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Exocranial Perspective of Posterior Skull Base

Surgical Correlation


Inferior view of posterior half of the skull. The foramen magnum is the largest of the cranial foramina. Along its anterolateral margin are the occipital condyles for articulation with the atlas (atlanto-occipital joint). Posterior to the condyles are the condylar canals, emissary foramina for emissary veins connecting the sigmoid sinus to the occipital vein as well as transmitting meningeal branches of the occipital artery. Lateral to these are mastoid foramina, also emissary foramina. They are most commonly located near the posterior margin of the mastoid process, near or within the occipitomastoid suture, or in the occipital bone. They are variable in number and size and transmit emissary veins connecting to the sigmoid sinus and a small dural branch of the occipital artery. Anterior and lateral to the occipital condyles are the opening of the jugular foramen and carotid canal. Between the styloid and mastoid processes are the stylomastoid foramina for exit of the facial nerve. Anterior to the foramen magnum is the clivus, which bears a small midline elevation for attachment of the fibrous raphe of the pharynx. At the junction of the petrous apex and the body and greater wing of the sphenoid is a space, the foramen lacerum, filled in life by fibrous cartilage. Within the greater wings of the sphenoid are the foramen ovale and spinosum. Lateral to the foramen spinosum is the mandibular fossa, which is bounded anteriorly by the articular tubercle. The fossa receives the mandibular condyle for the temporomandibular articulation. (Image courtesy of AL Rhoton, Jr.)