Venous consideration in petrosal approach: Microsurgical anatomy of the temporal bridging vein

OBJECTIVE: The technical difficulty of using the petrosal approach and the likelihood of encountering venous complications depend on the particular te mporal venous anatomy. To reduce such potential risks, neurosurgeons must h ave adequate knowledge of the variations in the anatomy of the temporal ven ous drainage system, particularly of the temporal bridging veins. METHODS: In 20 cadaveric specimens, the temporal bridging veins were examin ed with the aid of an operating microscope. The anatomic location of their termination and of the tributaries of these bridging veins was noted. RESULTS: Forty-four terminations and 109 tributaries of the temporal bridgi ng veins were identified in our specimens. The temporal bridging veins were divided into three groups according to the anatomic location of their term inations: 1) the transverse sinus group (seen in all 20 hemispheres), with drainage into the lateral part of the cerebellar tentorium, to which most o f the vein of Labbe belongs; 2) the tentorial group (seen in 50% of the 20 hemispheres), with drainage into the medial part of the tentorium, which is composed mainly of the middle and posterior temporobasal veins; and 3) the petrosal group (seen in 55% of the 20 hemispheres), with entry around the superior petrosal sinus, which may limit mobility of the temporal lobe in t he petrosal approach. On the basis of this anatomic information, we propose a new classification of the temporal venous drainage system and discuss th e clinical implications of these findings. CONCLUSION: In planning the petrosal approach, great care should be taken n ot only with the vein of Labbe but also with the petrosal bridging veins. K nowledge of this venous anatomy can reduce venous complications during the lateral cranial base approach.