White arrow points to the primitive trigeminal artery (A–D). MRI, fluid-attenuated inversion recovery sequence, demonstrating the left ventral pontine infarction (A). Magnetic resonance angiography demonstrates proximal hypoplastic-stenotic vertebrobasilar system (B). Selective left internal carotid artery angiogram: lateral (C) and anteroposterior view (D) (same viewing angle as in B). Triangular arrowhead points to the left internal carotid artery (B–D).