Hemodynamic flow patterns evaluated by transcranial color-coded duplex sonography after STA-MCA bypass for internal carotid artery occlusion

Extracranial-intracranial (EC-IC) bypass surgery had been widely performed for the treatment of internal carotid artery occlusion. However, it is presently difficult to predict how the bypass flow will contribute to intracranial circulation. We examined intracranial hemodynamics by transcranial color-coded duplex sonography (TCCD) after superficial temporal artery (STA)-middle cerebral artery (MCA) bypass and retrospectively studied the relationship between the postoperative contribution of the bypass flow and the preoperative collateral circulation and cerebrovascular perfusion status in 10 patients. Hemodynamics in the MCA detected by TCCD were classified into three patterns. In pattern A, perfusion of the whole MCA area is completely dependent on the bypass flow. In pattern B, perfusion of the M2 segment is dependent on the bypass flow, but perfusion of the M1 segment is independent of the bypass flow. In pattern C, perfusion of the whole MCA area is supplied by collateral flow and the bypass does not function efficiently. Preoperative absence of collateral flow via anterior communicating artery and cerebral perfusion status type 3 (reduced regional cerebral blood flow and regional cerebral vasoreactivity) seems to predict hemodynamic usefulness of the bypass flow after surgery. TCCD is an easy and noninvasive method for evaluating intracranial cerebral circulation after EC-IC bypass surgery.