Classification of the Superior Petrosal Veins and Sinus Based on Drainage Pattern

The increasing number of reports of complications after sacrificing the superior petrosal veins, the largest veins in the posterior fossa, has led to a need for an increased understanding of the anatomy of these veins and the superior petrosal sinus into which they empty.To examine the anatomy of the superior petrosal veins and their size, draining area, and tributaries, as well as the anatomic variations of the superior petrosal sinus.Injected cadaveric cerebellopontine angles and 3-dimensional multifusion angiography images were examined.The 4 groups of the superior petrosal veins based on their tributaries, course, and draining areas are the petrosal, posterior mesencephalic, anterior pontomesencephalic, and tentorial groups. The largest group was the petrosal group. Its largest tributary, the vein of the cerebellopontine fissure, was usually identifiable in the suprafloccular cistern located above the flocculus on the lateral surface of the middle cerebellar peduncle. The medial or lateral segment of the superior petrosal sinus was absent in 40% of cerebellopontine angles studied with venography.The superior petrosal veins and their largest tributaries, especially the vein of the cerebellopontine fissure, should be preserved if possible. Obliteration of superior petrosal sinuses in which either the lateral or medial portion is absent may result in loss of the drainage pathway of the superior petrosal veins. Preoperative assessment of the superior petrosal sinus should be considered before transpetrosal surgery in which the superior petrosal sinus may be obliterated.