Superficial Temporal Artery Duplex Ultrasonography for Improved Cerebral Hemodynamics after Extracranial-Intracranial Bypass Surgery

Abstract

Background: To investigate the utility of superficial temporal artery (STA) duplex ultrasonography (STDU) for evaluating the improvement of the cerebral hemodynamics after extracranial-intracranial (EC-IC) bypass. Methods: This study included 40 consecutive patients who underwent EC-IC bypass for occlusive disease of cerebral arteries. STDU was performed to measure the flow velocity, pulsatility index, and diameter of the operated STA before and 14 days after EC-IC bypass. Regional cerebral blood flow (rCBF) and acetazolamide (ACZ) reactivity of the ipsilateral middle cerebral artery (MCA) territory were evaluated by quantitative single-photon emission computed tomography with the ACZ challenge test. We investigated the correlation between STA flow velocity/diameter and rCBF/ACZ reactivity in the ipsilateral MCA territory. Results: Mean flow velocity (MFV; 26.3 ± 8.8 to 55.3 ± 16.3 cm/s, p < 0.0001) and diameter (1.57 ± 0.24 to 2.26 ± 0.29 mm, p < 0.0001) of the STA, and rCBF (29.1 ± 3.1 to 35.0 ± 6.4 ml/100 g/min, p < 0.0001) and ACZ reactivity (–0.02 ± 0.10 to 0.28 ± 0.21, p < 0.0001) of the MCA territory increased after EC-IC bypass compared with the baseline values. STA MFV was significantly correlated with the rCBF 14 days after EC-IC bypass (R = 0.70, p < 0.0001). A cutoff value of postsurgical STA MFV greater than 48.5 cm/s yielded the highest diagnostic accuracy (sensitivity 86%; specificity, 82%) for rCBF ≧32 ml/100 g/min after EC-IC bypass. Conclusions: STDU was available for evaluating postsurgical patency of the bypass flow and the rCBF of the ipsilateral MCA territory. The mean blood flow velocity of the operated STA is a highly sensitive parameter for predicting rCBF in the ipsilateral MCA territory after EC-IC bypass.