Anterior atlantooccipital membrane

The anterior atlantooccipital membrane is a broad and dense sheet of fibrous tissue that connects the upper aspect of the anterior arch of the atlas (C1) to the occipital bone of the skull along the anterior margin of the foramen magnum. Laterally, it blends with the capsules of the atlantooccipital joints, thickening them anteromedially.

The membrane lies anterior to the atlantooccipital joints, forming a barrier that helps protect the delicate structures surrounding the joints. Anterior to the membrane are the longus capitis muscles and rectus capitis anterior muscles from the prevertebral muscle group. Posterior to the membrane are the alar ligaments.

Although the anterior longitudinal ligament is a distinct structure that extends up to the occipital bone, some authors consider the anterior atlantooccipital membrane a continuation of the anterior longitudinal ligament above the C1 level. The anterior atlantooccipital membrane is narrower than the posterior atlantooccipital membrane, but it is more durable.

The anterior atlantooccipital membrane forms part of the supportive structure of the atlantooccipital joint, providing support and stability to the region where the skull meets the cervical spine. It plays a crucial role in limiting excessive extension of the head and neck, contributing to the overall movement control of the cervical spine.