[1][2] The left superior intercostal vein drains the 2nd and 3rd posterior intercostal veins on the left side of the body.

It usually drains into the left brachiocephalic vein.

[1][2] It may also communicate with the accessory hemiazygos vein.

[2] As it passes posteriorly above the aortic arch, it crosses deep to the phrenic nerve and the pericardiacophrenic vessels and then superficial to the vagus nerve.

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