The posterior atlantooccipital membrane is a broad, thin fibrous structure that connects the posterior arch of the atlas (C1) to the occipital bone along the posterior margin of the foramen magnum. It lies posterior to the atlantooccipital joint, contributing to the stability of the craniovertebral junction alongside the anterior atlantooccipital membrane.

Laterally, the posterior atlantooccipital membrane blends with the capsules of the atlantooccipital joints. Anterior to the membrane are the structures of the vertebral canal, while posterior to it lie the suboccipital muscles and the nuchal ligament.

Although the posterior atlantooccipital membrane is traditionally described as a distinct structure, some recent studies suggest that it may not always be clearly demarcated from the surrounding structures. There are also claims that it may not attach directly to the posterior arch of the atlas (C1). Some authors even question the existence of this membrane. While the exact anatomical variations of the posterior atlantooccipital membrane remain a subject of investigation, we show it as described in traditional anatomical textbooks.

A notable feature of this membrane is its relationship with the groove for the vertebral artery that is located on the posterior arch of the atlas (C1). The posterior atlantooccipital membrane forms an arch above the groove. This defect allows the vertebral artery to pass through the groove without being obstructed.

Functionally, the posterior atlantooccipital membrane helps limit excessive extension of the head and neck, contributing to the overall flexibility and stability of the cervical spine. It also forms a protective barrier for the spinal cord and surrounding structures at the craniovertebral level. However, its precise functional significance and role in craniovertebral stability remains an area of ongoing research.

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Posterior atlantooccipital membrane