Abstract: Objective To summarize the characteristics of hemodynamic changes in vertebral artery system and carotid artery system caused by innominate artery(IA)steno-occlusion, and to make differential diagnosis. Methods The results of transcranial Doppler ultrasonography(TCD)and spectral characteristics of vertebral artery system and carotid artery system steal in two patients with extreme IA steno-occlusion were analyzed. Relevant literature was reviewed. Results Case 1 was a 77-year-old male whose right upper extremity systolic blood pressure was 51 mmHg lower than the other side. Before general anesthesia, TCD showed extreme steno-occlusion of IA and two steal pathways, including basilar artery(BA)→ vertebral artery(VA), and left anterior cerebral artery(ACA)→ right ACA→ terminal internal carotid artery(TICA)→ right common carotid artery(CCA). CTA demonstrated a dissection and extreme narrowing in the IA. Case 2 was a 76-year-old female whose lower right upper extremity systolic blood pressure was 34 mmHg lower than the other side. TCD revealed extreme steno-occlusion of IA and two steal pathways, including left vertebral artery(LVA)→right vertebral artery(RVA), and left arteriae cerebri anterior(LACA)→right arteriae cerebri anterior(RACA )→right middle cerebral artery(RMCA). Carotid MRA suggested occlusion in IA. Conclusion IA steno-occlusion may cause bilateral cerebrovascular pressure imbalance and lead to the occurrence of steal. TCD can be sensitive to detect the steal pathways. When RCCA shows low and round, or steal spectrum, or there is no blood flow signal, and when RVA shows steal spectrum, extreme IA steno-occlusion should be suspected.

Key words: Stenosis of the innominate artery, Occlusion of the innominate artery, Steal phenomenon, Steal pathways, Transcranial Doppler ultrasonography