Anatomy of the suboccipital region

You may think of the suboccipital region as just ‘the back of the head.’ However, there’s more to it than meets the eye! This region is home to several muscles that assist in various head and neck movements, as well as the vessels and nerves that nourish them.

The suboccipital region is actually a pyramid shaped muscle compartment located inferior to the external occipital protuberance and deep to the superior part of the posterior cervical region, underlying the trapezius, sternocleidomastoid, splenius, and semispinalis capitis muscles.

This region has four small paired muscles of which three of them form the boundaries of an area known as the suboccipital triangle.

Superomedially, the suboccipital triangle is bounded by the rectus capitis posterior major muscle; superolaterally by the obliquus capitis superior muscle and inferolaterally by the obliquus capitis inferior muscle.

The floor of the suboccipital triangle is formed by the posterior atlanto-occipital membrane and the posterior arch of the atlas, while its roof is formed by the semispinalis capitis muscle. The main inhabitants of the suboccipital triangle are the vertebral artery and the suboccipital nerve.

Now, let’s take a closer look at the muscles of the suboccipital region. There are four suboccipital muscles which lie deep to the semispinalis capitis muscle.

First, there’s the rectus capitis posterior major, which originates on the spinous process of the axis or C2 vertebra and inserts on the lateral part of the inferior nuchal line of the occipital bone.

Second, there’s the rectus capitis posterior minor muscle, which originates on the posterior tubercle of the posterior arch of the atlas or C1 vertebra. Then it goes on to insert on the medial part of the inferior nuchal line of the occipital bone.

Third, there’s the obliquus capitis inferior, which originates on the spinous process of the axis - or C2 and inserts on the transverse process of the atlas.

And finally, the obliquus capitis superior originates on the transverse process of the atlas and inserts on the occipital bone, between the superior and inferior nuchal lines.

All four muscles are supplied by the suboccipital nerve and the vertebral artery, which lie in the central part of the suboccipital triangle.

The main function of these muscles is maintaining the posture of the head, but they also assist in movements such as extension, lateral flexion and rotation of the atlanto-axial joints.

Now, let’s look at the nerves that provide innervation to the suboccipital muscles and the skin of the posterior cervical region. First, there’s the suboccipital nerve, which is actually the posterior ramus of the C1 spinal nerve.

From its origin, the suboccipital nerve travels between the cranium and the atlas until it courses within the suboccipital region alongside the vertebral artery. One thing to remember is that this nerve innervates the suboccipital muscles, but not any of the overlying skin.