Occipital bone

Function

Forms the posteroinferior cranium and the foramen magnum through which the brainstem becomes the spinal cord. Its condyles articulate with the atlas for the nodding 'yes' movement, and its nuchal lines anchor the postural neck and back muscles.

Landmarks

• Foramen magnum
• Occipital condyles
• External occipital protuberance (inion)
• Superior and inferior nuchal lines
• Hypoglossal canal
• Internal occipital crest

Articulations (joints)

• Parietal bones (lambdoid sutures)
• Temporal bones
• Sphenoid bone
• Atlas (C1) at the occipital condyles

Clinical relevance

Atlanto-occipital dislocation from high-energy trauma is usually fatal. The hypoglossal canal transmits cranial nerve XII — basal occipital fractures can paralyse the tongue.