A-9. Angiographic Changes of the Veins of the Posterior Cranial Fossa in the Cerebellopontine Angle Tumors

Introduction: Displacement of the cerebellar arteries of the cerebellopontine angle tumor is well known and have been reported by many authors.Little attention have been paid, however, to the venous changes of the posterior cranial fossa.We have studied the topographic anatomy of the venous system of the posterior cranial fossa and reported the phlebographic signs of the cerebellopontine angle tumors.Materials and Methods: For the study of the topographic anatomy, polyester plastic models of the veins of the posterior cranial fossa were made, using the cadavers ten to forty hours after death.Both carotid and vertebral ateries were canulated and flushed with two to three liters of physiological saline.The bilateral internal jugular veins were then canulated, and one and a half liters of polyester plastic, colored blue, were injected manually.Before injection of the plastic a tourniquet around the neck below the point of injection was applied.The whole body was kept in formalin overnight.The following day of injection the cranium was opened by supratentorial circular craniotomy and arcuate suboccipital craniotomy and the entire brain including the dura was removed.The dura and sinuses were preserved on the surface of the brain The brain removed from the cranium was fixed in 10 percent formalin for two to twelve weeks.After fixation the dura, arteries and pia-arachnoid were prepared, leaving the venous trees.The veins of the mesencephalon and cerebellum were then anatomically studied.Ten cases of the cerebellopontine angle tumors were then studied, comparing the phlebograms of the vertebral angiography with the operative findings.Displacement of the veins of the posterior cranial fossa caused by the tumor itself, by deformity of the brain stem, and by tonsillar herniation, in considering the size of the tumors, were described in detail.Results: This method of plastic venous injection was very valuable for studying the topographic anatomy of veins of the posterior cranial fossa.The veins of the posterior cranial fossa were divided into three major groups, anterior, superior, and inferior group .The anterior group, of which the petorosal vein was the most prominant vein, drains the anterior portion of the brainstem and cerebellum and empties mainly into the superior and inferior petrosal sinuses.