Objective: The present anatomic study investigates alternative draining pathways of the petrosal vein territory, which allow compensation in case of surgical sacrifice.
Methods: In eight (four formaldehyde fixed and four alcohol fixed) specimens the petrosal vein complex has been dissected and studied. Three heads have been selectively injected via the superior petrous sinus with colored silicon in two different colors. Thereafter the posterior fossa content was removed epidurally from the skull and further fixed in 4% formaldehyde. The nervous and vascular structures were dissected under microscopic control, measured and photographed. 3D-photographs were elaborated.
Results: The petrosal vein was present in all cases and joined the superior petrous sinus always lateral to the trigeminal nerve as a single trunk. In the selectively injected specimens no passage of the colored silicon mixture to the contralateral venous brainstem territory could be discerned. However, the ipsilateral anastomoses to the deep supratentorial venous system--peduncular, anterolateral pontomesencephalic, lateral mesencephalic veins, and the tectal veins in connection with the pontotrigeminal vein--filled in all cases.
Conclusion: Although the present anatomical model does not reflect physiological aspects of vascular dynamics, we document an apparently compensatory venous blood drainage occurring via anastomotic pathways directed to the ipsilateral supratentorial venous system. These findings represent an interesting aspect for preoperative image-guided planning in cerebello-pontine angle surgery.