The Posterior Atlantooccipital Membrane: The Anchor for the Myodural Bridge and Meningovertebral Structures

Introduction: Sheet plastination has provided evidence that the posterior atlantooccipital membrane attaches to the dura's posterior sleeve at the cerebrospinal junction. These findings contradict the traditional anatomical description of this membrane extending from the atlas' posterior arch to the foramen magnum. Methods: A total of 16 plastinated cadavers were studied to evaluate the in situ and gross configuration of the posterior atlantooccipital membrane. Fifteen cadavers underwent sheet plastination, and one head was hemisected and plastinated. In all specimens, stereomicroscopy was used to evaluate the posterior atlantooccipital membrane and related structures within the intervertebral and epidural spaces. Results: In all 16 specimens, the posterior atlantooccipital membrane extending from the occiput, merged with the craniocervical dura mater, and formed a membrane-dura complex that ended at the level of the third cervical vertebra. The superior and inferior myodural bridge coalesced with their respective vertebrodural ligaments and fused with the posterior atlantooccipital membrane at their respective interspaces. Conclusion: The median aspect of the posterior atlantooccipital membrane does not directly communicate with the posterior arch of the atlas. Instead, the posterior atlantooccipital membrane converges with the craniocervical dura mater and terminates at the level of the third cervical vertebra. This membrane-dura complex serves as a common attachment site for the myodural and vertebrodural structures.