The Anatomy of the Occipital Artery

The occipital artery is part of the occipital area of the skull. It is located within the solid connective tissue of the occipital bone. It is one of the posterior branches of the external carotid artery opposite the facial artery. The external carotid artery is a major artery of the head and neck supplying blood to the face and neck, while the occipital artery supplies blood to the back of the scalp, the sternomastoid muscles, and the deep muscles of the neck and back.

Anatomy

The occipital artery passes just behind the back of the digastric muscle, a small muscle located just below the jaw. The occipital artery then crosses the carotid artery, the internal jugular vein, the hypoglossal, vagus nerve, and accessory nerve.

The internal jugular vein collects blood from the brain to the superficial parts of the face and neck. The hypoglossal nerve is the twelfth cranial (skull) nerve and is responsible for motor function.

The vagus nerve is the longest of all the cranial nerves and controls the parasympathetic nerve center where all the communicating motor functions and impulses take place and move to every organ of the body. Last, the accessory nerve (the eleventh cranial nerve) supplies some of the muscles in the neck and shoulders.

Location

The occipital artery rises between the transverse process of the atlas located in the neck and the mastoid process located in the back part of the temporal bone, situated just behind the ear. The temporal bones are found at the sides (temples) and bones of the skull. They also house the structures of the ears. The mastoid process is an attachment to some of the neck muscles.

The occipital artery eventually reaches the side border of the rectus capitis lateralis, a paired muscle of the upper neck just below the back of the head on each side. These muscles help control lateral flexion, the movement needed for tilting the end to either side.

After passing the rectus capitis lateralis, the occipital artery passes the occipital grove of the temporal bone. This part of the temporal bone is covered by many important muscles, including the sternocleidomastoid—the muscle located at the base of the skull on either side of the neck that assists with neck movement—and the splenius capitis, the broad strap-like muscle in the back of the neck.

The occipital artery will then change its course, turning upward into the deep cervical fascia located in the neck, and then goes up into the dense superficial fascia of the scalp. Once in the scalp, it divides into branches to supply the skin at the back of the scalp.

Structure

The occipital artery consists of two main branches: the upper and lower branches. The upper branch passes the accessory nerve descending into the deep part of the sternocleidomastoid. The lower branch is at the beginning part of the occipital artery, descending backwards into the sternocleidomastoid.

The occipital artery also connects to the mastoid branch of the temporal bone entering into the rear part of the cranial fossa—the depressions located in floor of the cranial cavity—through the mastoid foreman, the hole in the back of the temporal bone, to supply the dura mater—the tough outside membrane covering the brain and spinal cord.

Function

The main function of the occipital artery is to supply oxygenated blood to the muscles of the upper neck and scalp, but it is not its only function. In fact, the occipital artery is responsible for more than the occipital area as it has several branches, in addition to the upper and lower ones.

• The muscular branches supply the digastric below the jaw and longus capitis, a pre-vertebral muscle in the neck.
• The auricular branch supplies blood to the back of the ears.
• The meningeal branch supplies the dura mater of the posterior cranial fossa.
• The sternocleidomastoid branch divides the upper and lower branches.
• The descending branch is the largest of all the branches of the occipital artery starting in the back of the neck and dividing into two parts: one that supplies the trapezius muscle (the large muscle bundle extending from the back of the head and neck to the shoulder) and another part connecting to the vertebral artery (an artery of the neck that is a major source of blood to the brain).

Clinical Significance

While the occipital artery plays an important part in providing blood supply to different parts of the head, neck, skull, and face, it is rarely reported in medical literature as being related to any health condition or as being the cause of one. However, there are cases of aneurysms related to the occipital artery, and on its significance in surgical procedures of the skull.

Aneurysms

Aneurysms of the occipital artery are very uncommon and of the cases that do exist, they tend to be consequences of infection, autoimmune disease, or trauma—blunt force, penetrating, or surgical. However, there have been a handful of cases that were not the result of trauma but the majority of these are pseudo-aneurysms—false aneurysms where blood collects in the outer layers of an artery.

A 2018 article in the International Journal of Surgery Case Reports reported on the case of an aneurysm of the occipital artery where the patient reported discomfort and tongue problems that were eventually noted to be caused by compression on the hypoglossal nerve. The aneurysm was surgically treated, and the patient was no longer experiencing symptoms.

In 2017, Surgical Neurology International reported on a case of a giant pseudo-aneurysm of the occipital artery. The case involved a 76-year-old patient with a giant occipital artery pseudo-aneurysm that was likely the result of a head injury he had sustained a month earlier. The pseudo-aneurysm was surgically removed and the patient fully recovered.

The Journal of Medical Case Reports in 2014 reported on the case of a 14-year-old boy who had a painful scalp mass resulting from a basketball strike to the head four months prior. The pain had subsided days after the trauma, but the mass continued for months. After examination and imaging, the patient was found to have a thrombosed (clotted) traumatic aneurysm of the occipital artery. The mass was surgically removed, and the child did not have any recurrence.

Medical Research

The occipital arteries of cadavers have been harvested for use in posterior fossa bypass surgery to treat tumors. The posterior fossa is a small space in the skull, found near the brainstem and cerebellum.

A 2014 article in the journal World Neurosurgery reported on the importance of properly harvesting the occipital artery to be used for posterior fossa revascularization where blood flow needs to be properly restored. Researchers noted that detailed knowledge of the occipital artery is helpful in dissecting the artery for intracranial bypasses and for avoiding disastrous complications.