[A Surgical Case of Anaplastic Ependymoma Involving a Bridging Vein that Drained Directly into the Occipital Sinus].

INTRODUCTION: The draining veins of the brain stem and cerebellum commonly drain into the petrosal vein and sigmoid sinus, and often drain into the marginal sinus in the caudal part of the posterior fossa. Here, we report a rare case of anaplastic ependymoma involving a bridging vein that drained directly into the occipital sinus.

CASE DESCRIPTION: A 6-year-old boy was admitted to our hospital with a 1-month history of nausea, headache, and dizziness. Magnetic resonance imaging(MRI)revealed a markedly enhanced fourth ventricular tumor and obstructive hydrocephalus. Surgical removal was performed via a midline suboccipital approach. When opening the dura, we observed a bridging vein that directly connected the brain stem and the tumor with the occipital sinus. Therefore, the Y-shaped dura mater incision was not inverted, and the tumor was totally removed while preserving the draining vein. After the operation, the patient's clinical course was uneventful. The pathological diagnosis was anaplastic ependymoma(WHO grade III). Subsequently, the patient received radiotherapy and was discharged without any neurological deficits 9 weeks after the operation. At 10 months after the initial surgery, the tumor recurred on the fourth ventricle floor. Thus, we performed a second surgical procedure and noted that the bridging vein had regressed.

CONCLUSION: We report a rare draining vein that directly connected the brain stem to the occipital sinus. The tumor was removed without sacrificing this vein. Since the draining system of the posterior fossa is sometimes very complicated, we need to pay attention to it during the pre- and intra-operative periods.