Fig. 41.1 Origin from the subclavian artery on the top of the arch, near the thyrocervical trunk (right side 90%; left side 90%). Schematic.

Fig. 41.2 Origin from the subclavian artery further medial, more than 2 cm from the thyrocervical trunk; on the right side, often from the bifurcation of the brachiocephalic trunk (right side 4%; left side 3%). Schematic.

Fig. 41.3 Origin from the subclavian artery lateral to the thyrocervical trunk (right side 4%; left side <0.1%). Schematic.

Fig. 41.4 Common origin with the thyrocervical trunk (right side <1%; left side 2%). Schematic.

Fig. 41.5 Origin from the aortic arch (right side <0.1%; left side 4%). For different subtypes, see Figs.2.12–2.19. Schematic (a) and X-ray angiography, anterior view, left subclavian artery injection (b); because the catheter slipped out of the subclavian artery, the second frame looks like an aortic arch injection; finally the tip of the catheter is inside the origin of the left vertebral artery, which originates directly from the aortic arch.