A rare case of positional vertebrobasilar ischemia with the retrograde flow of the vertebral artery

Positional vertebrobasilar ischemia, also known as Bow hunter stroke, is typically caused by mechanical compression of the vertebral artery (VA). On the other hand, subclavian steal syndrome is incidentally detected by vertigo, syncope or loss of consciousness due to the steal phenomenon. A 61-year-old man suffered from near syncope when he turned his head to the left side. Although asymmetric arm blood pressure of the right dominant was observed, arm claudication was not detected. Computed tomographic angiography and magnetic resonance imaging revealed total occlusion of the left subclavian artery, hypoplasia of the right VA and an incomplete circle of Willis. Furthermore, carotid Doppler ultrasonic echography revealed retrograde blood flow of the left VA. It means that head rotation might occur in the left VA ischemia. An axillary-axillary bypass surgery was performed and ultrasonic echography showed anterograde effective blood flow of the left VA after the procedure.