To evaluate cerebral hemodynamics before and after unilateral internal carotid artery occlusion in patients undergoing superficial temporal artery-middle cerebral artery bypass (STA-MCA bypass) by transcranial Doppler ultrasound (TCD) and CT perfusion imaging (CTP).

Eighty-five patients who underwent STA-MCA bypass grafting for unilateral internal carotid artery occlusion at the Neurosurgery Department of the First Affiliated Hospital of Soochow University from January 2016 to May 2021 were retrospectively enrolled. According to the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) criteria, the patients were divided into group A (65 cases; ASITN/SIR Grade 0-2) and group B (20 cases; ASITN/SIR Grade 3). The average blood flow velocity (Vm), peak systolic blood flow velocity (Vs), end-diastolic blood flow velocity (Vd), and vascular pulse index (PI) of the bilateral middle cerebral arteries (MCA) in the distal section (detection depth 30~40 cm) were evaluated by TCD before and after STA-MCA bypass. CTP parameters of the bilateral basal ganglia and temporal lobes were evaluated to calculate cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and peak time (TTP), as well as CTP of the affected side/healthy side (rCTP). The National Institutes of Health Stroke Scale (NIHSS) was used to evaluate the neurological score. Spearman rank correlation was used to analyze the correlation between the Vm of the MCA distal segment and NHISS score.

The Vm, Vs, Vd, and PI of the MCA distal segment on the affected side were lower than those on the healthy side in both groups A and B before and after surgery (P<0.05 for all). Preoperative Vm, Vs, Vd, and PI of the affected side in group A were lower than those in group B, and postoperative Vm, Vs, Vd, and PI of the two groups were significantly higher than those before surgery (P<0.05 for all). There were no significant differences in Vm, Vs, Vd, or PI between the two groups after surgery (P>0.05 for all). Before operation, rCBF and rCBV in group A were lower than those in group B, and rMTT and rTTP were higher than those in group B (P<0.05 for all). rCBF after operation was higher than that before operation, while rMTT and rTTP were lower than those before operation (P<0.05 for all).The postoperative rCBV of group B was lower than that before surgery (P<0.05), the postoperative rCBV of the temporal lobes in group A was higher than that before surgery (P<0.05), and the rCBV of the basal ganglia was not significantly different from that before surgery (P>0.05). Preoperative and postoperative NHISS scores in group A were significantly higher than those in group B, (P<0.05 for both). The NHISS scores of the two groups were significantly lower after surgery than before surgery (P<0.05 for both). There was a negative correlation between MCA Vm and NHISS score in both groups before surgery (r=-0.659, P<0.01; r=-0.626, P<0.01), while there was no linear correlation between MCA Vm and NHISS score after surgery.

After STA-MCA bypass surgery, cerebral perfusion is significantly improved. TCD and CTP are helpful to evaluate the perioperative cerebral hemodynamics of STA-MCA bypass, and TCD is an effective tool for non-invasive clinical evaluation and follow-up of cerebral hemodynamics.