Cut Section of the Skull Displaying the Occipital Sinus

Description

Sectioned cranial vault exposes the midline dural venous system, with the occipital sinus coursing in the attached margin of the falx cerebelli along the internal occipital crest, posterior to the foramen magnum. Superiorly it approaches the confluence of sinuses (torcular Herophili), where it relates to the posterior end of the superior sagittal sinus and the origins of the transverse sinuses running laterally along the tentorium cerebelli. Inferiorly, venous channels converge toward the marginal sinus that encircles the foramen magnum and continues to the sigmoid sinus and internal jugular vein. Inner tables of the occipital and parietal bones frame these relationships. Occipital sinus anatomy matters because it is variable, frequently small, and easy to overlook until it bleeds. Posterior fossa and foramen magnum approaches (suboccipital craniotomy, midline posterior fossa decompression, and some Chiari I procedures) cross the internal occipital crest and can open the occipital or marginal sinus, creating brisk venous hemorrhage and a difficult dural closure. This cut section also clarifies how venous drainage can reroute when dominant transverse or sigmoid sinuses are hypoplastic, a point that influences preoperative planning and interpretation of MR venography. Neuroanatomy and neurosurgery teaching sets use this view to explain dural folds and their sinuses as fixed, surgically relevant landmarks rather than free veins. It also suits atlas figures and review articles discussing posterior fossa venous variants, torcular asymmetry, and procedural risk around the foramen magnum. Anatomical accuracy verified by SciePro's Medical Advisory Board.