Diagnostic Values of the "To and Fro" Conflict Sign on Intraoperative Indocyanine Green Video Angiography as a Warning Sign of the Focal Cerebral Hyperperfusion and Watershed Shift Phenomenon after Superficial Temporal Artery-Middle Cerebral Artery Bypass for Adult Patients with Moyamoya Disease

Introduction: The focal cerebral hyperperfusion (CHP) is a potential complication after superficial temporal artery-middle cerebral artery (STA-MCA) bypass for moyamoya disease (MMD) that can result in delayed intracerebral hemorrhage and/or neurological deterioration. The focal CHP could accompany hemodynamic ischemia due to the "watershed shift (WS) phenomenon." Preoperative prediction of the focal CHP and WS phenomenon remains challenging. Here, we aimed to assess the diagnostic value of the "to and fro" conflict sign, conflicting blood flow around the vascular territory of the recipient arteries on an indocyanine green video angiography (ICG-VA) for predicting the focal CHP and WS phenomenon. Methods: Ninety-seven consecutive adult patients with MMD, undergoing 106 surgeries, were enrolled. Serial quantitative analysis of cerebral blood flow was routinely conducted using n-isopropyl-p-[123I] iodoamphetamine single-photon emission computed tomography preoperatively and postoperative day 1 and 7 after STA-MCA bypass. The association between the "to and fro" conflict sign on ICG-VA and the focal CHP/WS phenomenon incidence was then analyzed. Results: The incidence of the focal CHP and WS phenomenon was 29.2% (31/106) and 10.4% (11/106), respectively. The "to and fro" conflict sign was evident in 35.5% (11/31) and 54.5% (6/11) of MMD patients with the focal CHP and WS phenomenon, respectively. The "to and fro" conflict sign was significantly associated with both the focal CHP and WS phenomena. Conclusion: The "to and fro" conflict sign on ICG-VA may serve as an intraoperative warning sign of the focal CHP and WS phenomenon after STA-MCA bypass in adult patients with MMD, providing neurosurgeons with a valuable tool for early detection. Cerebral hyperperfusion is a major complication after revascularization surgery for MMD. It is challenging to accurately predict postoperative hemodynamics after revascularization surgery for MMD. This study demonstrated the usefulness of "to and fro" conflict sign on intraoperative indocyanine green angiography, which is easily recognized without any further analysis.