Prominent Lateral Tentorial Venous Sinuses

TENTORIAL SINUSES

Numerous tentorial sinuses drain near the confluence / torcula herophili. These venous channels may provide significant drainage for adjacent cerebellum. They can be enlarged significantly if the straight sinus or superior sagittal sinus is occluded.

Image from Diagnostic Neuroradiology, Osborn, 1994, showing prominent tentorial sinuses, a normal finding.

Tentorial sinuses have been divided into medial and lateral groups.

Medial tentorial sinuses drain the superior surface of the cerebellum and they empty into the Straight Sinus and Transverse sinus confluence.

Lateral tentorial sinuses are formed by the covergence of veins draining the basal and lateral surfaces of temporo-occipital lobes. These drain into the transverse-sigmoid junction and anterior two thirds of transverse sinus on each side.

The veins emptying into the lateral tentorial sinuses can again be divided into medial and lateral branches.

Diagramatic depiction of the lateral and medial branches of Lateral Tentorial sinuses, AJNR 2004.

Lateral tentorial sinuses are again divided into type I (venous candelabra), II (multiple independent veins) and III (venous lakes within tentorium) based on the venous configuration.

Present case depicts a Type I Lateral tentorial sinus with Vein of Labbe draining into it. In type I LTS the draining veins from a single trunk. 

Details regarding lateral tentorial sinuses are well elucidated in reference 2.

References:
1) Diagnostic Neuroradiology, Osborn, 1994.
2) AJNR Am J Neuroradiol. 2004 Aug;25(7):1181-8. Delineation of lateral tentorial sinus with contrast-enhanced MR imaging and its surgical implications. Miabi Z1, Midia R, Rohrer SE, Hoeffner EG, Vandorpe R, Berk CM, Midia M.