Impact of intraoperative cortical indocyanine green extravasation on local vasogenic edema immediately after direct revascularization in an adult with moyamoya disease: illustrative case

BACKGROUND Local vasogenic edema induced after direct revascularization in moyamoya disease (MMD) is associated with blood–brain barrier dysfunction, potentially leading to postoperative cerebral hyperperfusion (CHP) or delayed intracerebral hemorrhage. This phenomenon allows the leakage of fluids, proteins, and other substances from the blood vessels into the extracellular compartment. Typically, such edema is observed postoperatively rather than intraoperatively. OBSERVATIONS A 48-year-old female with ischemic-onset MMD underwent revascularization on her left hemisphere with Suzuki’s angiographic stage III. Direct bypass was successfully performed, as confirmed by intravenous indocyanine green (ICG) video angiography. Subsequently, ICG extravasation was observed near the anastomosis site, despite the absence of cortical injury or bleeding under white light microscopy. Postoperative radiological imaging showed reversible pure vasogenic edema in the corresponding area, with no evidence of CHP. The patient did not exhibit neurological deterioration and was discharged home on postoperative day 16. LESSONS ICG, characterized by low molecular weight, water solubility, and high affinity with plasma proteins, can extravasate, serving as a direct indication of local vasogenic edema induced by direct revascularization in MMD. To enhance comprehension of the vulnerability of the blood–brain barrier in MMD, it is advisable to gather cases with prolonged observations of ICG video angiography after direct revascularization.