They are arteriovenous shunts located in the dura that usually involve large dural venous sinuses.

Arterial supply is usually through meningeal branches of the external carotid, internal carotid, and vertebral arteries. Drainage is via dural venous sinuses or other dural or leptomeningeal channels.

Conclusion MR is an effective technique for measuring the blood flow in transverse sinuses, which can reflect the venous drainage dominance from the point of "quantity" view.