Mobile Myxopapillary Ependymoma with Associated Filum Terminale Cyst

BACKGROUND: Intradural ependymal cysts are benign, fluid-filled cysts usually situated along the ventral surface of the spinal cord. There are previous reports of 19 intradural cysts in the literature, including one cyst of the filum terminale. Here, we report for the first time the presence of a radiographically occult filum terminale cyst associated with a myxopapillary ependymoma. We propose that mobility of the tumor may provide indirect evidence of the presence of a cyst. CASE DESCRIPTION: A 65-year-old male patient presented with a homogenously enhancing ovoid mass measuring 25 mm x 10 mm within the thecal sac at the L3 through L4 levels. Repeat magnetic resonance imaging demonstrated migration of the tumor 12 mm rostrally. Following the L2 through L4 laminectomy and resection of the intradural tumor, we identified a filum terminale ependymal cyst superior to the tumor, which was also resected. CONCLUSIONS: Ependymal cysts associated with spinal tumors are rare and may be radiographically occult. The change in cyst size may explain tumor mobility. Complete resection of the cyst and histopathologic analysis is recommended to differentiate between ependymal cyst and cystic tumor tissue.