Flow capacity of a superficial temporal artery as a donor in a consecutive series of 100 patients with superficial temporal artery–middle cerebral artery bypass

OBJECTIVE A superficial temporal artery–middle cerebral artery (STA-MCA) bypass is classically considered a low-flow bypass. It is known that the flow in the flow augmentation STA-MCA bypass is influenced by flow demand of the revascularized territory and can reach significantly higher values. The authors report their intraoperative flow measurement data in a consecutive series of 100 STA-MCA bypasses performed at their institution. Moreover, in a subanalysis, they show the postoperative bypass flow measured with quantitative MR angiography (qMRA) noninvasive optimal vessel analysis (NOVA). METHODS Between January 2013 and October 2023, 100 patients with acute, subacute, or chronic large-vessel occlusion (LVO) or moyamoya disease underwent a flow augmentation STA-MCA bypass revascularization at the authors’ department with intraoperative bypass flow measurement. Patients with atherosclerotic LVO who underwent bypass surgery within a 6-week period following the onset of ischemic stroke symptoms were categorized into the acute bypass group, encompassing both acute and subacute LVO cases. Conversely, those who underwent bypass surgery > 6 weeks after the last occurrence of ischemic stroke were classified as the chronic group. Since May 2019, a consecutive subgroup of 37 patients received a postoperative (before discharge) bypass flow measurement with the qMRA-NOVA imaging tool. RESULTS The mean ± SD intraoperative bypass flow in this consecutive series of 100 STA-MCA bypasses was 53.5 ± 28.8 ml/min (range 14–145 ml/min). In the subanalysis, there was no difference in the intraoperative flow capacity between the acute and chronic groups and between the moyamoya and acute groups. Patients in the moyamoya group showed a significantly higher flow rate in the STA-MCA bypass compared with the chronic group (63.0 ± 30.2 ml/min vs 48.4 ± 26.5 ml/min, p = 0.03). In a consecutive subanalysis of 37 STA-MCA bypass cases, postoperative flow measurements were also performed using qMRA-NOVA, showing a significant increase in the flow of STA-MCA bypasses after surgery compared with intraoperative flow measurements (mean intraoperative bypass flow rate vs qMRA-NOVA postoperative bypass flow rate: 73.4 ± 29.9 ml/min vs 111.3 ± 51.4 ml/min, p = 0.005). CONCLUSIONS Using intraoperative and postoperative quantitative flow measurements of the STA, the data confirm that the flow in the flow augmentation STA-MCA bypass is influenced by the flow demand of the revascularized territory and can reach high values if needed. Moreover, the significant flow increase in the postoperative flow measurement using qMRA-NOVA demonstrates that the bypass can increase its flow over time.