The tectorial membrane is the upward continuation of the posterior longitudinal ligament from C2 into the skull, spanning the posterior surface of the dens and the atlantoaxial articulation to attach at the foramen magnum anteriorly. It is the deepest layer of the atlantoaxial ligament complex and limits skull-atlas flexion. Its disruption in basilar skull fractures or severe atlantoaxial injuries contributes to craniocervical instability.
| Origin | Posterior surface of the C2 body and dens |
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| Insertion | Anterior surface of the foramen magnum (basion) — the upward continuation of the posterior longitudinal ligament |
| Actions | Limits flexion of the atlantoaxial joint; restrains anterior translation of the skull on the atlas |
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The tectorial membrane is assessed on sagittal MRI at the craniocervical junction, where disruption appears as loss of the normal dark (dark on all sequences) fibrous band at the posterior dens level. It is one of four key ligaments (alongside transverse, alar, and apical) assessed in craniocervical junction injury protocols.
Tectorial membrane disruption contributing to craniocervical instability in high-energy cervical trauma requiring occipitocervical fusion.
