Sternocleidomastoid branches of occipital artery

The two sternocleidomastoid branches of the occipital artery (sternocleidomastoid artery) arise directly from the occipital artery and are the initial two branches of this artery. Uncommonly, the lower sternocleidomastoid branch can branch directly from the external carotid.

The lower sternocleidomastoid branch passes infero-external to the hypoglossal nerve before descending into the substance of the muscle to which its name is derived. The upper sternocleidomastoid branch diverts from the main trunk at the deep border of the proximal end of the posterior digastric muscle belly, coursing with the spinal accessory nerve prior to arborising into the sternocleidomastoid.

References

This article incorporates text in the public domain from page 556 of the 20th edition of Gray's Anatomy (1918)