Four-Dimensional Flow MRI Analysis of Cerebral Blood Flow Before and After High-Flow Extracranial-Intracranial Bypass Surgery With Internal Carotid Artery Ligation

BACKGROUND The hemodynamic changes that occur after high-flow (extracranial-intracranial) EC-IC bypass surgery with internal carotid artery (ICA) ligation are not well known. OBJECTIVE To assess blood flow changes after high-flow EC-IC bypass with ICA ligation by time-resolved 3-dimensional phase-contrast (4D Flow) magnetic resonance imaging (MRI). METHODS We enrolled 11 patients who underwent high-flow EC-IC bypass. 4D Flow MRI was performed before and after surgery to quantify the blood flow volume (BFV) of the ipsilateral ICA (BFViICA), bypass artery (BFVbypass), contralateral ICA (BFVcICA), and basilar artery (BFVBA). Subsequently, we calculated the total BFV (BFVtotal=BFViICA+BFVcICA+BFVBA [before surgery], BFVcICA+BFVBA+BFVbypass [after surgery]). The BFV changes after bypass was statistically analyzed. RESULTS BFVbypass was slightly lower than BFViICA, but the difference was not statistically significant (3.840.94 vs 4.42 +/- 1.38 mL/s). The BFVcICA and BFVBA significantly increased after bypass surgery (BFVcICA 5.89 +/- 1.44 vs 7.22 +/- 1.37 mL/s [P=.0018], BFVBA 3.06 +/- 0.41 vs 4.12 +/- 0.38 mL/s [P<.001]). The BFVtotal significantly increased after surgery (13.37 +/- 2.58 vs 15.18 +/- 1.77 mL/s [P=.015]). There was no evidence of hyperperfusion syndrome in any cases. CONCLUSION After high-flow EC-IC bypass with permanent ICA ligation, the bypass artery could partially compensate for the loss of BFV of the sacrificed ICA. The increased flow of the contralateral ICA and BA supply collateral blood flow. Clinically irrelevant hyperperfusion was observed.