Petro-occipital fissure

The petro-occipital or petroclival fissures, synchondroses, or sutures are the paired articulations between the lateral surface of the basilar part of the occipital bone (basiocciput, part of the clivus) and the posterior and medial surfaces of the petrous apex of the temporal bones. 

Terminology

Fissure is the most common term in the anatomical and radiological literature for this petro-occipital articulation ^1,2,5,8, but synchondrosis is sometimes used as well ^3,4,8. Both terms appear in the Terminologia Anatomica. Synchondrosis implies a primary cartilaginous joint (here part of the chondrocranium) that usually ossifies during development. However, this structure very slowly ossifies well into late adulthood and is not entirely cartilaginous in adults, but rather a mix of dense connective tissue and cartilage ⁴. The term petro-occipital suture thus also appears in the literature, implying a fibrous union, but this usage is less common ^1,6,7. "Fissure" may be preferable as a physical descriptor of a gap between bones, avoiding implications on the histological composition or developmental mechanism.

The term "petroclival" may be used synonymously with "petro-occipital" in adults in whom the spheno-occipital synchondrosis has ossified and formed the fused clivus.

Gross anatomy

It is a skull base landmark located in the anterior portion of the posterior cranial fossa.

Relations and boundaries

• anterior: foramen lacerum 
• medial: basilar part of the occipital bone
• lateral: petrous temporal bone
• posterior: jugular foramen 

Related pathology

The fissure is clinically important as it is often associated with skeletal myxoid chondrosarcomas of the skull base (~66% of cranial base chondrosarcomas) ⁵.