Identification of venous variants in the pineal region with three-dimensional preoperative magnetic resonance imaging navigation in patients harbouring tumors in this area: significance for surgical approach to the lesion.

OBJECT: The purpose of this study was to identify the anatomy of pineal region venous complex using neuronavigation software when distorted by the presence of a space-occupying lesion and to describe the anatomical relationship between lesion and veins. Moreover we discuss its influence on the choice of the surgical strategy.

METHODS: Of the 33 patients treated at our Institute for pineal region tumors between 2003 and 2008 we used the neuronavigation software to depict the venous system of the pineal region in 14 patients. We focused on depiction of the basal vein of Rosenthal (BV), the internal cerebral vein (ICV) and the vein of Galen: connection patterns between the veins and the type of anatomical distortion caused by the lesion were investigated and classified.

RESULTS: Using the neuronavigation software for three-dimensional (3D) reconstruction of MRI images the ICV was clearly depicted in all patients on both sides (100%). Last segment of the BV was identified in 25 sides on a total of 28 (89.3%) and absent in 3 of the 28 sides (10.7%). Studying the distortion effect of the tumor on the galenic venous system, three directions of displacement were observed: craniocaudal, anteroposterior and lateral. Seven patients presented a cranial dislocation, 5 patients caudal dislocation and there was no craniocaudal shift in 2 patients. Considering the anteroposterior displacement: 3 subjects showed an anterior shift of the veins, 5 subjects posterior shift and no anterioposterior shift was present in 6 patients. Only 2 of the 14 patients presented lateral displacement of the veins. The principal approaches used in this series were: supracerebellar infratentorial and interhemispheric parieto-occipital. The craniocaudal displacement of the pineal veins seems to be the most important for the choice of the approach.

CONCLUSION: The galenic venous system has a central role in the surgery pineal region tumors. Our study demonstrates that the architecture of the pineal veins and their anatomical relationship with the lesion can be depicted with great accuracy by using 3D neuronavigation software in order to facilitate surgical planning and intraoperative orientation.