theory in peritumoral edema formation.

OBJECTIVE Indocyanine green videoangiography (ICGVA) has been used in many neurosurgical operations, including vascular and brain tumor fields. In this study, the authors applied ICGVA to intracranial meningioma surgery and evaluated it usefulness with attention to collateral venous flow. METHODS Forty-two patients with intracranial meningioma who underwent ICGVA during microsurgical resection were retrospectively analyzed. For ICGVA, the ICG was injected intravenously at the standard dose of 12.5 mg before and/or after tumor resection. Intravascular fluorescence from blood vessels was imaged through a microscope with a special filter and infrared excitation light to illuminate the operating field. The authors assessed the benefits of ICGVA and analyzed its findings with preoperative radiological findings on MRI. RESULTS ICGVA allowed real-time assessment of the patency and flow direction in very small peritumoral vessels in all cases. A safe dural incision could also be done based on information from ICGVA. The collateral venous channel due to venous obstruction of tumoral compression was found in 10 cases, and venous flow restoration after tumor resection was observed promptly after tumor resection in 4 cases. Peritumoral brain edema (PTBE) was observed on preoperative T2-weighted MRI in 19 patients. The presence of collateral venous circulation or flow restoration was significantly related to PTBE formation in multivariate analysis (p = 0.001; HR 0.027, 95% CI 0.003-0.242). CONCLUSIONS ICGVA, an excellent method for monitoring blood flow during meningioma resection, provides valuable information as to the presence of venous collaterals and flow restoration. Furthermore, the fact that the presence of venous collaterals was found to be associated with PTBE may directly support the venous theory as the pathogenesis of PTBE formation.