Posterior atlanto-occipital membrane

The posterior atlanto-occipital membrane attaches the anterosuperior border of the posterior arch of the atlas (C1) to the posterior margin of the foramen magnum. It lies immediately posterior to the spinal theca and is continuous inferiorly with the ligamentum flavum (sometimes referred to at C1/2 as the posterior atlanto-axial membrane) and ligamentum nuchae posteriorly.

Posterior to it lies the suboccipital muscles. The atlantic (V3) portion of the vertebral artery runs anteriorly to pierce the membrane and dura and become the dural (V4) portion.