The anterior atlantooccipital membrane is a broad fibrous sheet connecting the anterior arch of the atlas to the anterior margin of the foramen magnum (basilar part of the occipital bone). It is continuous laterally with the articular capsules of the atlantooccipital joints and represents the superior continuation of the anterior longitudinal ligament at the craniocervical junction.
Reinforces the anterior atlantooccipital joint capsules, limits extension at the craniocervical junction, and together with the posterior atlantooccipital membrane forms the anterior and posterior walls of the atlantooccipital joint complex.
The anterior atlantooccipital membrane is assessed as part of craniocervical instability evaluation in patients with rheumatoid arthritis, trauma, and connective tissue disorders such as Ehlers-Danlos syndrome. Hyperextension injuries of the craniocervical junction can rupture this membrane, contributing to atlanto-occipital dislocation, a highly unstable and potentially fatal injury. Occipital condyle fractures may involve the attachment zone of this membrane.
Rupture of the anterior and posterior atlantooccipital membranes and the alar ligaments from extreme distraction-hyperextension forces produces craniocervical instability with risk of brainstem compression, high cervical cord injury, and death, managed with halo immobilisation and occipitocervical fusion.
