The dural venous sinuses: normal intraluminal architecture defined on contrast-enhanced MR venography.

Introduction: Our objective was to define the appearance and distribution of normally occurring intraluminal structures within the dural venous sinuses on contrast-enhanced MR venography (CE-MRV).
Methods: Informed consent was obtained from all subjects participating in the study, and the study protocol was approved by the institutional review board of the University Health Network. A group of 56 patients underwent CE-MRV. Intraluminal structures were categorized as an arachnoid granulation (AG) or trabeculation (Willis cord). Willis cords within the transverse and sigmoid sinuses as well as AGs 4 mm or more in size were recorded.
Results: In 20 of the 56 patients (36%), 29 AGs measuring 4 mm or more were identified within the dural sinuses. All AGs were spherical or ovoid and occurred at sites where a cortical vein joined a dural sinus. Nearly all AGs (28 of 29, 97%) displayed an eccentric internal vein. Willis cords were seen within the superior sagittal sinus in all patients. Willis cords were less prevalent in the remaining dural sinuses. A minimum of one Willis cord was seen in 58 of the 112 transverse sinuses (52%). These cords were 1-2 mm in maximal thickness, uniformly smooth, and commonly partitioned the sinus. Willis cords and AGs (of any size) were not encountered within the sigmoid sinuses or jugular veins.
Conclusion: CE-MRV elucidates structures normally found within the dural sinuses. These consist of AGs and Willis cords. This report confirms and establishes new criteria for identification of these normally occurring intraluminal structures providing a basis for their differentiation from pathologic entities.