The marginal sinus is a dural venous sinus surrounding the margin of the

foramen magnum The foramen magnum () is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblongata, passes thro ...

inside the skull, accommodated by the groove for marginal sinus. It usually drains into either the

sigmoid sinus The sigmoid sinuses (sigma- or s-shaped hollow curve), also known as the , are paired dural venous sinuses within the skull that receive blood from posterior transverse sinuses. Structure The sigmoid sinus is a dural venous sinus situated withi ...

, or the jugular bulb. It communicates with the basilar venous plexus anteriorly, and the

occipital sinus The occipital sinus is the smallest of the dural venous sinuses. It is usually unpaired, and is sometimes altogether absent. It is situated in the attached margin of the falx cerebelli. It commences near the foramen magnum, and ends by draining in ...

posteriorly (the posterior union of the left and the right marginal sinus usually representing the commencement of the occipital sinus); it may form extracranial communications with the

internal vertebral venous plexuses The internal vertebral venous plexuses (intraspinal veins) lie within the vertebral canal in the epidural space, embedded within epidural fat. They receive tributaries from bones, red bone marrow, and spinal cord. They are arranged into four interc ...

, or deep cervical veins.

Clinical significance

Arteriovenous fistulas involving the marginal sinus have been described - often following basilar skull fractures. The marginal sinus must be traversed during surgical entry into subdural space deep to the foramen magnum.

References

{{Portal bar, Anatomy Veins of the head and neck Anatomy Human anatomy