The suboccipital muscles are a group of four muscles situated underneath the occipital bone. All the muscles in this group are innervated by the suboccipital nerve.
They are located within the suboccipital compartment of the neck; deep to the sternocleidomastoid, trapezius, splenius and semispinalis muscles. They collectively act to extend and rotate the head.
In this article, we shall look at the anatomy of the suboccipital muscles – their attachments, actions and innervation.
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Rectus Capitis Posterior Major
The rectus capitis posterior major is the larger of the rectus capitis muscles. It is located laterally to the rectus capitis posterior minor.
- Attachments: Originates from the spinous process of the C2 vertebrae (axis) and inserts into the lateral part of the inferior nuchal line of the occipital bone.
- Actions: Extension and rotation of the head.
- Innervation: Suboccipital nerve (posterior ramus of C1).
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Rectus Capitis Posterior Minor
The rectus capitis posterior minor is the most medial of the suboccipital muscles. There is a connective tissue bridge between this muscle and the dura mater (outer membrane of the meninges) – which may play a role in cervicogenic headaches.
- Attachments: Originates from the posterior tubercle (a rudimentary spinous process) of the C1 vertebra. Attaches to the medial part of the inferior nuchal line of the occipital bone.
- Actions: Extension of the head.
- Innervation: Suboccipital nerve (posterior ramus of C1).
Fig 1
The left occipital muscles, which lie underneath the deep muscles of the back.
Obliquus Capitis Inferior
The obliquus capitis inferior is the most inferiorly positioned of the suboccipital muscles. It is the only muscle within this group which has no attachment to the cranium.
- Attachments: Originates from the spinous process of the C2 vertebra and attaches onto the transverse process of C1.
- Actions: Extension and rotation of the head.
- Innervation: Suboccipital nerve (posterior ramus of C1)
Obliquus Capitis Superior
The obliquus capitis superior is located laterally in the suboccipital compartment.
- Attachments: Originates from the transverse process of C1 and attaches onto the occipital bone (between the superior and inferior nuchal lines).
- Actions: Extension of the head.
- Innervation: Suboccipital nerve (posterior ramus of C1)
Suboccipital Triangle
The suboccipital triangle is an area bordered by three of the suboccipital muscles. It contains the vertebral artery (can be identified during surgery), suboccipital venous plexus and suboccipital nerve. Its borders are as follows:
- Superomedial: Rectus capitus posterior major
- Superolateral: Obliquus capitus superior
- Inferior: Obliquus capitus inferior
- Floor: Posterior atlanto-occipital membrane and posterior arch of the C1 vertebrae (atlas)
- Roof: Semispinalis capitus
Fig 2
The suboccipital triangle. It can be used to locate the vertebral artery, as shown on this illustration.