Time-of-flight MRA signal intensity predicts the cerebral hemodynamic status after superficial temporal artery to middle cerebral artery anastomosis.

Arterial signal intensities on magnetic resonance angiography (MRA) correlate with the relevant hemisphere's hemodynamics in patients with cerebrovascular diseases. We evaluated whether superficial temporal artery (STA) signal intensities (SI) on MRA were useful to evaluate the postoperative cerebral hemodynamics of patients with symptomatic internal carotid artery (ICA) or middle cerebral artery (MCA) steno-occlusive disease who underwent unilateral STA-MCA anastomosis. Twenty-one consecutive patients undergoing unilateral STA-MCA anastomosis for symptomatic ICA or MCA steno-occlusive disease were enrolled. All patients underwent MRA and superficial temporal artery duplex ultrasonography (STDU) at 3 months and 1 year postoperatively. Bilateral region of interests (ROIs) on time-of-flight (TOF)-MRA source images were placed on the STA just before its bifurcation. The STA-SI ratio, which was the ratio of the SI on the operated STA to that of the contralateral STA, was calculated; the correlation between the ratio and STDU parameters was investigated. The STA diameter and flow velocities (systolic, end-diastolic, and mean) significantly correlated with the STA-SI ratio at 1 year postoperatively (p = .0302, p = .0002, p = .0029, p = .002). The end-diastolic flow velocity ratio was significantly correlated with the STA-SI ratio at 1 year postoperatively (p = .0014, r = 0.6518). The STA-SI ratio can be used to predict the extent of postoperative collateral bypass flow, and it may help predict postoperative cerebrovascular reserve.