Microsurgical anatomy of the venous drainage of the mesencephalodiencephalic junction

OBJECTIVE: The veins draining the posterior wall of the third ventricle and its adjacent structures and the posterior part of the midbrain have been the most neglected of the intracranial vascular structures in both the anatomic and neurosurgical literature. During our dissections of the pineal region and the quadrigeminal cistern, we did not always encounter topographic anatomy as described in previous articles. The purpose of this study is to describe the topographic anatomy and normal variations of the specific veins that drain the collicular plate and the pineal body and their adjacent structures with a view to better defining neurosurgical approaches to the pineal region. METHODS: The deep cerebral veins draining the pineal body, the collicular plate, and their surrounding neural structures were examined on both sides of 25 adult cadaveric brains. In all specimens, the carotid and vertebral arteries and the jugular veins were perfused with red or blue silicone, respectively, to facilitate dissection under X 3 to X 40 magnification. RESULTS: The venous plexus on the dorsal aspect of the collicular plate drains via collicular veins according to three different patterns. These types of drainage are closely related to the existence or absence of the basal vein on one or both sides. CONCLUSION: The veins draining the superior and inferior aspects of the pineal body form a superior and an inferior pineal vein that usually drain into the internal or great cerebral vein.